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INNOVATIVE STRATEGIES FOR MANAGING RESERVOIR SEDIMENTATION IN JAPAN SEE PAGE 100

SILTING OF RECHARGE DAMS IN OMAN SEE PAGE 115

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RESERVOIR SEDIMENTATION PART 2

98 hydrolink number 4/2018

The last issue of Hydrolink focused on reservoirsedimentation with articles on the problems experi-enced in different parts of the world and themitigation measures taken in response. Becauseof the large interest among IAHR members and thebroader water resources management community,the current issue includes more articles on thesubject where researchers and other technicalexperts from different countries share their viewson how to deal with this problem. This is thesecond of three issues of Hydrolink focusing on thechallenges related to reservoir sedimentation andaiming at disseminating knowledge and lessonslearned on successful sediment managementstrategies.

As already mentioned in several of the articlespublished in the previous issue, sedimentation reduces reservoir storage capacityand the benefits derived therefrom, such as flood and drought control, water supply,hydropower, irrigation, groundwater recharge, fish and wild life conservation, andrecreation. In addition, the sediment imbalance throughout the water system causedby dams operated without sediment management facilities (e.g.bottom outlets,spillways, bypass tunnels) leads to significant infrastructure and environmentaldamages both upstream and downstream of the reservoir.

The traditional approach in the design of reservoirs was to create a storage volumesufficiently large to contain sediment deposits for a specified period, known as theeconomic life of the project or “design life” (typically 50 or 100 years). After their“design life” is reached, dams and reservoirs would have to be taken out of service,leaving future generations to have to deal with dam decommissioning and thehandling of the sediments. Yet, dam decommissioning is getting costlier and removalof deposited sediment is not a simple task, because the volume of depositedsediment in a reservoir over its design life can amount to millions, if not billions, ofcubic meters[1]. For example, the net cost of decommissioning the Tarbela Dam inPakistan, whose storage capacity as of last year had been reduced by 40% due tosedimentation[2], according to one estimate is US$2.5 billion[1]. Dam owners andoperators have therefore strong interest in finding ways for extending the life of reser-voirs, continuing to generate economic and social benefits even if they are not aslarge as in the original condition of the project.

With increasing demand for water supply and hydropower, aging infrastructure,coupled with the limited number of feasible and economical sites available for theconstruction of new reservoirs[1], the importance of converting non-sustainable reser-voirs into sustainable elements of the water infrastructure for future generations isevident. While the 20th century was concerned with dam reservoir development, thecurrent century needs to focus on reservoir sustainability through sedimentationmanagement[3]. Solutions are needed for the removal of both fine sediments (clayand silt), as well as coarse sediments (sand and gravel).

It is possible to manage reservoir sedimentation by using one or more techniques[4].The three main strategies for dealing with reservoir sedimentation are:

(1) reducing incoming sediment yield into reservoirs through watershedmanagement, upstream check dams and off-channel storage;

(2) managing sediments within the reservoir through suitable dam operating rulesfor protecting the intakes from the ingress of sediments, tactical dredging in thevicinity of the dam outlets, and the construction of barriers to keep the outletsclear; and

(3) removing deposited sediment from reservoirs by flushing, sluicing, venting of asediment-laden density current, bypass tunnels, dredging, dry excavation orhydrosuction.

Each technique has its advantages and short-comings in terms of cost, applicability and environ-mental impacts, as described by Kondolf andSchmitt in the previous issue of Hydrolink. A perfectlysustainable strategy for every situation does not exist,but efforts can be optimized for the particular condi-tions of each reservoir. In the current issue, examplesof operations and strategies are given from Japan bySumi and Kantoush and from Taiwan by Wang andKuo, showing that current and new facilities need tobe designed, re-operated, and/or retrofitted to limitthe loss of reservoir capacity due to sedimentation.Both articles provide lessons to help guide planningand design of new dams, and establish designstandards for sustainable reservoir management.

An example of a specific field case is presented in the current issue by Peteuil whodescribes a successful example of sediment management in cascade reservoirdams on the Rhône River from the Swiss border to the Mediterranean Sea. Sedimentis managed in reservoirs and channels of the Upper Rhône by flushing, such thatthe opening of the gates for the sediment release is coordinated from dam to dam.Routing and regulation of fine suspended sediment concentrations discharged fromthe upper Swiss reservoirs are performed in the French Génissiat reservoir where thedam is equipped with three outlets. The sediment flushing is conducted underextremely strict restrictions on suspended sediment concentrations. This “environ-mentally friendly flushing” from the Génissiat Dam limits the potential adverse impactsto the downstream environment (e.g. aquatic life, restored side-channel habitats)and water supply intakes. An interesting analysis of the effects of sediment flushingis presented in the article by Castillo and Carrillo who investigated the morphologicalchanges in the Paute River (Ecuador - South America) as a result of the futureconstruction of the Paute - Cardenillo Dam and associated sediment flushing opera-tions.

Water resources are limited in arid counties. In the case of the Sultanate of Oman,recharge dam reservoirs are widely used for enhancing groundwater resourcesthrough making use of stored flood waters, which otherwise would have flowed tothe sea and or spread in the desert. These reservoirs are facing, however, seriousproblems of sedimentation, which reduces their storage capacity and decreases therate of water infiltration in the subsurface, as described by Al-Maktoumi in the currentissue. The same article discusses different measures for dealing with this problem.

Some of the problems associated with reservoir sedimentation are studied bydifferent research organizations. For example, at the Laboratory of Hydraulics,Hydrology and Glaciology (VAW) of ETH Zurich, Switzerland, field, laboratory andnumerical research projects on reservoir sedimentation are conducted. Researchtopics cover reservoir sedimentation in the periglacial environment under climatechange, hydroabrasion of sediment bypass tunnels, and transport fine sedimentthrough turbines as countermeasure against reservoir sedimentation. More detailson these challenging research programs are given by Albayrak et al. in the currentissue.

The U.S. Army Corps of Engineers (USACE) is continually sharing its sustainablereservoir management knowledge base. An example of such effort is given by Shelleyet al. in this issue, illustrating a collaboration between reservoir sedimentation expertsfrom the USACE and the Government of Lao People’s Democratic Republic (LaoPDR). The overall goal of this collaboration is to improve the environmental and socialsustainability of hydropower development in the Mekong River Basin.

References[1] Pakistan Observer (2018), Tarbela Dam storage capacity reduced by 40.58pc since operation: Senate

told, August 29, 2018[2] Palmieri, A., Shah, F., Annandale, G.W., Dinar, A. (2003). Reservoir conservation: The RESCON

approach. Vol. I, Washington DC, The World Bank.[3] George, M.W., Hotchkiss, R.H., Huffaker, R. (2016). Reservoir Sustainability and Sediment

Management. Journal of Water Resources Planning and Management, 143 (3),doi:10.1061/(ASCE)WR.1943-5452.0000720.

[4] Annandale, G.W., Morris, G.L., Karki, P. (2016). Extending the Life of Reservoirs: Sustainable SedimentManagement for Dams and Run-of-River Hydropower. Directions in Development - Energy and Mining;Washington, DC: World Bank.

Angelos N. FindikakisHydrolink Editor

Kamal El kadi AbderrezzakGuest Editor

RESERVOIR SEDIMENTATION: CHALLENGES AND MANAGEMENT STRATEGIESEDITORIAL BY KAMAL EL KADI ABDERREZZAK & ANGELOS N. FINDIKAKIS

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Luis Balairon • CEDEX –Ministry Public Works, Spain

Jean Paul Chabard • EDF Research & Development,France

Yoshiaki Kuriyama • The Port and Airport Research Institute, PARI, Japan

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Ole Mark • DHI, Denmark

Rafaela Matos • Laboratório Nacional de Engenharia Civil, Portugal

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Karla González Novion • Instituto Nacional de Hidráulica,Chile

ISSN 1388-3445

Cover picture: Wujie Reservoir on the Zhuoshui (alsospelled Choshui) River in Taiwan; construction of the damwas completed in 1934; photograph taken in early 2018.(Courtesy Hsiao-Wen Wang, Department of Hydraulic and Ocean Engineering, National Cheng Kung University)

EDITORIAL ................................................................................98

INNOVATIVE STRATEGIES FOR MANAGINGRESERVOIR SEDIMENTATION IN JAPAN...........100

RESEARCH PROJECTS ON RESERVOIRSEDIMENTATION AND SEDIMENT ROUTING AT VAW, ETH ZURICH, SWITZERLAND ......................................................................105

RESERVOIR SEDIMENTATION MANAGEMENT IN TAIWAN...........................................108

SUSTAINABLE MANAGEMENT OF SEDIMENT FLUXES IN THE RHÔNE RIVERCASCADE ..................................................................................112

SILTING OF RECHARGE DAMS IN OMAN:PROBLEMS AND MANAGEMENT STRATEGIES ..........................................................................115

SEDIMENTATION AND FLUSHING IN ARESERVOIR – THE PAUTE - CARDENILLO DAM IN ECUADOR ..............................................................118

IAHR EVENTS CALENDAR ...........................................121

BUILDING RESERVOIR SEDIMENT MODELING CAPABILITIES WITH THE LAO PDR MINISTRY OF ENERGY AND MINES...........122

COUNCIL ELECTION 2019 – 2021...........................125

IAHR AWARDS - CALL FOR NOMINATIONS 2019................................126

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Technical Editors:Joe ShuttleworthCardiff University

Sean MulliganNational Universtityof Ireland Galway

RESERVOIRSEDIMENTATION PA

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The major threat to extend the life expectancy ofdams in Japan is reservoir sedimentation.Upgrading and retrofitting aging dams ismandatory to maintain their purposes and safetyover the productive life cycle. A perfectlysustainable solution for every situation does notexist, but it is essential to select a sedimentmanagement strategy appropriate for the partic-ulars of each reservoir, considering both thesedimentation issues in the reservoir andenvironmental conditions in the channelsdownstream of the dam. The key criteria aretiming of implementation and an appropriatecombination of viable sediment managementstrategies.

Reservoir sedimentation issues inJapanIn Japan, there are more than 2700 operatinglarge dams, i.e. dams higher than 15 m, with amedian age of 61 years. Among them, 900dams have reservoir volumes larger than onemillion m3 (1 Mm3). The total reservoir storagecapacity remains, however, limited,approximately 23,000 Mm3. The sediment yieldis relatively high due to the topographical,geological and hydrological conditions of thedrainage basins. Based on annual data from877 reservoirs, the sediment yield rate wasfound to range from several hundred to severalthousand m3/km2-year. The annual storagecapacity loss due to reservoir sedimentation islow, approximately 0.24%, with a high averageof 0.42% in the high mountainous central Japanregion that is on tectonic lines[1]. Figure 1 showsthe reservoir capacity loss due to sedimentation(i.e. sedimentation volume/reservoir grossstorage capacity) over the dam age. Thecumulative storage loss due to sedimentationreaches 60% to 80 % in some hydroelectricreservoirs operating for more than 50 years.Multi-purpose reservoir dams show lesssedimentation losses, i.e. 20% to 40 % ingeneral.

The aging of dams and continuous loss of waterstorage capacity due to sedimentation, coupledwith increasing environmental needs, have

INNOVATIVE STRATEGIES FOR MANAGING RESERVOIR SEDIMENTATION IN JAPANBY TETSUYA SUMI AND SAMEH A. KANTOUSH


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Figure 1. Evolution of thereservoir sedimentation rate overdam’s age. (MLIT: Ministry ofLand, Infrastructure, Transportand Tourism, P.G.: PrefecturalGovernment, JWA: Japan WaterAgency)

Figure 3. Location map of the Dashidaira Dam (high: 76.7 m, initial storage capacity: 9 Mm3, annualsediment inflow: 0.62 Mm3) and the Unzauki Dam (high: 97 m, initial storage capacity: 24.7 Mm3,annual sediment inflow: 0.96 Mm3). Photos show the two dams during a coordinated sedimentflushing operation

Figure 2. Plot of projects inJapan with different sedimentmanagement strategies.Reservoir life is indicated bythe ratio between the reservoirstorage capacity and the meanannual inflow sediment to thereservoir (CAP/MAS). Theresidence time of water (calledalso retention time,impoundment ratio) is definedas reservoir capacityvolume/mean annual riverinflow to the reservoir(CAP/MAR)

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The Dashidaira dam was completed in 1985 bythe Kansai Electric Power Co, Ltd., and theUnazuki Dam, 7 km downstream, wascompleted in 2001 by the Ministry of Land,Infrastructure, Transport and Tourism.Dashidaira and Unazuki were the first dams inJapan fitted with full-scale sediment flushingfacilities (bottom outlets, gates) in place ofhandling the incoming sediments over the next100 years without affecting the operation of thedam. These two in-series dam reservoirs arefacing extremely large amounts of sedimentinflow compared to their gross storagecapacities. The large flood event in 1995 led tothe accumulation of 7.34 Mm3 of sediment inthe Dashidaira Reservoir, which corresponds toalmost 82% of its initial storage capacity.

Sediment management at both reservoirs aimsat sustaining their original functions (e.g. floodcontrol, power generation) and maintaining

sediment routing through the basin system tothe coastal area where beach erosion isgradually progressing. The first sedimentflushing operation was conducted at theDashidaira Dam in 1991. Due to limitedexperience in the flushing process, theoperation was conducted in winter during lowflows. Subsequently, the accumulated sedimentwithin six years was flushed downstream to theestuary zone. The flushed sediment was rich inorganic matter, resulting in many negativeimpacts on the aquatic environment[4]. Since1995, the flushing operation has beenperformed every year during the first major floodevent in the rainy season from June to July. Astable flushing channel in the reservoir hasdeveloped from these operations[5]. Since 2001,the Dashidaira and Unazuki dams are operatedin sequential coordination almost annually, withhigh runoff triggering flushing of the upstreamDashidaira dam and sluicing through the

caused growing concerns on social, economic,and environmental fronts[2]. Preventing theaccumulation of sediment in multi-purposereservoirs is a key issue for sustainable use ofthe resource and to safeguard the riverenvironment.

Japan is a world leader in the variety ofimplemented sediment managementtechniques, such as trapping sediments bycheck dams (i.e. Sabo), dredging, sluicing (i.e.sediment pass-through), flushing, bypassing,and adding sediments to river channels belowdams (i.e. gravel augmentation orreplenishment). Figure 2 illustrates the range oftechniques implemented in Japan. More thanone technique may be applied at a givenreservoir, either sequentially or concurrently,depending on the reservoir’s hydrologiccapacity. Supplying the excavated gravelmaterial to reaches below dams to supportdevelopment of bars and other complexchannel features, which are essential for theflora and fauna of the aquatic environment, iswidely promoted and used in Japan[3].

Currently, reservoir sedimentation managementin Japan is entering a new stage from twoperspectives[3]. First, in contrast to conventionalcountermeasures, such as dredging and dryexcavation, sediment flushing and bypasssystems are being progressively introduced withthe aim of radically abating sediment depositionin reservoirs. Secondly, integrated approachesfor restoring effective sediment transport in therouting system, from mountains to coastalareas, is being initiated. However, sedimentflushing and bypassing have only been appliedin a limited number of cases; further studies areindeed required. This article describes examplesof sustainable sediment managementtechniques by flushing in the Dashidaira andUnazuki dams in the Kurobe River, sluicing inthe Mimi River, and by adding gravel to the riverbelow dams (i.e. sediment replenishment/augmentation).

Coordinated flushing and sluicingoperations in the Kurobe RiverThe Kurobe River on the eastern ToyamaPrefecture is a typical steep river, 85 km long fora drainage area of 682 km2. The average annualrainfall and total sediment yield are 4000 mmand 1.4 Mm³/year, respectively. The river is oneof the most important rivers in Japan due to thecascade reservoir system constructed along thewatercourse and the considerable power energyproduced (Figure 3).

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Figure 4. Flushing and sluicingoperations in the Dashidairaand Unzauki dams

Figure 5. Coordinated flushingat reservoirs in the KurobeRiver, 1–3 July 2006[6]. Inflowand outflow hydrographs andreservoir stage for (a)Dashidaira and (b) Unazukidams. (c) resultant suspendedsediment (SS) concentrations.Shimokurobe is near the riveroutlet at Japan Sea

graphic incomplete?


downstream Unazuki dam with minimalsediment redeposition.

When a flood inflow discharge exceeds 300 m3/s(250 m3/s in some particular cases) at theDashidaira Dam for the first time of the yearbetween June and August, a coordinationsediment flushing is performed. When a floodinflow discharge exceeds 480 m3/s at theDashidaira Dam after sediment flushing,sediment sluicing is performed. Theseoperations are conducted in coordination withthe Kurobe River Sediment Flushing EvaluationCommittee and the Kurobe SedimentManagement Council, monitoring the naturalflow and sediment discharges in the riverdownstream of the dams. The flushing/sluicingoperations are followed by release of a clear-water “rinsing” flow to remove accumulatedsediment from the river downstream (Figure 4).The duration of the free-flow sediment flushingoperation depends largely on the target amountof sediment to be flushed out, which is plannedbefore the sediment flushing operation.

During the flushing/sluicing operations, detailedmonitoring programs are conducted at threemajor stations downstream where the watertemperatures, pH, Dissolved Oxygen (DO),turbidity, and Suspended Sedimentconcentration (SS) were monitored on an hourlybasis. Figure 5 illustrates results from theflushing operation of July 2006 when a free-flowcondition was maintained for 12 h, removing out

240,000 m3 of deposited sediment. During thefree-flow flushing period, the maximummeasured SS was approximately 30,000 to50,000 mg/l depending on the sedimentaccumulation volume in the previous year andthe reservoir drawdown speed. No harmfulwater quality data was recorded. The coordinated flushing operations have beenefficient in reducing the reservoir sedimentation(Figure 6). From 1991 to 2014, the aggregatedvolume in the Dashidaira Reservoir increasedonly by 9% to 4.29 Mm3 and 88% of all incomingsediments were flushed. The DashidairaReservoir is currently at an equilibrium state andthe amount of sediment passing through thedam outlets is approximately 1 Mm3/year. In theUnazuki Reservoir, the flushing and sluicingoperations have removed 73% of the totalsediment inflow which is mainly composed ofmaterial less than 2 mm in diameter. Coarsematerial, larger than 2 mm in diameter andflushed from the Dashidaira Reservoir orsupplied by a tributary of the river, is mostlytrapped behind the dam; only 10% isflushed/sluiced downstream. The UnazukiReservoir is not at an equilibrium state yet.Active sand bars have been observed in theriver channel downstream, demonstrating thepositive effects of the coordinated sedimentflushing operations. The supply of sand materialhas reversed the bed armoring downstream ofthe dams, creating bed forms with high aquatichabitat value, especially for fish. The rinsingdischarge from both dams prevents excessive

accumulation of fine sediment on the sand barsafter the flushing and sluicing operations.Upstream of the dams, the flushing operationsensure that the surface layer of accumulatedsediment is continually replaced with freshsediments, decreasing the organic materialsand the eutrophication indices. Finally,evacuation channels have been prepared asshelters for many species of fish in the river,such as Ayu (Plecoglossus altivelis), during thehigh turbidity periods due to flushing operations.For more details, readers may refer to the worksby Sumi et al.[8] and Minami et al.[9].

Kamishiiba 1955 110 91.5 12.6 217.8

Iwayado 1942 57.5 8.3 5.6 77.2

Tsukabaru 1938 87 34.3 7.0 91.8

Morotsuka 1961 59 3.5 1.1 20.3

Yamasubaru 1932 29.4 4.2 2.6 32.0

Saigo 1929 20 2.4 1.0 12.0

Ouchibaru 1956 25.5 7.5 1.9 33.8

Dam Service Height (m) Initial Total sedimentation Annual sediment year capacity (Mm3) volume (Mm3) volume (103m3)


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Figure 6. Measured longitudinal profiles beforeand after flushing operations[7]. (a) DashidairaReservoir, (b) Unazuki Reservoir

Table 1. Dams and reservoir sedimentation in the Mimi River

Figure 7. Dams and power plants along the Mimi River Basin[10]

Tetsuya Sumi is Professor at theWater Resources ResearchCentre, Disaster PreventionResearch Institute (DPRI), KyotoUniversity, Japan. His specialtiesare hydraulics and damengineering, with particularemphasis on integrated sediment

management for reservoir sustainability and theimprovement of river basin environment.

Sameh A. Kantoush is AssociateProfessor at Disaster PreventionResearch Institute (DPRI), KyotoUniversity, Japan. He received hisPhD. in civil and environmentalengineering at the Federal Instituteof Technology in Lausanne(EPFL), Switzerland. His research

interests span the fundamentals of shallow flow andsediment transport, Wadi flash floods, sustainability inreservoirs, and transboundary rivers.


exceeded the designed flood for all sevendams. Power plants at Kamishiiba, Tsukabaru,Yamasubaru and Saigou were flooded renderingpower generation impossible, while Tsukabaru,Yamasubaru and Saigou dams wereovertopped and their dam control facilitiesflooded. The flood damage was amplified bytremendous landslides in 500 locations,delivering huge volumes of sediment andwoody debris. A total of 10.6 Mm3 of sedimentflowed into the river system, with approximately5.2 Mm3 being deposited in the dam-regulatingreservoirs (Table 1). Since an additionalsediment volume, approximately 26.4 Mm3,remained in the upper part of the river basin, thebasin management authority had to seriously

Upgrading and retrofitting ofCascade Dams in Mimi RiverThe Mimi River is in the southeast of Kyushu inMiyazaki prefecture, Japan (Figure 7). The riveris 94.80 km long for a drainage area of 884.1km2. Seven dams and hydropower plants wereconstructed in the Mimi River System between1920 and 1960: Kamishiiba, Iwayado,Tsukabaru, Morotsuka, Yamasubaru, Saigo, andOuchibaru dams. These dam reservoirs weredesigned to have a capacity to store 100 yearsof sediment in the deepest parts close to thedams.

In September 2005, Typhoon Nabi caused aheavy rain event, generating a flow volume that

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address this imminent threat. After detaileddiscussions among several stakeholders, a“Basin Integrated Sediment Flow ManagementPlan for the Mimikawa River” was established inOctober 2011 by the Miyazaki Prefecture. The management plan defined the work to becarried out and the roles of stakeholders, withthe aim of resolving problems caused bysediment in the basin. The Kyushu ElectricPower Company (KEPCO), which is responsiblefor the dam cascade operation, retrofitted theexisting spillway gates of selected dams so thatsediment sluicing operations by partialdrawdown could be conducted during floodevents[10]. At the Yamasubaru Dam, the spillwaycrest was lowered by partially reducing theheight of the weir section by 9.3 m; sluicingoperations have started since 2017. At theSaigou Dam, the 4.3 m lowering of spillwaycrest is almost achieved (Figure 8).

Sediment replenishment in JapaneseRiversAs a common practice in Japan, low checkdams upstream of reservoir deltas have widelybeen implemented to trap sediment (i.e. sand,gravel). The trapped sediment is regularlyexcavated mechanically, and traditionally usedas construction material. To compensate for thelack of sediment supply downstream of dams,the excavated material has been recentlysupplied to the channel, where it can bemobilized by natural or artificial floods in barsand riffles, which have high habitat value[12]. Inmost cases, sediment replenishment is focusingboth on reducing the reservoir sedimentationand on enhancing river channel improvements,i.e. detaching algae on the riverbed material[13],creating new habitats for spawning and otherfish life-stages.The annual volume of excavated sediment thatis supplied downstream of more than 27 damsin Japan remains limited (i.e. between 0.1% to10% of annual reservoir sedimentation) andinsufficient to make up for the sediment deficitcaused by the construction of the dams[12]. InJapan, sediment augmentation is commonlydone as sand/gravel deposition along themargins of the river, where it can be mobilizedby high flow (i.e. high-flow and point-barstockpiles)[14], preventing therefore artificialturbid flow that is released through the side bankerosion at low flows (Figure 9). The grain sizedistribution of replenished sediment depend onthe location of the check dams and on theecological sensitivity of the river downstream ofthe dam which may restrict the addition ofspecific sediments (e.g. fine particles).


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Figure 8. Existing and upgraded states by cutting down the crest of spillways of (a) Yamasubaru dam(two spillways retrofitted into one) and (b) Saigou Dam (four spillways retrofitted into two)[11]

Figure 9. Sediment replenishment projects in Japan. (a) High-flow Stockpile, and (b) Point bar Stockpile


Detailed monitoring of pre- and post-sedimentsupply is carried out to analyze the impact ofsuch sediment augmentation on the riverbeddynamics, benthic organisms, and algae. Someof the sediment replenishment projects havehad positive impacts when supplied sedimentswere redistributed during high flows. Moredetails are given by Kantoush et al.[12,14].

Future directionsIn Japan, plenty of dams are facing the problemof sedimentation in the deep, middle, andupstream tail-water parts of their reservoirs.Different sediment management methods maybe suitable for each part of the reservoir, suchas excavating, dredging, bypassing, flushingand sluicing. The present article highlighted theneed for retrofitting and upgrading aged dams,planning adequately flushing and sluicingoperations and adding sediment to the channeldownstream of dams.

Reservoir sedimentation management in Japanis entering a new era, although there are stilltechnical problems to be solved. The Ministry ofLand, Infrastructure, Transport and Tourism ofJapan[15] has released “The New Vision forUpgrading under Dam Operation”. This initiativeencourages sediment management projectsand contributes to international technicalcooperation projects based on the experiencesand lessons learned in Japan. A new concept and methodology should beconceived a priori to design anintergenerational, sustainable, self-supporting

rehabilitation system for river basins withreservoirs. For a complete analysis, all relevantbenefits and costs must be measured. Furtherresearch is required to guide the futuremanagement of aging Japanese dams and tosupport the huge investment that will berequired. Important research areas includereservoir service life issues and the necessity forupgrading and retrofitting aging dams. Thepresent research areas should be extended toinclude a thorough assessment of the climatechange impact and determination of theecosystem response to sediment trapping inreservoirs. A critical study of the socialdimension and effects of interventions is alsoessential for adequate sediment management.

To achieve reservoir sustainability anddownstream environmental improvements,various disciplines should be involved in therestoration project. Modification of flow andsediment transport downstream of dams altersthe geomorphic patterns which are crossrelating to habitat degradation. It is important tobetter understand the interactive processesbetween input changes on flow regime andsediment supply and the output consequencesof these changes on the biodiversity andmaterial cycles. Figure 10 brings these factorstogether to clarify the river managementobjectives. For the purpose of river restoration,suitable habitat and translated geomorphicpatterns fitting the management objectivesshould be defined. n

References[1] Sumi, T. (2006). Reservoir sediment management measures and

necessary instrumentation technologies to support them. 6thJapan-Taiwan joint seminar on natural hazard mitigation, Kyoto,Japan.

[2] Kantoush, S.A., Sumi, T. (2016). The Aging of Japan’s Dams:Innovative Technologies for Improving Dams Water and SedimentManagement. Proc. 13th International Symposium on RiverSedimentation (ISRS), Stuttgart, Germany.

[3] Sakamoto, T., Sumi, T., Hakoishi, N. (2018). New paradigms forsediment management for reservoir and river sustainability in Japan. Hydropower and Dams, Issue 2.

[4] Sumi, T., Kanazawa, H. (2006). Environmental Study on SedimentFlushing in the Kurobe River. Proc. 22nd ICOLD Congress, Q85R16, Barcelona, Spain.

[5] Kantoush, S.A., Sumi, T., Suzuki, T., Murasaki, M. (2010). Impactsof sediment flushing on channel evolution and morphologicalprocesses: Case study of the Kurobe River, Japan. Proc. 5thInternational Conference on Fluvial Hydraulics (River Flow),Braunschweig, Germany.

[6] Kondolf, G.M., Gao, Y., Annandale, G.W., Morris, G.L., Jiang, E.,Hotchkiss, R., Carling, P., Wu, B., Zhang, J., Peteuil, C., Wang, H-W., Yongtao, C., Fu, K., Guo, Q., Sumi, T., Wang, Z., Wei, Z., Wu,C., Yang, C.T. (2014). Sustainable sediment management inreservoirs and regulated rivers: experiences from five continents.Earth’s Future, doi: 10.1002/eft2 2013EF000184. Online:http://onlinelibrary.wiley.com/doi/10.1002/2013EF000184/pdf.

[7] Kantoush, S.A., Sumi, T. (2010). River morphology and sedimentmanagement strategies for sustainable reservoir in Japan andEuropean Alps. Annuals of Disas. Prev. Res. Inst., Kyoto Univer-sity, 53, 35B.

[8] Minami, S., Noguchi, K., Otsuki, H., Shimahara, N., Mizuta, J.,Takeuchi, M. (2012). Coordinated sediment flushing and effectverification of fine sediment discharge operation in Kurobe River.Proc. 80th ICOLD Annual Meeting, Kyoto, Japan.

[9] Sumi, T., Nakamura, S., Hayashi, K. (2009). The effect of sedi-ment flushing and environmental mitigation measures in theKurobe River. Proc. 23rd ICOLD Congress, Brasilia, Brazil, Q89-R6.

[10] Sumi, T., Yoshimura, T., Asazaki, K., Kaku, M., Kashiwai, J., Sato T.(2015). Retrofitting and change in operation of cascade dams tofacilitate sediment sluicing in the Mimikawa River Basin. Proc.25th congress of ICOLD, Stavanger, Q.99–R.45.

[11] Kantoush, S.A., Sumi, T. (2016). Sediment Management Optionby Sediment Sluicing in the Mimi River, Japan. Proc. 12thInternational Conference on Hydroscience & Engineering Hydro-Science & Engineering for Environmental Resilience, Tainan,Taiwan.

[12] Kantoush, S.A. Sumi, T. (2016). Effects of SedimentReplenishment Methods on Recovering River and ReservoirFunctionality. Proc. 8th International Conference on FluvialHydraulics (River Flow), St. Louis, Mo., USA.

[13] Okano, M., Kikui, H., Ishida, H., Sumi, T. (2004). Reservoirsedimentation management by coarse sediment replenishmentbelow dams. Proc. 9th International Symposium on RiverSedimentation, Yichang, China.

[14] Ock, G., Sumi, T., Takemon, Y. (2013). Sediment replenishment todownstream reaches below dams: implementation perspectives.Hydrological Research Letters, 7(3), 54–59.

[15] The Japanese Ministry of Land, Infrastructure, Transport andTourism. (2005). Technical Criteria for River Works: PracticalGuide for Planning. http://www.nilim.go.jp/lab/bcg/siryou/tnn/tnn0519pdf/ks051903.pdf.

Figure 10. Conceptual figure for bridging between hydraulics, sediment, geomorphology, and biodiversity to achieve restoration of downstream river conditions(B/h: Channel width- flow depth ratio, RDB: Red Data Book, POM: Particle Organic Matter)[9]


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IntroductionHydropower is the most important source ofrenewable energy in Switzerland and consti-tutes the backbone of the Swiss electricitygeneration portfolio. Many reservoirs arelocated in the periglacial environment, i.e. incatchment areas of which at least 30 % isglacierized[1]. Climate change and theenvisaged transition to a more sustainableenergy supply system according to the ‘SwissEnergy Strategy 2050’ will challenge theexisting infrastructure. The retreat of manyglaciers in Switzerland may have significantimpacts on water resources, but it may alsoprovide opportunities such as new sites forhydropower reservoirs. New natural proglaciallakes have recently started to form at the

termini of a number of retreating glaciers in theSwiss Alps. These reservoirs partly formnaturally at rock rims after glacier retreat, yetsome need a man-made dam to ensure theirlong-term stability.

However, the sediment yield and dischargedownstream of retreating glaciers tend toincrease, resulting in higher reservoir sedimen-tation. For sustainable reservoir operations, it isimperative to consider reservoir sedimentationand to plan and implement effective counter-measures. A number of field, laboratory as wellas numerical research projects at VAW of ETHZurich deal with reservoir sedimentation andassociated countermeasures. They are brieflydescribed hereafter.

Hydropower Potential and ReservoirSedimentation in the PeriglacialEnvironment Under Climate ChangeThe goal of this project was to better under-stand the effects of climate change onreservoir sedimentation and hydropower devel-opment in the Swiss periglacial environment.The study was divided into three parts, namelya systematic investigation of the hydropowerpotential in Swiss periglacial catchments, afield investigation of sediment fluxes into andinside periglacial reservoirs, and the numericalinvestigation of long-term sedimentationprocesses and patterns in such reservoirs.

In the first part, a framework based on anevaluation matrix with 16 economical, environ-

RESEARCH PROJECTS ON RESERVOIR SEDIMENTATION AND SEDIMENT ROUTING AT VAW, ETH ZURICH, SWITZERLANDBY ISMAIL ALBAYRAK, DAVID FELIX, LUKAS SCHMOCKER AND ROBERT M. BOES

Reservoir sedimentation is a global concern and is expected to aggravate in the near future due to climate changeand the linked increase in sediment availability below retreating glaciers. There is an increasing need for efficientsediment management to maintain the active storage volumes in reservoirs and to improve the continuity ofsediment transport along rivers from upstream to downstream of dams. The Laboratory of Hydraulics, Hydrologyand Glaciology (VAW) of ETH Zurich, Switzerland, has conducted several basic and applied research projects onreservoir sedimentation and possible countermeasures (e.g. sediment bypass tunnels and increased fine sedimenttransport through power waterways).

Figure 1. Griessee Reservoir with retreating glacier in the background, leading to higher sediment yield. (Photograph: D. Ehrbar, VAW, ETH Zurich)


water sample analysis, laser in-situ scatteringand transmissometry (LISST) and AcousticDoppler Current Profiler (ADCP) was applied inthe field measurements. In the last part, a 1-Dnumerical model was implemented using thesoftware BASEMENT[4] to simulate both thedelta formation of coarse sediments and thelake-wide sedimentation from non-stratified(homopycnal) flows. The model was validatedwith data from the Gebidem Reservoir and thenapplied to a potential future periglacialreservoir[2,3]. Based on the project findings,implications on future reservoir operations,considering climate change, werediscussed[2,3].

Hydroabrasion in high speed flow atsediment bypass tunnelsSediment bypass tunnels (SBTs) are aneffective routing technique to reduce reservoirsedimentation, diverting sediment-laden flowaround the dam, thus allowing the re-estab-lishment of the natural sediment continuityalong the river (Figure 2a). Moreover, SBTsenhance the operating safety of dams byincreasing the outflow capacity, which is not

sufficient anymore at many schemes[5,6,7].Despite these advantages, no guideline for thedesign and operation of SBTs is available andmany SBTs face severe invert abrasion due tohigh-speed sediment-laden flows, putting SBToperation at risk and causing high mainte-nance costs (Figure 2b). To address theseproblems, four research projects have beenconducted at VAW. The first project focused onflow characteristics, particle motion, particleand invert material properties, which aregoverning parameters of hydro-abrasion[6,8,9,10]. The study was conducted in aFroude-scaled laboratory flume modeling thephysical processes present in a straightsection of SBTs. The findings contributed to abetter understanding of the physical processesunderpinning hydro-abrasion of SBTs, and ledto the modification of an abrasion predictionmodel[10]. A second and complementary in-situinvestigation was conducted at three SwissSBTs[7]. Various invert materials were testedand the obtained data were used to calibratethe above-mentioned abrasion model.Furthermore, the field data contributed toimprove and optimize the bypass design and reservoir operations for better bypassefficiency [7]. The findings of both studies led toinitiate the third and on-going research projectentitled “Hydro-abrasion at hydraulic structuresand steep bedrock rivers”[11]. The focus of thisproject is to investigate the effects of lowaspect ratios of channel width to water depthand of sediment hardness and shape onsediment transport and hydro-abrasion in alaboratory flume, mimicking SBTs and high-gradient mountain streams. The fourth projectdealt with the morphological effects of SBToperation on downstream river reaches bymeans of a field study at the Solis SBT in theCanton of Grisons, Switzerland, and bysystematic numerical modelling of the SBTsediment pulses and their downstream effectsin terms of both bed slope development and

mental and social criteria for consistent ratingof all potential Swiss sites was developed andapplied[2,3]. These criteria include the long-termrun-off evolution, natural hazards, sedimentcontinuity, protected areas, the visibility of newdams from populated places and effects ontourism. Seven suitable reservoir sites for newpotential hydropower plants (HPPs) wereretained, which are estimated to add 1.1 TWhof electricity per year[3]. With these new reser-voirs, the intermediate goal of the Swiss EnergyStrategy for hydro-electricity in 2035, i.e. 37.4TWh/a, can be met. The infill time of all sevenreservoir is 500 years or more, although ithighly depends on the future retreat of glaciers.In the second part of the project, suspendedsediment concentration (SSC), particle sizedistribution, bathymetry and flow velocity wereinvestigated in the three Swiss periglacial reser-voirs Griessee (Fig. 1), Gebidem and Lac deMauvoisin with infill times between roughly 30and 1000 years, to better understand sedimen-tation processes and delta formation[3]. Allthree reservoirs suffers from sedimentationproblem and countermeasures are needed fortheir sustainable operation. A combination of

Figure 2. (a)Schematic view of an in-streamreservoir withsedimentbypassing[7] and(b) abradedconcrete invert ofthe Runcahez SBT,Switzerland(Photograph: M.Müller-Hagmann,VAW, ETH Zurich)

Figure 3. Increasing suspended sediment concentration (SSC) in turbine water as a countermeasure toreservoir sedimentation


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bed material composition[12]. The outputs ofthese projects contribute to establish a generalguideline for sustainable and efficient designand operation of SBTs and other hydraulic/civilstructures exposed to hydro-abrasion[5,13].

Reduction of reservoir sedimentationby increasing fine sedimenttransport through turbinesSediment flushing through dam bottom outletswith water level drawdown is a technique tomanage sedimentation problems in smallreservoirs. However, this is rarely feasible forlarge reservoirs due to important water losses.In addition, environmental regulations may limitthe admissible suspended sediment concen-tration (SSC) downstream of dams, or requestthat sediment transport is not hindered signifi-cantly by dams. An option to reduce sedimen-tation in HPP reservoirs in compliance withsuch environmental requirements is toincrease the transport of fine sedimentsthrough power waterways – and hence theturbines – to the downstream river reach[14]

(Figure 3). This has the advantages that (i) theSSC downstream of dams and powerhouses islow compared to those during occasionalreservoir flushing operations, and (ii) noflushing water is lost for electricity generation.The disadvantage of this option is that turbinesare exposed to higher sediment loads whichmay intensify hydro-abrasive wear. Turbinewear can be mitigated by appropriate turbinedesign and coatings as well as by limiting theSSC and particle sizes in the turbine water.

The topic of turbine erosion and its negativeeffects (e.g. reduced turbine efficiency,production losses, increased maintenancecosts) have been investigated since 2012 inthe scope of an interdisciplinary researchproject at the high-head HPP Fieschertal in theSwiss periglacial environment. Varioustechniques for monitoring of suspendedsediment load, turbine erosion and efficiencychanges were tested and further developed[15,16]. Based on the acquired data, ananalytical erosion model[17] was adapted andcalibrated for coated Pelton buckets[15]. Thismodel can be used to estimate acceptableSSCs and particle sizes for the option ofincreasing the fine sediment transport throughpower waterways and turbines. By this way, thenegative effects of reservoir sedimentation andturbine erosion can be balanced in order tomaximize the profitability and maintain theoperational flexibility of storage hydropowerschemes.

The sediment load in the power waterway maybe increased by hydraulic dredging (pumping)of previously settled fine sediment in thevicinity of the turbine water intakes (Figure 3).The flow rate in the dredging pipe is regulatedin such a way that the SSC in the turbine wateris acceptably low. The particle size may belimited by the suitable selection of dredgingarea (sufficiently distant from the reservoirinflow), as well as by screens or settling tankson the dredging boat.

AcknowledgementsThe authors acknowledge the Swiss NationalScience Foundation (SNSF), Swiss FederalOffice of Energy (SFOE), swisselectricresearch, Swiss Committee on Dams,Gommer kraftwerke AG, Axpo Hydro SurselvaAG, Officine Idroelettriche della Maggia SA

(OFIMA), Electra-Massa AG, Alpiq, HYDROExploitation SA, and equipment manufacturersfor their financial and/or technical supports inall mentioned projects. We also acknowledgeHochschule Luzern and Technical University ofDresden, Germany, for their collaborations. Allprojects are embedded in the framework of theSwiss Competence Centre of Energy Research– Supply of Electricity (SCCER-SoE), aninitiative funded by the Swiss Confederationthrough Innosuisse. n

References[1] Hallet, B., Hunter, L., Bogen, J. (1996). Rates of erosion and

sediment evacuation by glaciers: A review of field data and theirimplications. Global and Planetary Change 12(1-4): 213-235.

[2] Ehrbar, D. (2018). Hydropower Potential and ReservoirSedimentation in the Periglacial Environment Under ClimateChange, Doctoral Dissertation, VAW-Mitteilungen 247 (R. Boes,ed.), ETH Zurich, Switzerland. https://doi.org/10.3929/ethz-b-000301149.

[3] Ehrbar, D., Schmocker, L., Vetsch, D.F., Boes, R.M. (2018).Hydropower potential in the periglacial environment ofSwitzerland under climate change. Sustainability 10(8), 2794;https://doi.org/10.3390/su10082794.

[4] Vetsch, D.F., Siviglia, A., Caponi, F., Ehrbar, D., Facchini, M.,Gerke, E.; Kammerer, S., Koch, A., Peter, S., Vonwiller, L. (2017).BASEMENT Version 2.7; ETH Zurich: Zurich, Switzerland.Available online:http://people.ee.ethz.ch/~basement/baseweb/download/documentation/BMdoc-Reference-Manual-v2-7.pdf.

[5] Auel, C., Boes, R.M. (2011). Sediment bypass tunnel design -review and outlook. Proc. ICOLD Symposium “Dams underchanging challanges” (A. J. Schleiss & R. M. Boes, eds.), 79thAnnual Meeting, Lucerne, Switzerland: 403-412.

[6] Auel, C. (2014). Flow characteristics, particle motion and invertabrasion in sediment bypass tunnels, Doctoral Dissertation, VAWMitteilungen 229 (R. Boes, ed.), ETH Zurich, Switzerland.https://doi.org/10.3929/ethz-a-010243883.

[7] Müller-Hagmann, M. (2017). Hydroabrasion in high-speed flowsat sediment bypass tunnels, Doctoral Dissertation, VAW-Mitteilungen 239 (R. Boes, ed.), ETH Zurich, Switzerland.https://doi.org/10.3929/ethz-b-000273498.

[8] Auel, C., Albayrak, I., Boes, R.M. (2014). Turbulence character-istics in supercritical open channel flows: Effects of Froudenumber and aspect ratio. Journal of Hydraulic Engineering140(4), 04014004.

[9] Auel, C., Albayrak, I., Sumi, T., Boes, R.M. (2017). Sedimenttransport in high-speed flows over a fixed bed: 1. Particledynamics. Earth Surface Processes and Landforms, 42(9): 1365-1383.

[10] Auel, C., Albayrak, I., Sumi, T., Boes, R.M. (2017). Sedimenttransport in high-speed flows over a fixed bed: 2. Particleimpacts and abrasion prediction. Earth Surface Processes andLandforms, 42(9): 1384-1396.

[11] Demiral, D., Albayrak, I., Boes, R.M. (on-going). Hydro-abrasionat hydraulic structures and steep bedrock rivers. PhD project.http://www.vaw.ethz.ch/en/research/hydraulic-engineering/hydroabrasion-and-sediment-monitoring.html#abrasion.

[12] Facchini, M. (2017). Downstream morphological effects ofsediment bypass tunnels, Doctoral Dissertation, VAW-Mitteilungen 243 (R. Boes, ed.), ETH Zurich, Switzerland.https://doi.org/10.3929/ethz-b-000225127.

[13] Boes, R.M. Ed. (2015). Proc. First International Workshop onSediment Bypass Tunnels, VAW-Mitteilungen 232, ETH Zurich,Switzerland.

[14] Felix, D., Albayrak, I., Boes, R.M., Abgottspon, A. (2017).Sediment transport through the power waterway and hydro-abrasive erosion on turbines. Proc. Hydro 2017 Conference,Seville, Spain: paper no. 27.07.

[15] Felix, D. (2017). Experimental investigation on suspendedsediment, hydro-abrasive erosion and efficiency reductions ofcoated Pelton turbines, Doctoral Dissertation, VAW-Mitteilungen238 (R. Boes, ed.), ETH Zurich, Switzerland.https://doi.org/10.3929/ethz-b-000161430.

[16] Boes, R.M. (Ed) (2016). Proc. International workshop ‘Dealingwith hydro-abrasive erosion at high-head hydropower plants’ -28th IAHR Symposium on Hydraulic Machinery and Systems,Grenoble, France, VAW-Mitteilungen 237, ETH Zurich,Switzerland. http://www.vaw.ethz.ch/das-institut/vaw-mitteilungen/2010-2019.html

[17] IEC 62364 (2013). Hydraulic machines - Guide for dealing withhydro-abrasive erosion in Kaplan, Francis and Pelton turbines,Edition 1.0, International Electrotechnical Commission, Geneva,Switzerland.

Dr. Ismail Albayrak is a researchscientist and lecturer at theLaboratory of Hydraulics,Hydrology and Glaciology (VAW)of ETH Zurich since 2011. He received his MSc. in hydraulicengineering from Istanbul

Technical University in 2003 and his PhD in the field ofenvironmental hydraulics at the Federal Institute ofTechnology in Lausanne (EPFL) in 2008.

Dr. David Felix joined the VAW ofETH Zurich as a teaching assistantand scientific collaborator in2010. From 2012 to 2017 hefocused on the PhD-project onturbine erosion described in thepresent article. He continues

working on suspended sediment and turbine erosion asa postdoctoral researcher.

Dr. Lukas Schmocker joined thehydropower team of the SwissCompetence Centre of EnergyResearch – Supply of Electricity(SCCER-SoE) in 2014 with aresearch focus on hydropowerproduction and infrastructure

adaption. In parallel, he is working as a project managerin flood management at the consulting company Basler& Hofmann.

Dr. Robert M. Boes is Professorof hydraulic structures andDirector of the VAW at ETH Zurich.His research works focus onsustainable hydropower, reservoirsedimentation and floodpropagation, among others.

He was formally the head of the Dam ConstructionGroup at TIWAG-Tiroler Wasserkraft AG, an Austrianutility.


With many dams reaching the end of theirdesign life, sediment accumulation has becomean increasingly important stake in reservoirmanagement. Feasibility studies conducted forexisting reservoirs did not address the costs ofdam decommissioning and sedimentmanagement at the end of the design life, butthese costs are substantial, as has beendemonstrated for more than 1000 damremovals[1]. The potential benefits of managingsediment to maintain the storage capacity ofreservoirs has widely been recognized[2], but todate it has been implemented at relatively fewsites. This article summarizes sedimentmanagement strategies in Taiwan, providinglessons to help guide planning and design ofnew dams, and establish design standards forsustainable reservoir management. This articleis complementary to other articles in this and theprevious issue of Hydrolink on reservoir

sedimentation, such as those by Kondolf andSchmitt, Annandale et al., Kantoush and Sumi,Lyoudi et al. who present diverse experiencesand policies in managing reservoir sedimen-tation worldwide.

BackgroundThe island of Taiwan (36000 km2) supplies thePacific Ocean with 384 million tonnes ofsuspended sediment per year (Figure 1), whichmeans that 1.9% of the global fluvial suspendedsediment discharge is derived from only 0.024%of Earth’s subaerial surface[3]. Tectonicallysubduction zones, rapid uplifts, intensemonsoon and typhoonal rains generate rapiderosion rates that make Taiwan’s sediment yieldto be among the highest in the world.

Taiwan counts 61 major reservoirs whichimpound a total initial storage capacity of 2,200

Mm3 of water for domestic, industrial, agricul-tural and hydropower needs. However, with itshighly seasonal precipitation and erodiblelandscapes, the ability to store water is seriouslythreatened by sedimentation, calling thereforefor the implementation of sustainable sedimentmanagement strategies[4]. The annual capacityloss due to sedimentation of reservoirs in Taiwanis 22 Mm3. By 2011, almost 30% of the totalinitial capacity of reservoirs had been lostaccording to the Water Resources Agency, withsome reservoirs having lost more than 80% oftheir initial volumes. Figure 2 shows a selectionof reservoirs in Taiwan, and their correspondingsediment management strategies.For the benefit of gathering helpful informationfor existing and future reservoir sedimentmanagement, six cases, spanning a range ofriver and dam sizes, geographical contexts, andmanagement objectives, have been examined[5]

(Figures 2). These reservoirs, Shihmen,Zengwen, Ronghua, Wujie, Agongdian andJensanpei, are facing severe sedimentationproblems (Table 1 and Figure 3), therebyrequiring extensive interventions formaintaining/restoring the reservoir storagecapacity and dam functions.

SEDIMENT MANAGEMENTSTRATEGIESExamining the selected six reservoirs, throughthe perspective of sediment managementframework described by Annandale et al. (cf.first Hydrolink issue on reservoir sedimentation),some strategies were more commonly applied(Figure 2), such as reducing sediment yield fromthe catchment, trapping sediment above thereservoir by check dams (i.e. Sabo dams,Figure 4a), modifying dam operating rules, andhydraulic dredging of accumulated sedimentnear the dam. However, these practicesrepresent the ‘low-hanging fruit’, generallycharacterized by low capital costs but also havelimited effectiveness in maintaining and/orrestoring the reservoir capacity.

Table 1. Overview of case studies. Reservoirpurposes are Municipal and Industrial (M&I),Irrigation (IR), Industrial (ID), HydropowerGeneration (HP), Recreation (R), SedimentControl (SC), and Flood Control (FC). (data

RESERVOIR SEDIMENTATION MANAGEMENT IN TAIWANBY HSIAO-WEN WANG AND WEI-CHENG KUO

Figure 1. (a) Map of Taiwan and general information, (b) Monthly average rainfall from 1949 to 2017. Data courtesy of National Development Council Government Website Open Information Announcementand Central Weather Bureau


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cost of approximately US$20/m3. In contrast,turbidity current venting and sediment sluicingthrough the renovated power plant penstocks,the renovated low-level Permanent River Outlet(PRO), which releases downstream watersupply during power plant failures, and thespillway tunnel renovation projects (Figure 4c)effectively resulted in the removal of 12.6 Mm3 ofsediment in a period of 10 years (2005-2015),with a total initial engineering cost of aboutUS$67 million, for a unit cost of approximatelyUS$5/m3. Thus, the infrastructure retrofits had amuch higher economic efficiency than thehydraulic dredging.

The time horizon of sediment management is animportant metric in comparing sedimentmanagement strategies. At the Shihmen

Reservoir, dredging over 31 years removed thesame amount of sediment as the PRO, turbidityventing, and spillway tunnel did in only 8 years.The cost of the power plant modifications(US$29 million) at Shihmen to facilitate turbiditycurrent venting and sluicing, calculated over a25-year design life of the tunnel, yielded asmaller unit cost for sediment removal(US$3/m3) than did hydraulic dredging(US$20/m3). Desilting tunnels are a higheconomically efficient technique compared totraditional dredging. The planned AmupingDesilting Tunnel will require an initial investmentof US$133 million, and is expected to remove0.64 Mm3/year for a duration of 25 years of thedam operation[6]. Its total cost is thereforeUS$33 million less than the hydraulic dredginginduced cost to remove the same materialvolume.

Some of the most effective sedimentmanagement strategies (i.e. sediment bypass,sediment pass-through) were implemented atonly two sites, Shihmen Reservoir andAgongdian Reservoir. Sluicing, turbidity ventingand flushing in Taiwan’s reservoirs have beenshown to discharge only 30 to 40% of theincoming sediment, calling for the use of othercomplementary methods. Thus, dredgingcontinues to be an essential component ofefforts to prolong reservoir life.

The lack of sediment management plans andmonitoring for most of the reservoir sites isstriking. While intakes and hydraulic structureshave been refitted for the Shihmen, Zengwen,and Agongdian reservoirs, or are under consid-eration for modification for the RonghuaReservoir, only the Shihmen and Zengwen reser-voirs have comprehensive plans placing theserenovations within the longer-term context ofsediment management. For instance, a compre-hensive plan at Shihmen Reservoir (Figure 5)was developed to identify the managementstrategies that may be used over time to combatsedimentation. In addition to the currentpractices, the design of desilting tunnels fromthe reservoir itself is ongoing[7,8]. A desiltingtunnel (Amuping) will divert discharge andsediment from the midpoint of the reservoir intoa 3.7 km-long tunnel with a gradient of 2.86% totransport 0.084–0.104 mm sized sediment[6].After completing the Amuping desilting tunnel in2021, there are plans to construct theDawanping desilting tunnel to vent turbiditycurrents through two 10-m-diameter steel pipesvia an intake structure, a 0.9-km tunnel, and twooutlets, rejoining the river 1 km downstream of

courtesy of WRA, Taipower Company, andTaiwan Sugar Corporation)

In lieu of the aforementioned techniques, moreefficient approaches requiring larger up-frontcapital investments are available. Dredging isrelatively easy to implement, has low capitalinvestment requirements, and offers potentialvalue added from selling coarse aggregate foruse in construction (when there is demand forsuch material). However, the effectiveness ofdredging for maintaining the reservoir capacityrelative to the annual sediment inflow is very low.For instance, in the multipurpose ShihmenReservoir, approximately US$160 million wasspent on hydraulic dredging operations over 31years (1985 to 2015, Figure 4b), resulting inremoval of only 8.1 Mm3 of sediment at a unit

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Figure 2. Selected reservoirs and associated sediment management strategies in Taiwan[5]. The studycases are 2: Ronghua, 3: Shihmen, 7: Wujie, 11: Jensanpei, and 13: Zengwen. (data courtesy of WRA,Taipower Company, and Taiwan Sugar Corporation) (data courtesy of Water Resources Agency (WRA),Taipower Company, Taiwan Sugar Corporation, and Taiwan Water Corporation)

Table 1. Overview of case studies. Reservoir purposes are Municipal and Industrial (M&I), Irrigation (IR),Industrial (ID), Hydropower Generation (HP), Recreation (R), Sediment Control (SC), and Flood Control(FC). (data courtesy of WRA, Taipower Company, and Taiwan Sugar Corporation)

Shihmen (Dahan) 1964 M&I, IR, HP, FC, R 309 208.3 1,468 3.5 (1964–2015)

Ronghua (Dahan) 1984 HP, SC 12.4 0.9 1086 2.8 (2001–2015)

Wujie (Jhuoshuei) 1934 HP 14 0.7 1,279 1.7 (2001–2015)

Jensanpi (Chiesui) 1938 IR, ID; after 2001, only R 8.1 1.5 7 0.25 (2001–2015)

Agongdian (Agongdian) 1953 FC, IR, M&I (2011~) 36,700 17.2 54

0.38 2005 18,370 16.3 (2001–2015)

Zengwen (Zengwen ) 1973 M&I, IR, HP, R, FC 748,400 468 1,153 5.60 (1975–2015)

Reservoir (River) Service Reservoir Initial Storage Live storage Mean annual Mean Annual year purposes Capacity (Mm3) (Mm3) runoff(Mm3) inflow Sediment (Mm3)


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Strategies associated with each reservoirs1 Feitsui: AF, ME2 Ronghua: AF3 Shihmen: AF, HD, ME, SL, VT, DT4 Tapu: AF, EF, HD5 Minte: AF, HD6 Techi: AF, ME7 Wujie: AF, DF8 Wusheh: AF, ME9 Zengwen: AF, HD, ME, OS, SL, (SB), VT10 Paiho: AF, HD, ME, (SL), (SB)11 Jensanpei: AF, EF, ME12 Wusantou: AF, HD13 Agongdian: AF, EF, ME14 Nanhua: AF, ME, HD, VTDescriptionAF: AFforestationDF: Drawdown FlushingDT: Desilting TunnelEF: Empty FlushingHD: Hydraulic DredgingME: Mechanical ExcavationOS: routing Off-Stream reservoirSL: SluicingSB: Sediment BypassVT: routing Venting Turbidity currents


the dam. The two tunnels are expected toremove approximately 1.35 M tonnes/year,representing 39% of the mean annual sedimentinflow.

Suitability of sediment managementtechniquesThe characteristics of a site can stronglyinfluence the suitability of different sedimentmanagement techniques. For example, despiteits effectiveness, drawdown flushing has beenconducted during floods in the Wujie (Figure4d), Agongdian and Jensanpei reservoirs.Drawdown sediment flushing during the non-flood season is limited to hydrologically smallreservoirs, where the residence time (i.e. ratio ofstorage capacity to mean annual runoff) doesnot exceed a certain value[13]. Different valuesfor the residence time for characterizing areservoir as small have been proposed in theliterature, ranging from 0.04[14] to 0.3[15]. Inhydrologically “large” reservoirs, wheredrawdown is not an option, major infrastructuremodifications may be needed to managesediment by venting turbidity currents orbypassing incoming sediment.

Figure 4. Sediment management strategies in Taiwan[5]: (a) mechanical dredging from a sabo dam in Yixing, Shihmen basin, (b) hydraulic dredging at Shihmenreservoir (photo courtesy of WRA), (c) Sluicing at Shihmen Reservoir during Typhoon Soulik in 2013 (WRA), (d) Drawdown flushing at Wujie Reservoir

Figure 3. Reservoir sedimentation and material extraction over time[5]. The capacity loss due to sedimentation is reported along with the year of last reservoirsurvey on each plot (e.g. 33% and 2015, respectively, for Shihmen Reservoir). (a) Shihmen Reservoir; (b) Ronghua Reservoir; (c) Wujie Reservoir; (d) JensanpeiReservoir; (f) Zengwen Reservoir. (data courtesy of WRA, Taipower Company, and Taiwan Sugar Corporation). Most important events include Typhoon Gloria in1963, Typhoon Herb in 1996, Typhoon Mindulle and Typhoon Aere in 2004, and Typhoon Morakot in 2009. Due to the high sediment yield, the Wuji reservoir wasalmost filled six years after its completion in 1934

Similarly, bypass tunnels are best-adapted tosituations where the geometry of the river andreservoir make possible a steeper short-cutroute for the tunnel, such as where the reservoiroccupies a river bend. A feasibility study at theZengwen Reservoir proved that the unfavorablegeometry, the high construction cost, and theengineering difficulty make the construction of asediment bypass tunnel unlikely[16].Furthermore, understanding the interactionsbetween flow and sediment in sediment bypasstunnels is needed to avoid the need for frequentmaintenance as bedload induces abrasion ofthe tunnel concrete bed (cf. Albayrak et al.’sarticle in the current issue).

Needs for and barriers to sustainablereservoirsSustainable reservoirs, from a sedimentmanagement perspective, have been definedas those a) whose life and reservoir capacity ismaintained indefinitely, b) whose economicvalue is positive when taking a full life cycleapproach that considers dam decommissioningand sediment management at the end of theproject life, and c) provide intergenerational

equity by not burdening future generations withthe social, environmental, or economic costs ofnatural resources use by previous genera-tions[13]. All these three concepts, either directlyor indirectly, support the need for managingsediment throughout the reservoir life.

Shihmen and Zengwen are the most importantreservoirs of Taiwan, supplying more than 25%and 40% of the water demand for the northernand southern regions, respectively. However,sedimentation was not taken seriously in thesereservoirs until they lost a large portion of theirrespective capacity during a single typhoonevent (i.e. 9% of initial storage capacity lost dueto Typhoon Aere in 2004 for Shihmen Reservoir,12% of initial storage capacity lost due toTyphoon Morakot in 2009 for ZengwenReservoir). For Ronghua and Wujie, the tworeservoirs with almost no remaining storagecapacity, the originally stated design lives wereshort. For instance, the Ronghua Reservoir wascommissioned in 1984 on the Dahan River withdesign life of only 25 years, as one of the 120sediment-control dams (i.e. Sabo) reducing thesediment inflow to the Shihmen Reservoir. As of


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technical, environmental, and economic barriersall inhibit effectively addressing reservoirsedimentation. Social barriers can be local (e.g.traffic concerns, tourism impacts, flood hazards)to global (e.g. design-life engineering paradigm,disregarding intergenerational equity). Amongthem, social concern about increased floodhazard risk due to aggradation downstream ofthe dam is also a technical issue. While theevaluation of increased sediment concentrationsand aggradation of the bed downstream due tosediment passed through the bypass anddesilting tunnels were conducted for ShihmenReservoir[7,8], few such systematic evaluationsexist for other sites.

A variety of technical concerns may emerge inany individual project. The methodological andfinancial challenges associated with monitoringsediment inflows has been the most commontechnical barrier, though methods for monitoringsediment are well established[19]. The loss ofwater supply associated with sediment flushingand sediment pass-through has also been acommon technical barrier across our casestudies. The primary environmental impact ofsediment management is associated with highturbidity, even though it was identified as aconcern at only two of the sites, Shihmen andZengwen, and the literature on this impact is stillimmature. For instance, large pulse releases ofsediment during flushing operations can impactdownstream aquatic organisms through

abrasion, burial, and in cases of organicsediments, anoxia[20]. Besides, dredging isknown to impact aquatic organisms in the reser-voirs in a variety of adverse ways[21] that rangefrom direct mortality over the short term to trans-generational effects over the long term.Engineering and ecological research couldevaluate operational and mechanical sedimentmanagement based on deviations frombackground concentrations, or behavioral ortoxicity thresholds for aquatic organisms[22]. Themost obvious economic impacts are associatedwith the capital costs of modifying water infra-structure to accommodate sediment pass-through, but ancillary impacts, such as foregonehydropower revenue, may also pose realbarriers to implementing some of the mostsustainable sediment management solutions. Itis worth noting that the most commonlyidentified conflicts (e.g. design-life, capitalcosts, monitoring, impacts to water supply) tendto be addressed by more short-term strategies(e.g. mechanical dredging, check dams)instead of implementing long-term solutions(e.g. infrastructure retrofits).

ConclusionGiven the high sediment yield, several strategiesfor managing reservoir sedimentation have beenimplemented in Taiwan, offering insights intotheir effectiveness, tradeoffs, and barriers. Theselected case studies highlight the socialbarriers to reservoir sustainability, including thecrisis-response approach to addressingsedimentation and the low priority for sediment

2003, the reservoir was almost filled withsediment and its remaining capacity as of 2014was less than 1% (Figure 3b). For dams whoseprimary objective was sediment retention, theexpected timeframe for their benefit has beenshort. Moreover, sediment-filled dams can eitherfail catastrophically[17] or become expensiveengineering problems upon decommis-sioning[18], creating hazards and burdens forfuture generations. Reservoir sedimentationdemonstrates the critical need to take a full lifecycle approach during design and constructionof any dam, accounting for decommissioningand sediment management at the end of theproject life.

For Agongdian and Jensanpei, the two reser-voirs where drawdown flushing operations areconducted, conflicts with the competing use thereservoirs for recreation led managers to decideagainst emptying them. Public education on theimportance of sediment flushing may helpreduce conflicts between recreational andsedimentation operations. However, this mustbe complemented by strong leadership fromreservoir managers and politicians to ensurethat the key benefits of flood regulation andwater supply are not compromised by thepromotion of tourism and recreational activities.

Classifying the conflicts associated withsustainable sediment management in theTaiwan case studies highlights how social,

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Hsiao-Wen Wang is AssociateProfessor at Department ofHydraulic and Ocean Engineeringof the National Cheng KungUniversity. Her research interestsinclude hydraulics, sedimenttransport and management,

river restoration and ecohydraulics. She is now a visitingscholar at UC Berkeley through the Fulbright SeniorResearch Program working on resolving the conflictsrelated to land use between green energy and other corenecessities for environmental sustainability.

Wei-Cheng Kuo is PostdoctoralResearch Fellow at Department ofHydraulic and Ocean Engineeringof the National Cheng KungUniversity. His research interestsinclude hydraulics, sedimenttransport and management, and river restoration.


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Continues in page 117

Figure 5. Diagrammatic map showing management strategies at Shihmen Reservoir[5]. Data are from WRA[9-12]


The Rhône is one of the major river systems ofEurope. Originating in the Swiss Alps, it flowsmainly through France to the MediterraneanSea. At the catchment outlet, the mean annualdischarge is approximately 1,700 m³/s for abasin area of 95,500 km². Compared to similarcatchments, the Rhône River is quite steep andits flow discharge is significant. A powerfulwaterway, the Rhône River is not only a sourcefor hydropower generation but also a carrier ofsediment.

The Rhône River cascade:background and challengesThe French State entrusted the concession ofthe Rhône River in 1934 to CompagnieNationale du Rhône (CNR) to fulfil three objec-tives for the benefits of the national community:hydroelectricity production, navigation devel-opment and management, and irrigation. CNR

is France’s leading producer of 100 %renewable energy (water, wind, sun), with a totalinstalled capacity of approximately 3,700 MWincluding a cascade of nineteen (19) dams andhydropower plants from the Swiss border to theMediterranean Sea (Figure 1). The companyproduces 25% of France’s hydroelectricity, andmanages a concession covering 27,000hectares in the Rhône Valley and 330 km ofwide-gauge navigable waterways. CNR hasconceived a redistributive business modelbased on the River Rhône managementwhereby green electricity production iscombined with territorial development[1].

Except for three dams including the Génissiatdam on the French Upper Rhône (i.e. betweenSwiss border and the city of Lyon), allhydropower developments operated by CNRare run of the-river short-circuiting the natural

river course through a side canal[2] (Figure 2).Typically, run of the river facilities include abarrage built across the river mainstream thatdiverts the major portion of the flow through aheadrace canal towards the power plant. Tomaintain suitable conditions for aquatic life, anecological flow discharge is released into thenatural river course through one of the damoutlets. The reservoir storage capacity of run-of-the-river dams is negligible compared to riverflow volumes, especially during flood condi-tions. Neither inter-annual nor seasonalregulation is thus possible because the wateroutflow is very close to the water inflow.On the Rhône River cascade, CNR has to copewith several sedimentation-related constraints,among them the facilitation of sediment routingloads arriving at inlets of reservoirs. Significantquantities of sediments are supplied to reser-voirs during flood periods or flushing events

SUSTAINABLE MANAGEMENT OF SEDIMENT FLUXES IN THERHÔNE RIVER CASCADEBY CHRISTOPHE PETEUIL

Figure 1. Map of CNR hydraulic assets in and outside of the Rhône River valley (left) and general information on CNR mainstream dams (right)


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upper Swiss reservoirs are performed by CNRin the Génissiat reservoir (23 km long, storagecapacity of 56 Mm3) where the dam isequipped with three outlets (Figure 3): a bottomgate (LLO), an outlet at halfway up the dam(ILO), and a surface spillway (HLO).First, the water surface in the Génissiat reservoiris lowered at specific levels in order toremobilize the sediments previously depositedand to ensure the routing of inflowingsediments discharged from the upper Swissreservoirs. Inflowing sediments could entirelysettle if the water level in the reservoir is toohigh, while huge sediment concentrations maybe released downstream of the dam if the waterlevel is too low. Secondly, an appropriate gateopening program and mixing of the sediment-laden flows released by each of the three

outlets (i.e. mixing water with high sedimentconcentrations from the bottom of the watercolumn with enough “cleaner” water from higherin the water column) are performed to staywithin the required concentrations furtherdownstream. The Low Level Outlet (LLO)discharges highly concentrated water, theIntermediate Level Outlet (ILO) releases lessconcentrated flows and the High Level Outlet(HLO) discharges clear water (Figure 3). Theefficiency of such program is controlled with thebenefit of real-time sediment concentrationmonitoring implemented at the dam site and indownstream stations.

All other CNR hydropower facilities operateddownstream of the Génissiat dam are low headrun-of-the-river systems. For normal operating

initiated by dam operators in the upper SwissRhône and the French Rhône tributaries. At thesame time, it is crucial to keep the finesuspended sediment concentrationsdownstream of the dams low enough for severalriver uses, such as supporting aquatic life, andthe operation of intakes for cooling systems ofnuclear power plants, well-fields for drinkingwater supply and bathing areas. Moreover,floodwater routing must be ensured by guaran-teeing adequate hydraulic capacity of channelsand by avoiding adverse obstructions of damspillways, possibly resulting from sedimentdeposits. Good navigation conditions have alsoto be maintained through regular monitoringand maintenance of the riverbed. To deal withthese requirements, CNR has adopted anoverall sediment management program estab-lished under the supervision of the Frenchauthorities. Complementary to this masterplan,“environmentally friendly flushing” operationsare also regularly conducted at the Génissiatdam as a result of the historical transboundaryissues of the Rhône River.

“Environmentally friendly flushing”concept from the Génissiat DamSince the completion of the Verbois dam(located near Geneva, upstream of theGénissiat dam) in 1942, the Swiss operator SIGhas been initiating full drawdown flushingevents every three years to prevent increased-flood hazards that may be caused by sedimen-tation in the Verbois reservoir. Before 2016,Swiss reservoirs had used to be completelyemptied during these operations, leading tovery efficient remobilization rates but also tolethal effects on the aquatic fauna due tosuspended sediment concentrations reachingup 40 g/l.

On the contrary, the sediment releasedownstream of the Génissiat dam (104 m high,commissioned in 1948) has been conductedunder strict restrictions, especially since 1980as a result of a progressively increasing under-standing of sensitive issues on the FrenchRhône River. In particular, the suspendedsediment concentrations released from theGénissiat reservoir have not to exceed 5 g/l onaverage over the entire operation, 10 g/l onaverage over any 6 hours period, and 15 g/lover any 30 minutes period. Respecting thoselimits allows maintaining bearable life conditionsfor the aquatic fauna and preventing efficientlyadverse effects. To achieve this objective,routing and regulation of fine suspendedsediment concentrations discharged from the

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Figure 2. Typical CNR run-of-the-river facility

Figure 3. Management of the Génissiat reservoir during flushing sediment operations


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conditions, the reservoir water level upstream ofeach dam is more or less horizontal. Duringhigh flows or flood conditions, the spillwaygates are progressively opened to decrease thewater level upstream of the dam and to increasethe waterline slope throughout the reservoir.This situation avoids extra-flood hazards forriverine people and allows the recovery ofnatural-like flow conditions in the wholereservoir. The routing (or sluicing) of inflowingsediments throughout the reservoir is thus facili-tated and previously deposited sediments aremore easily remobilized. The sediment transportthrough CNR dams is also eased because thecrest of the spillway weir is practically at thesame elevation as the river bottom prior to damconstruction and because the heights of thespillway gate and dam are very similar.

Lessons learnedThe efficiency of such a gate arrangement andthe operation rules associated with its configu-ration has been demonstrated for decades andmakes possible the sustainable management ofsediment fluxes with a very limited impact onthe aquatic life and river users. Since thebeginning of 1990’s, the operation rules havebeen continuously optimized. The annualsedimentation rate in the Génissiat reservoir hasbeen consequently reduced by half, and for the1993-2018 period, the yearly rate of sedimentspassing through the dam outlets has increasedup to 85% on the average, i.e. only 15% of theinflowing suspended sediment flux have beentrapped into the reservoir (Figure 4).

Additional gains are expected in the near termas Swiss and French operators have to complywith the same restrictions on suspended

sediment concentrations released from damssince 2016. This evolution results from acooperative work performed between 2012 and2016 by the operators and the regulatoryauthorities from both countries with theobjective of ensuring a consistent andsustainable management of sediment fluxesthroughout the whole river cascade. Thebenefits of this new operating scheme havebeen demonstrated during the 2016 event,allowing an adequate balance of the sedimentfluxes flowing to the Génissiat reservoir andfrom the dam outlets. The downstreamsediment transfer throughout the CNR run-of-river facilities has been also increased by 50%compared to previous events. Such operation ishowever costly to CNR, which engages a staffof 400 people 24 hours a day over approxi-mately 10 days, at a cost of about 6 to 8 millioneuros (based on the 2012 and 2016 flushing).With the benefit of such design and operationpatterns, the impact on sediment fluxes issignificantly minimized. Locally, some sedimentdeposits may, however, occur, especially inareas where the flow velocity is very low, such

as navigation lock garages, harbors, and theRhône-tributary confluence zones. In the LowerRhône River (downstream of the city of Lyon)the average volume of deposits in the riversystem represents 0.04% to 5% of the annualinflowing suspended sediment fluxes (Figure 4).These changes have been observed during thecontinuous monitoring of the river and hydraulicstructures performed by CNR with a fleet ofhydrographic boats. A comprehensive updateof the bathymetric state of the river is carriedout with a minimum frequency of 5 years orafter significant floods.

In order to keep adequate conditions fornavigation, dam operation and hydraulic safety,maintenance works are also performed onsediment deposits and vegetation in theframework of a management plan establishedunder the supervision of the French authorities.This plan is generally updated every 10 years.Ecological restoration works carried out by CNRon oxbows and alluvial margins represent alsoa noticeable part of these works. Consideringdredging operations only, which represent inrecent years an annual average volume of 0.54Mm3, the distribution of works relatively to theissues at stake is as follows: 41% for navigationsafety, 41% for ensuring flood passage, 13% fordam operation and 5% for biodiversityrestoration. For approximately a decade,extraction of sediment deposits in the channelhas ceased. These deposits are instead artifi-cially resuspended in the flow and reinjected inthe riverbed further downstream, consideringfine and coarse particles respectively. Thisrequirement minimizes the potential disruptionof sediment continuity down to the Rhône RiverDelta and contributes to prevent its erosion.The management scheme defined and imple-mented by CNR has demonstrated thatachieving a sustainable management ofsediment fluxes through hydropower cascadesis possible. This program requires that severalkey factors are respected, namely adequatedesign and positioning of dam outlets, devel-opment of an operation pattern of the reservoirallowing the progressive recovery of naturalflow conditions, regular monitoring of the riverchannel and hydraulic structures, and finallyadaptive management of the river dependingon a comparison of target states and observed

evolutions. n

References[1] Mathurin, J.L., Cote, M., Levasseur, L. (2015). CNR model, or how

to reconcile management, economic development andsustainable development of a large navigable river. ProceedingsI.S.RIVERS, Lyon, France.

[2] Savey, P. (1982). Integrated development of a large river: the Rhône- A. General design and effect on floods and subsurface waterlayers. La Houille Blanche, 5-6, 421-425

Christophe Peteuil is leading theCentre for the Behavioral Analysisof Hydraulic Structures (CACOH)of Compagnie Nationale du Rhône(CNR), France (www.cnr.tm.fr/en/). He formerly occupiedvarious positions at the TorrentialHazards Division of the French

Forestry Commission, Ministry of Environment. He is a senior hydraulic engineer with 20-years ofexperience. His areas of expertise are fluvial hydraulics,sediment transport monitoring and modelling, as well as reservoir sedimentation and torrential hazardsmitigation.

Figure 4. Sediment trapping rate at CNR reservoirs according to the residence time of water (reservoircapacity volume/mean annual river flow)


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Reharge reservoir dams in of oman:concept and roleThe Sultanate of Oman is an arid country wheredrought conditions prevail and water is precious(Figure 1). Oman experiences a severe watershortage that threatens the national plans fordevelopment in all sectors (e.g. agriculture,tourism, industry). Government agencies andresearch institutions have been activelyaddressing different ways of augmenting waterresources, mainly groundwater. Indeed, thewater demand in Oman is mostly covered bygroundwater withdrawal, supplying 87% of thedemand, particularly for domestic andagriculture purposes. However, the intensive useof groundwater has led to the lowering of watertables and saltwater intrusion. One of theprudent measures to mitigate these problems isenhancing groundwater recharge (artificialrecharge) by intercepting floodwaters (which areoften wasted in the sea or in the desert) afterrainfall events, storing them temporarily in reser-voirs and down gradient infiltrating this water into

the soil and aquifers (Figure 2).The water in thereservoirs is detained for about two weeks toavoid evaporation and health risks. Then thestored water is released slowly through culvertsto the recharge basin which is locateddownstream of the dam. The recharge damembankments are often made of soil, which ishighly permeable, with a low-permeability claycore as the main seepage-checkingcomponent.

Forty-six (46) recharge dams have beenconstructed on alluvial valley wadis between1970 and 2018 in Oman, with a total storagecapacity of 101 Mm3. While desalinationprovides a seemingly unlimited but costly watersupply, recharge dams provide a limited watersupply but relatively cheaply. Additional benefitsof recharge dams are flood protection anddeceleration or even reversing of seawaterintrusion into coastal aquifers by creatinggroundwater mounds and, correspondingly,excess seaward oriented hydraulic slopes in

these aquifers. Therefore, maintaining damefficiency is necessary to achieve the optimumuse of catchment-scale water resources.

Silting of reharge dams: problemsand management starategiesRecharge dams in Oman are experiencing theproblem of siltation, i.e. deposition of sediments

SILTING OF RECHARGE DAMS IN OMAN: PROBLEMS AND MANAGEMENT STRATEGIES BY ALI AL-MAKTOUMI

In the Sultanate of Oman, 155 dams have been constructed as of 2018 for different purposes: flood protection (3dams), recharge (46) and surface storage (106). Recharge reservoir dams are an effective measure to manageand augment water resources, especially groundwater aquifers, through making use of floodwater which is oftenlost to the sea and desert. These reservoir dams proved their efficiency, however (like elsewhere in the world)facing challenges that threaten their amenities. One of the most important issues to be countered is the silting ofdams (i.e. reservoir sedimentation). The concerned water authorities along with academia are devoting manyefforts to solve this problem.

Figure 1. Map of Oman. Muscat is the capital of Oman Figure 2. The concept of recharge dam reservoirs

Figure 3. Areal satellite image for the Al-Khoudrecharge reservoir (the whitish area indicates thedeposited silt) (Google earth). Al-Khoud dam isthe oldest and largest recharge dam in Oman(5,100 m long, 11 m high), commissioned in 1985with initial storage capacity of 11.6 Mm3.


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standing will provide the foundation for futuredecision making by the Ministry of RegionalMunicipalities and Water Resources and othergovernmental agencies as related to future damdesign and maintenance. Research has beendone to gain more insight into the kinetics offiltration, surface-subsurface water dynamics,evolution of infiltration fronts, in essentiallyheterogeneous porous media of reservoirbeds[1,3,4,5,6]. Analysis of the results revealedthat the soil in reservoir areas is rapidly evolvingbecause of intensive anthropogenic hydrologicimpacts caused by periodic ponding, infiltrationand desiccation. This results in complicated anddynamic heterogeneities as the more finesediments are translocated vertically into thesubsurface, altering therefore the hydrologicalproperties of the substrate material[1,5].

brought by runoff water (Figures 3 and 4). Thisadversely affects the storage capacity of thereservoirs along with other problems (e.g. damsafety, water quality). Over time, layers ofsediments from intercepted and detained watercurrents cover the entire reservoir area.Consequently, the water infiltration ratedecreases, water loss via evaporationincreases, and the reservoir volume is reduced.For example, about 3.4 Mm3 of sediments havebeen deposited in the Al-Khoud reservoir since1985[1]. Unfortunately, there is no detailed dataon the silting rates of Omani dams, but anumber of them have been recently equippedwith gauging sticks to assess the volume ofsedimentation. The use of low-cost multispectralsatellite data for mapping the silting of damshas also been promoted[2].

As a common practice, the deposited materiallayer is removed to increase water infiltrationand storage space of the reservoir, but this isnot always possible or feasible. Another solutionis building small check dams, or siltation pondsalong the flashflood pathways to intercept mostof the sediments within the catchment beforethey reach the reservoir. It is more practical andless costly to clean up the reservoirs of smalldams. The trapped sediments are removed andused in the oasis clusters or scattered on thebanks of the waterway.

Mechanical intervention (bulldozzing, drilling)greatly improves the ability of the reservoir areato act as a surface-to-subsurface hydrologicalsink. The responsible water authority in Omanexcavates and scraps out the depositedsediments from the dam-beds and utilizes themin agricultural practices, with a plan to use thesesediments also in the pottery and stonewareindustry. However, mechanical removal ofsediments remains costly (e.g. around US$250,000 for the Al-Khoud dam for basic cleaningof debris), it is tedious and requires recurringactions after each flood-deposition event. Moreimportantly, part of the deposited fine particles iscarried by water infiltrating vertically into theporous medium (Figure 5). Hence, the surfacescraping cannot remove the clogging particles,which have already migrated deep into theparent bed material (commonly a coarsealluvium). Fine particles gradually change thephysiochemical properties of the originalsubsurface porous medium. Understanding thebehavior and patterns of the percolating soilparticles and their effect on infiltration andaquifer recharge is of critical importance forbetter management strategies. This under-

Dr. Ali Al-Maktoumi is AssistantProfessor in arid zone hydrology,and the Assistant Dean forPostgraduate Studies andResearch for College ofAgricultural and Marine Sciences(https://www.squ.edu.om/agr/Departments/Soils-Water-and-

Agricultural-Engineering/Faculties/Dr-Ali-Al-Maktoumi),Sultan Qaboos University, Oman. His research focusesin recharge dam’s efficiency, groundwater, hydrology,seawater intrusion, aquifer storage and recovery, andnumerical modeling.

Along with the problem of the reduction in thereservoir storage capacity, the alteration of thesoil properties are found to significantly affectthe ponding time , and the infiltration patternswithin the reservoir area. This increases the

Figure 4. (a) Recharge dam in Oman after a flash flood, (b) Empty dam reservoir in Oman after long dryspell, (c) Satellite images of a number of recharge dams in North coastal line of Oman (left image), andAl-Khoud dam (right Image). Note: the whitish color in these images indicates the siltation patches.Excavations showed that the thickness of the deposited sediments exceeds 2-3 m.

a

c

b


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potential hazards of flooding in the areasadjacent and downstream of the dam throughover-spilling of ponded water. Zones locateddownstream of the dam, which are supposed toserve as recharge areas, receive pluses ofreservoir water both from the dam’s culvertsand the spillways. This water is still rich in finesuspended particles which, similarly to whathappens in the reservoir itself, in parttranslocate vertically into the subsurface,hydraulically impair it, i.e. adversely affect therecharge process. In addition, reduced infil-tration through the recharge area downstreamof the dam intensifies surface runoff and henceincreases the loss of valuable fresh waterresources to the sea or desert, jeopardizing anyurbanized areas in its flow path by flooding.

Reservoir sedimentation threatens the stabilityand safety of the dam due to hydro-ecologicalinterplay[7]. The slopes of the embankment aresupported with gabions (Figure 3a) that havelarge mesh openings, acting as corridors andhosting settled suspended soil particles aftereach reservoir filling. The gabion serves as amulch which reduces evaporation from the verywet shoulder and clay core of the dam. Finetextured materials are characterized by highwater-holding capacity that intercepts the ex-filtrating water[7], and hence serves as a supply

water source that supports the growth of lushvegetation, which thrives in the embankment. Avegetation strip has been observed on theslopes of the embankment of a recharge dam inOman that emerged after torrential rains andtemporary filling of the dam reservoir (Figure4a). The vegetation is interpreted as the footprintof temporary storage of water, which is a small-sized groundwater mound within the permeableshoulder of the embankment[7]. The responsiblegovernmental entity set a monitoring program touproot this vegetation from the dam wall andreinforce the core with a concrete wall to avoidpossible damage to the dam structure. n

References[1] Al-Saqri, S., Al-Maktoumi, A., Al-Ismaily, S., Kacimov, A., Al-Busaidi,

H. (2016). Hydropedology and soil evolution in explaining thehydrological properties of recharge dams in arid zone environ-ments. Arabian Journal of Geosciences, 9(1), 1-12.

[2] Rajendran, S. (2015). Mapping of Siltations of AlKhod Dam,Muscat, Sultanate of Oman Using Low-Cost Multispectral SatelliteData. International Science on Remote Sensing, 13(03), 705-709.

[3] Kacimov, A.R., Al-Ismaily, S., Al-Maktoumi, A. (2010). Green-Amptone-dimensional infiltration from a ponded surface into a heteroge-neous soil. J. Irrigation and Drainage Engineering, 136(1), 68-72.

[4] Al-Ismaily, S.S., Al-Maktoumi, A., Kacimov, A.R., Al-Saqri, S.M, Al-Busaidi, H.A., Al-Haddabi, M.H. (2013). A morphed block-crackpreferential sedimentation: A smart design and evolution in nature.Hydrological Sciences Journal, 58(8), 1779-1788.

[5] Faber, S., Al-Maktoumi, A., Kacimov, A., Al-Busaidi, H., Al-Ismaili,S., Al-Belushi, M. (2016). Migration and deposition of fine particlesin a porous filter and alluvial deposit: Laboratory experiments.Arabian Journal of Geosciences, 9(4), 1-13

[6] Prathapar, S.A.; Bawain, A. A. (2014). Impact of sedimentation ongroundwater recharge at Sahalanowt Dam, Salalah, Oman.Technical note. Water International, 39(3), 381-393.

[7] Kacimov, A.R., Brown, G. (2015). A transient phreatic surfacemound, evidenced by a strip of vegetation in an earth damshoulder: the Lembke-Youngs reductionist model revisited.Hydrological Sciences Journal, 60(2), 361-378.

Figure 5. (a) Soil Pedons of the Al-Khoud dam bed, about thirty (30) years after the dam commission, (b)a typical soil profile illustrating the sedimentation in Al-Khoud reservoir and the deep percolation of fineparticles into the original gravelly alluvium

management vis-à-vis several competing objec-tives for the use of these reservoirs. Technicaland economic barriers also exist, drivenprimarily by the engineering challenges andcosts of retrofitting existing dams with new infra-structure to flush or bypass sediment. For newand existing dams, sediment managementstrategies should be evaluated on the basis ofcost and efficiency rather than the continuingneed for dredging. Finally, several site condi-tions, such as road access or valley geometry,may impact the suitability of any given sedimentmanagement practice at a site. A systematicapproach for evaluating the social, economic,ecological, and engineering tradeoffs ofsediment management could facilitate thiscritical aspect of sustainable water resources.Ultimately, for many areas of the world charac-terized by high sediment yields, a suite ofsediment management practices may benecessary.

AcknowledgementsThis article is adapted in large measure fromparts of the paper “Sediment Management in

Taiwan’s Reservoirs and Barriers toImplementation” by Wang et al.[5], published inWater. The authors gratefully acknowledgeTaiwan Sugar Corporation, Taipower Company,and Water Resources Agency under the Ministryof Economic Affairs in Taipei, for providingimportant data used in this article. n

References[1] O’Connor, J.E., Duda, J.J., Grant, G.E. (2015). 1000 dams down

and counting. Science, 348, 496–497.[2] Annandale, G.W., Morris, G.L., Karki, P. (2016). Technical guidance

note: Extending the life of reservoirs - Sustainable sedimentmanagement for run-of-river hydropower and dams. World Bank:Washington, DC, USA.

[3] Dadson, S.J., Hovius, N., Chen, H., Dade, W.B. (2003). Linksbetween erosion, runoff variability and seismicity in the Taiwanorogen. Nature, 426, 648.

[4] Hwang, J.S. (1994). A study of the sustainable water resourcessystem in Taiwan considering the problems of reservoir desilting;River Works Planning Department, Water Conservancy Bureau,Taiwan Provincial Government: Taichung, Taiwan.

[5] Wang, H.W., Kondolf, G.M., Tullos, D., Kuo, W.C. (2018). SedimentManagement in Taiwan’s Reservoirs and Barriers toImplementation. Water, 10(8), 1034.

[6] Water Resources Agency (WRA). (2016). Desilting tunnel project ofShimen Reservoir (first stage) - the basic design report ofAmouping tunnel. Water Resources Agency, Taichung City,Taiwan.

[7] Water Resources Agency (WRA). (2011). Feasibility study ofDawanping desilting tunnel project in Shihmen Reservoirsummary report. Water Resources Agency, Taichung City, Taiwan.

[8] Water Resources Agency (WRA). (2014). Evaluation of morpho-logical effects in downstream river due to sediment venting andreplenishment from the Shihmen. Water Resources Agency,Taichung City, Taiwan.

[9] Water Resources Agency (WRA). (2012). Long-Term measurementof sediment transport and density current simulation in ShihmanReservoir (1/2). Water Resources Agency, Taichung City, Taiwan.

[10] Water Resources Agency (WRA). (2015). Long-term monitoring ofsediment transport in Shihmen Reservoir. Water Resources

Agency, Taichung City, Taiwan.[11] Water Resources Agency (WRA). (2014). Long-Term

measurement of sediment transport and density currentsimulation in Shihman Reservoir (2/2). Water Resources Agency,Taichung City, Taiwan.

[12] Water Resources Agency (WRA). (2015). Feasibility study ofAmouping desilting tunnel project for Shihman Reservoir -summary report. Water Resources Agency, Taichung City, Taiwan.

[13] Palmieri, A., Shah, F., Annandale, G.W., Dinar, A. (2003). ReservoirConservation-Economic and Engineering Evaluation ofAlternative Strategies for Managing Sedimentation in StorageReservoirs: The RESCON Approach. Vol. 1. The World Bank:Washington, DC, USA.

[14] Kondolf, G.M., Gao, Y., Annandale, G.W., Morris, G.L., Jiang, E.,Hotchkiss, R., Carling, P., Wu, B., Zhang, J., Peteuil, C., Wang, H-W., Yongtao, C., Fu, K., Guo, Q., Sumi, T., Wang, Z., Wei, Z., Wu,C., Yang, C.T. (2014). Sustainable sediment management inreservoirs and regulated rivers: experiences from five continents.Earth’s Future, doi: 10.1002/eft2 2013EF000184.http://onlineli-brary.wiley.com/doi/10.1002/2013EF000184/pdf.

[15] White, R. (2001). Evacuation of Sediments from Reservoirs;Thomas Telford Publishing: London, UK.

[16] Water Resources Agency (WRA). (2014) Maintaining asustainable Tsengwen Reservoir planning report. WaterResources Agency, Taichung City, Taiwan.

[17] Tullos, D., Wang, H.W. (2014). Morphological responses andsediment processes following a typhoon induced dam failure,Dahan River, Taiwan. Earth Surf. Process. Landf., 39, 245–258.

[18] United States Society on Dams (USSD). (2015). Guidelines forDam Decommissioning Projects; United States Society on Dams:Denver, CO, USA; ISBN 978-1-884575-71-6.

[19] Chung, C.-C., Lin, C.-P. (2011). High concentration suspendedsediment measurements using time domain reflectometry. J.Hydrol., 401, 134–144. doi:https://doi.org/10.1016/j.jhydrol.2011.02.016.

[20] Espa, P., Brignoli, M.L., Crosa, G., Gentili, G., Quadroni, S. (2016).Controlled sediment flushing at the Cancano Reservoir (ItalianAlps): management of the operation and downstream environ-mental impact. J. Environ. Manage., 182, 1–12.

[21] Kjelland, M.E., Woodley, C.M., Swannack, T.M., Smith, D.L.(2015). A review of the potential effects of suspended sedimenton fishes: potential dredging-related physiological, behavioral,and transgenerational implications. Environment Systems andDecisions. Springer Publishing, New York, NY, US; 35, pp. 334–350.

[22] Servizi, J.A., Martens, D.W. (1992). Sublethal responses of cohosalmon (Oncorhynchus kisutch) to suspended sediments. Can. J.Fish. Aquat. Sci., 49, 1389–1395.

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Project Characteristics The Paute River is in the southern EcuadorAndes. The river is a tributary of the SantiagoRiver, which is a tributary of the Amazon River(Figure 1). Paute - Cardenillo (installed capacityof 596 MW) is the fourth stage of the CompletePaute Hydropower Project that includes theMazar (170 MW), Daniel Palacios - Molino (1100MW) and Sopladora (487 MW) plants (Figure 2).

The double-curvature Paute-Cardenillo Dam islocated 23 km downstream from the DanielPalacios Dam (Figure 3). The reservoir is 2.98km long and the normal maximum water level is924 m above sea level (MASL). The studydrainage area is 275 km2 and the mean riverbedslope is 0.05 m/m (Figure 2). The bed material iscomposed of fine and coarse sediments. Theuse of a point counting method allowed charac-terizing the coarsest bed material (diameterslarger than 75 mm) (Figure 4). The estimatedtotal bed load is 1.75 Mm3/year and themaximum volume of the reservoir is 12.33 Mm3.

In order to prevent the accumulation ofsediment into the reservoir, the dam ownerproposes periodic discharges of bottom outletsor flushing[1]. These operations should transportsediment far downstream, avoiding the advanceof the delta from the tail of the reservoir.Reservoir sedimentation and flushing wereinvestigated using empirical formulations as wellas 1D, 2D and 3D numerical modelling.

Flow Resistance CoefficientsEstimation of the total resistance coefficientswas carried out according to grain size distri-bution, sediment transport capacity rate andmacro-roughness (e.g. cobbles, blocks)[2]

(Figure 5). The flow resistance due to grainroughness (i.e. skin friction) was estimated bymeans of ten different empirical formulas. For

each analyzed flow discharge, calculations werecarried out by adjusting the hydraulic character-istics of the river reach (mean section andslope) and the mean roughness coefficients. Toestimate the grain roughness, only formulaewhose values fall in the range of the mean value- one standard deviation of the Manningresistance coefficient of all formulas wereconsidered. The formulas that gave values outof this range were discarded. The process wasrepeated twice. It was observed that the meangrain roughness was between 0.045 and 0.038.Using measured water levels for flow dischargesof 136 m3/s, 540 m3/s and 820 m3/s, the flood-plain and the main channel resistance coeffi-cients were obtained through the calibration ofthe 1D HEC-RAS v4.1 code[3]. Figure 6 showsManning’s roughness coefficients for flow ratesof different return periods, considering theblockage increment due to macro roughness.

According to the feasibility study[1], theminimum flow discharge evacuated by thebottom outlet to achieve an efficient flushingshould be at least twice the annual mean flow(Qma = 136.3 m3/s). The dam owner adopted aconservatively high flow of 409 m3/s (» 3Qma) forthe design dimensions of the bottom outlet.

Reservoir Sedimentation The time required for sediment deposition (bedload and suspended load) to reach the height ofthe bottom outlets (elevation 827 MASL)operating at reservoir levels was numericallyinvestigated using the 1D HEC-RAS program[3].The input flows were the annual mean flow (Qma = 136.3 m3/s) equally distributed in thefirst 23.128 km and the annual mean flowdischarge of the Sopladora hydroelectric powerplant (Qma-sop = 209 m3/s). The Sopladoradischarge comes from two dams locatedupstream. Sediment transport was computed

SEDIMENTATION AND FLUSHINGIN A RESERVOIR – THE PAUTE -CARDENILLO DAM IN ECUADORBY LUIS G. CASTILLO AND JOSÉ M. CARRILLO

Flushing is one possible solution to mitigate the impact of reservoir impounding on the sediment balance acrossa river. It prevents the blockage of safety works (e.g. bottom outlets) and the excessive sediment entrainment in the water withdrawal structures (e.g. power waterways). This study is focused on the morphological changesexpected in the Paute River (Ecuador - South America) as a result of the future construction of the Paute -Cardenillo Dam.

using Meyer-Peter and Müller’s formulacorrected by Wong and Parker[4] or Yang’s[5]

formula. Figure 7 shows the initial and finalstates of the water surface and bed elevation. The suspended sediment concentration calcu-lated numerically with HEC-RAS at the inletsection of the reservoir was 0.258 kg/m3. Thisvalue takes into account the sediment transportfrom the upstream river and the annual meansediment concentration from the SopladoraHydroelectric Power Plant.

Table 1 shows the total volume of sedimentdeposited in the reservoir and the time requiredto reach the bottom outlets (827 MASL). Severalwater levels in the reservoir based on futureoperations at the dam were considered, e.g.,860 MASL which is the water level consideredto operate the bottom outlets, 920 MASL thepondered average water level, and 924 MASLthe normal upper storage level (Figure 8).Results show that the sedimentation volume inthe reservoir increases with the water level in thereservoir, and requires a longer time to reachthe bottom outlet elevation. Using the correctedMeyer-Peter and Müller formula, with the level ofthe reservoir being at 860 MASL, yields thelargest sedimentation volume (1.47 hm3) andthe smallest time to reach the level of thebottom outlets (3 months and 27 days).

Yang Corrected Meyer-Peter & Müller

Reservoir Required Sediment Required Sedimentelevation time (years) volume (hm3) time (years) volume (hm3)(MASL)860 0.35 0.65 0.32 1.47892 5.10 2.77 2.58 3.86918 12.90 6.07 8.80 7.34920 13.60 6.33 9.50 7.64924 14.80 6.62 10.90 8.97

Table 1. Sediment deposition volume in thereservoir and the time required to reach thebottom outlets. Results are presented for twosediment transport capacity formulas


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s Figure 2. Paute Hydropower Project: Mazar (170 MW), Daniel Palacios - Molino (1100 MW), Sopladora (487 MW) and Paute - Cardenillo (596 MW)

s Figure 1. Geographical situation of thePaute River (Ecuador - South America)

s Figure 3. Design of the Cardenillo Dam (maximumheight of 136 m)

s Figure 5. Macro-roughness in Paute River at theCardenillo Dam reach

s Figure 4. Sieve curves of coarse bed material near Cardenillo dam

s Figure 7. Bed and free surface profiles near the dam; the level of thebottom outlets is 827 MASL

Figure 8. Scheme of the dam, water levels andsediment delta in the initial condition of the flushing

s Figure 6. Manning resistance coefficients in the main channel and flood-plain according to the flow discharge

s


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Flushing SimulationsThe efficiency of the hydraulic flushing dependson the ratio between the storage volume of thereservoir and the annual amount of incomingrunoff. Annandale[6] indicates that flushing iseffective if this ratio is less than 0.02, whereasBasson and Rooseboom[7] raised this thresholdto 0.05. The Cardenillo Reservoir ratio is about0.003. Hence, an effective flushing process maybe expected.

2-D numerical runsThe flushing process was analyzed using the 2Ddepth-averaged, finite volume Iber v1.9program[8]. The sediment transport rate wascalculated by the corrected Meyer-Peter andMüller formula[4]. The evolution of the flushingover a continuous period of 72 h was studied,according to the operational rules at the Paute-Cardenillo Dam. The initial conditions for thesedimentation profile (the lower level of thebottom outlet) was 1.47 hm3 of sedimentdeposited in the reservoir. The suspendedsediment concentration at the inlet section was0.258 kg/m3. In accordance with the future damoperations, the initial water level at the reservoirwas set at 860 MASL. Figure 9 shows the timeevolution of bed elevation during the flushingoperation. After a flushing period of 72 hours,the sediment volume transported through the

bottom outlets is 1.77 hm3. This volume is due tothe regressive erosion of the delta of sediment(1.47 hm3) which is almost removed in itsentirety during the flushing operation, and to theerosion of prior deposits accumulated at thereservoir entry (due to the inlet suspended load)during the first times of flushing.

Figure 10 depicts the transversal profiles of thereservoir bottom before and after the flushingoperation. Lai and Shen[9] proposed a geomet-rical relationship calculating the flushing channelwidth (in m) as 11 to 12 times the square root ofthe bankfull discharge (in m3/s) inside theflushing channel. In the present study, the meanwidth of the flushing channel is 220 m, which isabout 11 times the square root of the flushingdischarge.

3-D numerical runsTwo-dimensional simulation might not properlysimulate the instabilities of the delta of sedimentthat could block the bottom outlets. A 3Dsimulation could clarify the uncertainly during thefirst steps of the flushing operation. The compu-tational fluid dynamics (CFD) simulations wereperformed with FLOW-3D v11.0 program[10]. Thecode solves the Navier - Stokes equationsdiscretized by a finite difference scheme. Thebed load transport was calculated using the

corrected Meyer-Peter and Müller formula[4]. Theclosure of the Navier-Stokes equations was theRe-Normalisation Group (RNG) k-epsilon turbu-lence model[11]. The study focused on the firstten hours. The initial profile of the sediment deltawas the deposition calculated by the 1D HEC-RAS code. As in the 2D simulation, the waterlevel in the reservoir was 860 MASL. Due to thehigh concentration of sediment passing throughthe bottom outlets, the variation of theroughness in the bottom outlets was

Dr. Luis G. Castillo is TitularProfessor and Director of CivilEngineering Department at theTechnical University of Cartagena,Spain. In more than thirty-yearcareer, he has worked in some ofthe principal engineeringcompanies of Spain. His research

interests are physical and numerical modeling, spillwaysand energy dissipators, hyperconcentrated flows, andcharacterization of semi-arid zones. He is a ScientificAssociated Editor of the "Iberoamerican Water Journal,RIBAGUA", published by Taylor & Francis, under thesupport of the IAHR.

Dr. José M. Carrillo is AssociateProfessor at the TechnicalUniversity of Cartagena, Spain.His research interests includephysical and numerical analysis,plunge pools, and flushingoperations. He is the Editor of the“Journal of Latin America Young

Professionals” and President of the “IAHR South EastSpain Young Professionals Network”.

s Figure 9. Bed profile evolution during the flushing period of 72 h s Figure 11. Comparison of the flushing operations simulated with 2Dand 3D codes

Figure 10. Sedimentdeposition before andafter a flushing periodof 72 hours. BF is theflushing channel width

s


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Principal conclusionsEmpirical formulas and 1D simulations are usedto estimate sedimentation in the reservoir. Two-dimensional simulations allow the analysis of aflushing operation in the reservoir. Three-dimen-sional simulations show details of the sedimenttransport through the bottom outlets, where theeffect of increasing the roughness due to thesediment transport through the bottom outletswas considered. The results demonstrate theutility of using and comparing different methodsto achieve adequate resolution in the calculationof sedimentation and flushing operations inreservoirs. Suspended fine sediments in thereservoir may result in certain cohesion of thedeposited sediments, which might influence theflushing procedure. Carrying out a flushingoperation every four months, the cohesion effectin increasing the shear stress can be avoided.

Designers must take into account the highdegrees of uncertainty inherent in sedimenttransport (numerical modeling and empiricalformulae). Sensitivity analysis must beperformed to prove the models are robust to

considered. The Nalluri and Kithsiri formula[12]

was used to estimate the hyperconcentratedflow resistance coefficient on rigid bed (bottomoutlets).

Figure 11 shows the volume of sediment flushedand the transient sediment transport during thefirst few hours of the flushing operation. There isa maximum of 117 m3/s of sediment for anassociated flow of 650 m3/s (volumetricsediment concentration of 0.180), at the initialtimes for the high roughness 3D simulation.Later, the sediment transport rate tends todecrease to values similar to those obtained withthe 2D model. The total volume of sedimentcalculated by FLOW-3D is higher than with theIber program. The 2D simulations consideredthat all the total volume of sediment (1.47 hm3)may be removed in 60 hours. Considering thatsediment transport would continue during theentire flushing operation, the 3D simulation withhigh roughness would require 54 hours toremove all the sediments. A more detailedanalysis is given by Castillo et al.[13].


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various inputs and not limited to only a singlescenario. n

References[1] Consorcio PCA. (2012). FASE B: Informe de factibilidad. Anexo 2.

Meteorología, Hidrología y Sedimentología, Quito, Ecuador (inSpanish).

[2] Palt, S. (2001). Sedimenttransporte im Himalaya-Karakorum undihre bedeutung für wasserkraftanlagen. Ph.D. thesis, Mitteilungendes Institutes für Wasserwirtschaft und Kulturtechnik derUniversität Karlsruhe (TH), Karlsruhe, Germany (in German).

[3] U.S. Army Corps of Engineers. (2010). HEC-RAS 4.1 hydraulicreference manual, Davis, CA.

[4] Wong, M., Parker, G. (2006). Reanalysis and correction of bedloadrelation of Meyer-Peter and Müller using their own database. J.Hydraul. Eng., 132(11), 1159-1168.

[5] Yang, C. T. (1984). Unit stream power equation for gravel. J.Hydraul. Div., 10.1061/(ASCE)0733.

[6] Annandale, G. W. (1987). Reservoir sedimentation, ElsevierScience, Amsterdam, Netherlands.

[7] Basson, G. R., Rooseboom, A. (1996). Sediment pass-throughoperations in reservoirs. Proc., Int. Conf. on ReservoirSedimentation, Fort Collins.

[8] Iberaula. (2013). Iber: Hydraulic reference manual.www.iberaula.es .

[9] Lai, J.S., Shen, H.W. (1996). Flushing sediment through reservoirs.J. Hydrau. Res., 34(2), 237-255.

[10] Flow Sciences. (2011). FLOW-3D users manual version 10.0,Santa Fe, NM.

[11] Yakhot, V., and Smith, L. M. (1992). The renormalisation group,the -expansion and derivation of turbulence models. J. Sci.Comput., 7(1), 35-61.

[12] Nalluri, C., Kithsiri, M. M. A. U. (1992). Extended data on sedimenttransport in rigid bed rectangular channels. J. Hydraul. Res., 30(6),851-856.

[13] Castillo, L.G, Carrillo, J.M., Álvarez, M.A. (2015). ComplementaryMethods for Determining the Sedimentation and Flushing in aReservoir. Journal of Hydraul. Eng., 141 (11). 1-10.

IAHR World Congress

38th IAHR World Congress1-6 September 2019 Panama City, Panamahttp://iahrworldcongress.org/

39th IAHR World Congress4-9 July 2021 Granada, Spain

IAHR Specialist Events

HydroSenSoft - 2nd International Symposiumand ExhibitionHydro-environment Sensors and SoftwareFebruary 26 – March 1, 2019 Madrid, Spainhttp://www.ifema.es/hydrosensoft_06/

VI Jornadas de Ingeniería del Agua22-25 October 2019 Toledo, Spainhttp://www.jia2019.es/

11th River, Coastal and EstuarineMorphodynamics Symposium (RCEM 2019)16-21 November 2019 Auckland, New Zealandwww.rcem2019.co.nz

14th International Conference onHydroinformatics (HIC 2020)June 2020 Mexico City, Mexicohttp://hic2020.org/index.html

30th IAHR Symposium on Hydraulic Machineryand SystemsDate to be confirmed Lausanne, SwitzerlandContact: Prof. Francois Avellan

8th International Conference on PhysicalModelling in Coastal Science and Engineering(CoastLab 2020)25-29 May 2020 Zhoushan, China

25th IAHR International Symposium on Ice14-18 June 2020 Trondheim, Norway

10th International Conference on FluvialHydraulics (River Flow 2020)7-10 July 2020. Delft, Netherlandswww.riverflow2020.nl

International Conference on the Status andFuture of the World's Large Rivers (World’sLarge Rivers Conference 2020)10-13 August 2020. Moscow, Russian Federationhttp://worldslargerivers.boku.ac.at/wlr/

8th International Conference on FloodManagement (ICFM 2020)17-19 August 2020. Iowa City, Iowa, U.S.A.

15th International Conference on UrbanDrainage (ICUD 2020)6-11 September 2020. Melbourne, Australiahttp://www.icud2020.org/

IX Symposium on Environmental Hydraulics in Seoul Korea18-22 July 2021. Seoul, Korea

9th International Symposium on StratifiedFlows (ISSF 2021)30 August- 2 September 2021 Cambridge, UnitedKingdom

IAHR Regional Division Congresses

6th IAHR Europe Congress "Hydro-environment Research and Engineering - No Frames, No Borders"June 30- July 2 2020Warsaw, Polandhttp://iahr2020.syskonf.pl/

22nd Congress of the Asian Pacific Division of IAHR2020. Sapporo, Japanhttp://iahr-apd2020.eng.hokudai.ac.jp/

XXVIII LAD Congress 2020MéxicoContact: [email protected]


BackgroundOver the past several years the Mekong RiverBasin has experienced rapid development ofnew hydropower dams. Eleven (11) proposeddams on the main-stem of the Lower MekongRiver (six are wholly within the Lao People’sDemocratic Republic (Lao PDR), two are on theLao PDR-Thailand shared border, one on theLao PDR-Cambodia border, and two are whollywithin Cambodia), and numerous additionaldams on tributaries, have the potential to signif-icantly reduce the sediment input to thedownstream channel (Figure 1). The sedimentcontinuity in the Mekong basin is vital tomaintaining the fisheries that over 50 millionresidents rely on according to NationalGeographic. There is an increased need tounderstand and minimize the impacts ofreservoir sedimentation.

In 2013, the Government of Lao PDRrequested, through the U.S. Embassy inVientiane, specific assistance in hydraulic andsediment transport modeling for several keydam projects. Since 2014, reservoir sedimen-tation experts from the U.S. Army Corps ofEngineers (USACE) have interfaced in a seriesof technical exchanges with the Ministry ofEnergy and Mines Department of Energy Policyand Planning (MEM-DEPP). The overall goal ofthese exchanges is to equip MEM with thetechnical oversight and review skills to improvethe environmental and social sustainability ofhydropower development in the Mekong RiverBasin. Proper planning and oversight can limitthe impacts of dam building on the aquaticecosystem of the lower Mekong River andincrease the long-term sustainability of allreservoir benefits, including hydropower damsin Lao PDR.

Sediment Properties and TransportAnalysis WorkshopsSince 2014, USACE experts have held severalworkshops on topics such as sedimentproperties, river geomorphology, watershed

BUILDING RESERVOIR SEDIMENTMODELING CAPABILITIES WITH THE LAO PDR MINISTRY OFENERGY AND MINESBY JOHN SHELLEY, PAUL BOYD, STANFORD GIBSON, DANIEL PRIDAL AND TRAVIS DAHL

management, and dam safety considerations.A set of three workshops in 2015 in LuangPrabang, Paksan, and Pakse, introduced nearly80 MEM-DEPP engineers and technical staff tothe physical processes that transport anddeposit sediment in reservoirs, and methods toestimate the volume of sediment that has orwould deposit in a reservoir (Figures 2 and 3). In 2016, a subsequent pair of workshops intro-

duced river and reservoir sedimentmanagement methods as well as an initialexposure to sediment transport numericalmodeling.

Collaborative Numerical ModelingWorkshopsIn 2017, USACE personnel held a hands-onreservoir sediment modeling workshop with

Figure 1. Excerpt from “Existing and Planned Hydropower Projects in Lao PDR”[2]

Figure 2. Dr. Paul Boyd and Mr. Daniel Pridal with MEM-DEPP engineers at Nam Khan 3 dam site


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MEM-DEPP engineers. The workshop includedpresentations by USACE experts interspersedwith hands-on collaborative modeling exercisesconducted jointly by USACE and Lao PDRengineers. These modeling exercises utilizedthe Hydrologic Engineering Center RiverAnalysis System (HEC-RAS) version 5.0.3[1],which combines hydraulic modeling, sedimentmodeling, and reservoir gate operations. During

the workshop, MEM-DEPP engineers builtmodels using data from Lao watersheds andexisting or proposed dams. These models allowfor evaluating changes in management andinfrastructure, and how those can affect theprojected reservoir sedimentation. MEM-DEPPengineers modeled changes in reservoir poollevel management that resulted in increasedsediment transport to the river below the dams.Also tested was the effectiveness of drawdownflushing with and without low-level outlets. Overtime these actions can reduce the environ-mental impact of dams on the downstreamchannel and prolong the useful life of the damsand hydropower infrastructure.The workshop also included a visit to the NamMang 1 dam (Figure 4). The originalconstruction of the dam included a sedimentbypass tunnel. In most years, the heavily-forested watershed does not contribute signif-icant quantities of sediment. However, wildfires,

landslides, major storms, and other distur-bances have the potential to introduce signif-icant quantities of sediment in a short timeframe. The inclusion of the sediment bypasstunnel allows flexibility in future operations tohandle these eventualities. Not all current designs for dams include activesediment management infrastructure. MEMintends to use the sediment modeling skillset toensure that the current and future designs meetthe sustainability goals that the Government ofLao PDR has set forth for hydropower devel-opment.

FutureUSACE is continually expanding the sustainablereservoir management knowledge base, and willhold future workshops with MEM under a train-the-trainer framework. In the future, MEM-DEPPengineers who have developed the sedimentmodeling skillset will partner in deliveringworkshops to a larger group of MEM engineers,ensuring that knowledge effectively transfers toMEM staff located in provincial offices. Futureworkshops will use HEC-RAS v.5.0.5, which willbring increased geospatial functionality andindependence without the need for integrationwith licensed software.

This ongoing effort is supported by the UnitedStates Agency for International Development(USAID) through the Smart Infrastructure for theMekong (SIM) program, and the USACE. TheSIM program is a collaborative effort supportedby an inter-agency agreement between USAIDand the US Department of the Interior.

AcknowledgementsThe USACE technical team and authors wouldlike to express their gratitude to the leadershipwithin the MEM for their continued engagementand efforts to increase sustainability within theirhydropower development program. Specifically,Dr. Daovong PHONEKEO, Permanent SecretaryMEM, Mr. Khamso KOUPHOKHAM, ActingDirector General DL-MEM, and Mr.Vithounlabandid THOUMMABOUT, DeputyDirector General DEPP-MEM, have assisted inengaging MEM engineers, coordinatingengagements, and providing resources for thiseffort. n

References[1] Brunner, G.W. (2016). HEC-RAS, River Analysis System Hydraulic

Reference Manual. U.S. Army Corps of Engineers, Davis, CA.[2] MRC Planning Atlas of the Mower Mekong River Basin. (2011).

www.mrcmekong.org/assets/Publications/basin-reports/BDP-Atlas-Final-2011.pdf.

Dr. John Shelley is a hydraulicengineer and sedimentationspecialist for U.S. Army Corps ofEngineers, Kansas City District,River Engineering and RestorationSection, where he specializes insedimentation analysis andmodeling for rivers and reservoirs.

Dr. Shelley received his BS degree in Civil Engineeringfrom Brigham Young University and his Ph.D. in CivilEngineering from the University of Kansas.

Figure 3. Mr. Vithounlabandid THOUMMABOUT leads a team of MEM-DEPP engineers learning toestimate bed material size with a gravelometer (March 2015)

Figure 4. Nam Mang 1 Outlet Channel and Sediment Bypass Tunnel


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Nominating Committee 2019At its meeting in Lyon, France, in September 2018 the IAHR Council hasidentified a Nominating Committee (NC 2019) for the next Council electionahead of the next World Congress in Panama, 1-6 September 2019. TheNominating Committee will be chaired by Roger Falconer (UK), formerPresident of IAHR, and comprises Julio Kuroiwa (Peru), Ana Maria daSilva (Canada), Arthur Mynett (The Netherlands), Jose M. Carrillo (Spain),Angelos Findikakis (USA), Yoshiaki Kuriyama (Japan) and FarhardYazdandoost (Iran). IAHR President Peter Goodwin (USA) will serve as theCouncil contact person.

The NC collects proposals from individual and institutemembers, searches itself for candidates, andevaluates the performance of present Councilmembers in view of their possible re-election. Itmust consider the alignment of candidates withCouncil composition requirements, including thequestion of progression of Council Members toVice Presidential positions or to the Presidency.

It is the task of the NC to propose a list of candidatesfor the 2019 Council election, which includes ExecutiveCommittee positions (President, 3 Vice-Presidents andSecretary General) and regularly elected Council members. This listmust reflect a balance between the possibly conflicting requirements of:• world-wide representation of the IAHR membership and yet at the sametime a small active group which is capable to lead the Association, andto fulfil Council assignments;

• continuous renewal through new members while assuring necessarycontinuity;

• adequate representation of hydro-environment engineering practice;• IAHR’s goal to increase gender diversity in its leadership team – particularly for the future

Invitation to the membership for nomination of candidatesThe Nominating Committee hereby invites all IAHR members to submitsuggestions regarding nomination of possible candidates for Council.Please make your suggestions of potential Council candidates to anymember of the NC 2019 before January 31st, including a rationale for the suitability of the candidate proposed and an indication of thenominee’s willingness to accept if elected. The Nominating Committeewill give due consideration to all suggestions for Council Members.

NC 2019 slate of candidatesThe Nominating Committee will evaluate all proposed nominations forCouncil Members with respect to their qualification for fulfilling the majortasks of the IAHR Council.

The IAHR Council has the task to promote the interests of the Associationand co-ordinate the activities of its members serving the interests andneeds of Hydro-environment Engineering and Research, both at globaland at regional scale.

This includes long-range planning for the biennial World Congresses aswell as co-ordination and interlinkage of activities of Regional andTechnical Divisions and Committees, e.g. conferences, IAHR publicationsand Awards and promotion of continuing education, student chapters andshort courses. Membership promotion, finances, IAHR secretariat liaisonand links with institute members, industry and the profession are alsoimportant tasks, as well as relations with government agencies and otherprofessional/technical societies and international organisations.

The Nominating Committee will develop a slate of candi-dates, which must be published according to the By-Laws by March 1st. This slate may contain up to twocandidates for each position.

Any member wishing to receive a printed list of theslate of candidates should contact the Secretariatafter this date.

Nomination by petitionIf the Nominating Committee has not included your

suggestion in its slate or if you have another suitablecandidate not hitherto considered, all members have the

option to file a nomination by petition within two months after publi-cation of the NC 2019 slate. The new election procedure gives any groupof members in the Association, which feels that its interests are notproperly taken into account by the NC 2019 slate, the chance to submitnominations by petition for any of the regular Council member positions. Avalid petition requires signatures of 15 members from at least fivecountries or from a group of countries representing 10% of the IAHRmembership. This assures that there is support for a candidate whichgoes beyond a personal or national interest. All valid nominations bypetition will be included in the ballot.

Nominations by Petition must be submitted to the Secretariat within twomonths after publication of the NC slate of candidates with a statementfrom the candidate, that she or he is willing to accept the nomination, aresumé including professional career, involvement in IAHR, and astatement on the planned contribution as Council member.

BallotThe NC will submit its list of candidates to the Secretariat for publicationtogether with any candidates “by Petition”, reaching members at least twomonths prior to the congress. Members will be invited to elect the newCouncil through written or electronic ballot before and at the PanamaCongress, closing on Wednesday 4th September, 2019.

Contact:NC 2019 Chair:Prof. Roger A. Falconer, Former IAHR [email protected]

COUNCIL ELECTION 2019 – 2021

IAHR COUNCIL ELECTION

The Founding Statement and the Rules forAdministration of the Award are as follows:

Founding StatementThe Ippen Award was established by the IAHRCouncil in 1977 to memorialise Professor Ippen,IAHR President (1959-1963), IAHR HonoraryMember (1963-1974), and for many decades aninspirational leader in fluids research, hydraulicengineering, and international co-operation andunderstanding. The Award is made biennially byIAHR to one of its members who has demonstratedconspicuously outstanding ability, originality, andaccomplishment in basic hydraulic research and/orapplied hydraulic engineering, and who holdsgreat promise for continuation of a high level ofproductivity in this profession. The awards aremade at the biennial congresses of IAHR, wherethe most recent recipient delivers the ArthurThomas Ippen Lecture. The Award fund, which wasestablished by Professor Ippen's family, is autho-rised to receive contributions from associationmembers and friends of Professor Ippen. The 2015Award was made to Qiuwen Chen, China.

Rules for the administration of theaward1. The Arthur Thomas Ippen Award (hereinafterreferred to as the Award) will be made biennially, inodd-numbered years, to a member of IAHR whohas developed a conspicuously outstandingrecord of accomplishment as demonstrated by hisresearch, publications and/or conception anddesign of significant engineering hydraulic works;and who holds great promise for a continuing levelof productivity in the field of basic hydraulicresearch and/or applied hydraulic engineering.

2. Candidates must be under 45 years of age at thetime of presentation of the Award in the Congress3. Each awardee will be selected by the IAHRCouncil from a list of not more than three nomineessubmitted to the Council by a Committee (hereinafterreferred to as the Awards Committee) composed ofthe Technical Division Secretaries and chaired byIAHR Vice President, Prof. Silke Wieprecht. TheAwards Committee will actively seek nominations ofawardees from the IAHR membership, and willpublish at least annually in the IAHR Newsletter anadvertisement, calling for nominations. The adver-tisement will include a brief description of the supportmaterial which is to accompany nominations.4. The awardee for each year will be selected by theCouncil by mail ballot in January of the year of theCongress.5. The award need not be made during anybiennium in which the Council considers none of thenominees to be of sufficient high quality.6. The awardee will present a lecture, to be known asthe Ippen Lecture (hereinafter referred to as theLecture), at the IAHR World Congress following hiselection. The subject of the Lecture will be agreedupon by the awardee and the IAHR President. TheLecture will be published in the CongressProceedings. Public presentation of the Award will bemade by the President during the openingceremonies of the Congress.7. The awardee will be given a suitable certificatewhich will state the purpose of the Award andindicate the specific contribution(s) of area(s) ofendeavour for which the awardee is recognised. Theawardee also will receive a monetary honorariumupon presentation of the Lecture. The terms of thehonorarium will be published in the announcementof each biennial Award. The monetary honorarium

21st Arthur Thomas Ippen Award For outstanding accomplishment in hydraulic engineering and research

for the Award is US$1,500.8.Wide distribution of awardees among differentcountries and different areas of specialisation is tobe sought by the Award Committee and by theCouncil.9. No individual shall receive the Award more thanonce.

Previous WinnersQ. Chen, China (2017) in recognition ofoutstanding contributions in the field of environ-mental hydroinformatics and ecohydraulics.D. Violeau, France (2015) for outstanding contribu-tions in the field of fluid mechanics with specialemphasis on turbulence modeling for addressingcomplex, real-life hydraulics problems.G. Constantinescu, USA (2013) for outstandingcontributions in the field of fluid mechanics andespecially of turbulence modeling with applicationsto fluvial hydraulics and stratified flows.X. Sanchez-Vila, Spain (2011) for his outstandingcontributions in the field of groundwater flow andcontaminant transport with application to flowmodeling in heterogeneous porous media.Y. Niño, Chile (2009) for his outstanding basiccontributions in fluid mechanics with applicationsto sediment transport and environmental flowprocesses.M. S. Ghidaoui, HK China (2007) for hisoutstanding contribution to research in environ-mental fluid mechanics.A. M. Da Silva, Canada (2005) for her outstandingcontributions in the area of fluvial processes and inparticular, sediment transport.

IAHR AWARDS CALL FOR NOMINATIONS 2019


IAHR members are invited to submit nominations for the Arthur Thomas Ippen Award, Harold Jan SchoemakerAward, and M. Selim Yalin Award. These awards will be presented at the 38th IAHR World Congress, Panama,September 1-6 2019.

IAHR Vice President Prof. Silke Wieprecht is co-ordinating nominationsreceived for the 2019 Awards. The nominations should consist of aconcise statement of the qualifications of the nominee, a listing ofhis/her outstanding accomplishments, pertinent biographical data, anda proposed statement of the endeavours for which the nominatedawardee would be recognised. Each nomination should not be morethan two typewritten pages in length.

IAHR is interested to increase the visibility of particularly qualified femaleresearchers. Thus, we would appreciate efforts to identify qualifiedwomen. IAHR also attaches great importance to representing acomplete cross-section of the regional distribution and subject area ofits members. However, the scientific qualification is of primary impor-tance for the awarding of the prize. Although, a balanced considerationof the diversity of our members is very important to us.

Nominations for the three awards must be sent by January 31st, 2019 using the standard nomination form atwww.iahr.org / About IAHR / Awards

IAHR


IAHR members are invited to submit candidates fornomination for the M.Selim Yalin Award. This Awardwill be made for the 6th time at the 37th IAHR WorldCongress. The Founding Statement and the Rulesfor Administration of the Award are as follows:

Founding StatementThe M. Selim Yalin Award was established by theIAHR Council in 2006 to honour the memory ofProfessor M. Selim Yalin, Honorary Member (1925-2007), and Fluvial Hydraulics Section Chairman(1986-1991). Professor Yalin is remembered for hisprolific and pioneering research contributions influvial hydraulics and sediment transport, and for hisinspirational mentoring of students and youngresearchers.

The Award is made biennially by IAHR to one of itsmembers whose experimental, theoretical ornumerical research has resulted in significant andenduring contributions to the understanding of thephysics of phenomena and/or processes inhydraulic science or engineering and who demon-strated outstanding skills in graduate teaching andsupervision. The awards consisting of a certificateand cash prize are presented during the IAHR WorldCongresses. The Award fund, which was estab-lished by the family and friends of Professor Yalin, isauthorised to receive contributions from associationmembers and friends of Professor Yalin.

Rules for the administration of theaward1. The IAHR M. Selim Yalin Award (hereinafterreferred to as the Award) will be made biennially, inodd-numbered years, to a member of IAHR whose

7th M. Selim Yalin Award for significant and enduring contributions to the understanding of the physics of phenomena and/or processes in hydraulic science

or engineering, and demonstrated outstanding skills in graduate teaching and supervision

experimental, theoretical or numerical research hasresulted in significant and enduring contributions to theunderstanding of the physics of phenomena and/orprocesses in hydraulic science or engineering and whohas demonstrated outstanding skills in graduateteaching and supervision.2. Each awardee will be selected by the IAHR Councilfrom a list of not more than three nominees submitted tothe Council by a Committee (hereinafter referred to asthe Award Committee) composed of the TechnicalDivision Secretaries and Chaired by a Council Member.The Award Committee will actively seek nomination ofawardees from the IAHR membership, and will publishat least annually in the IAHR Newsletter an adver-tisement, calling for nominations. The advertisement willinclude a brief description of the support material whichis to accompany nominations.3. The awardee for each biennium will be selected bythe Council either at its meeting during the precedingeven-numbered year or by mail ballot in January of theyear of the Congress.4. The award need not be made during any biennium inwhich the Council considers none of the nominees to beof sufficient high quality.5. Public presentation of the Award will be made by thePresident during a public ceremony taking place withinthe Congress.6. The awardee will be given a suitable certificate whichwill state the purpose of the Award and indicate thespecific contribution(s) of area(s) of endeavour for whichthe awardee is recognised. The awardee also will receivea monetary honorarium, the terms of which will bepublished in the announcement of each biennial Award. 7.Wide distribution of awardees among different areasof specialisation is to be sought by the AwardCommittee and by the Council. Efforts will also be made

to ensure a wide geographical distribution.8. No individual shall receive the Award more thanonce.

Previous WinnersM. H. García, USA (2017), in recognition ofoutstanding contributions in the field of numericalmorphodynamics and specially in the excellence ofhis teaching and mentorship of young professionalsas well as contribution to applied projects.A. Armanini, Italy (2015), for enduring theoretical,experimental and modeling contributions to theunderstanding of sediment and debris transportprocesses and excellence in graduate teaching andadvancement of academic programs in hydraulicengineering.Y. Shimizu, Japan (2013), for outstanding scienceand excellence in teaching and mentorship of youngprofessionals as well as contribution to appliedprojects.Prof. Ian Wood (2011), for outstanding contributionsin the field of hydraulic engineering and especially inthe experimental research of hydraulic structures, aswell as in the teaching and supervision of graduatestudents from around the world.I.Nezu, Japan (2009), for his outstanding researchcontributuions in both fundamental hydroscience (inparticular for his pioneering work in turbulanecemeasurements and analysis) and applied hydraulicengineering, and for his dedication to teaching andyoung professional mentoringG. Parker, USA (2007) for his outstanding achievements over thirty years inthe field of sediment transport, river engineering,river morphodynamics and submarine sedimen-tation processes

IAHR members are invited to submit candidates fornomination for the Harold Jan Schoemaker Award.This Award will be made for the 21st time at the 38thIAHR World Congress to the author(s) of the paperjudged the most outstanding paper published in theIAHR Journal of Hydraulic Research in the issues,starting with Volume 54 (2016) no. 5 up to andincluding Vol. 56 (2018) no. 4. A proposal fornomination shall be completed with a clearargumentation (maximum one page) regarding itsoutstanding quality and why the paper is of such aspecific quality that it outweighs the other papers ofthe considered series.

Founding StatementThe Schoemaker Award was established by theIAHR Council in 1980 to recognise the efforts madeby Professor Schoemaker, Secretary (1960-1979), inguiding the Journal of Hydraulic Research in itsformative years. The Award is made biennially by theIAHR to the author(s) of the paper judged the mostoutstanding paper published in the IAHR Journal.

Rules for the administration of theAward1. The Harold Jan Schoemaker Award (hereinafter

referred to as the Award) will be made at each biennialIAHR Congress, to the author(s) of the paper judgedthe most outstanding and published in the IAHRJournal during the preceding two-year period.2. The awardee will be selected by the IAHR Councilfrom a list of not more than three ranked nomineessubmitted to the Council by a Committee (hereinafterreferred to as the Award Committee) composed of theTechnical Division Secretaries and chaired by IAHR VicePresident Prof. Silke Wieprecht. The Award Committeewill actively seek nominations of awardees from theIAHR membership (also non-members whoseemployers are corporate members will be considered) 3. The awardee will be selected by the Council byballot. The awardee(s) shall be notified immediately bythe Executive Director.4. An award need not be made during any biennium inwhich the Council considers none of the nominees tobe of sufficient high quality.5. The award will consist of a bronze medal and acertificate.

Previous WinnersB. Vowinckel, et al for the paper “Entrainment of singleparticles in a turbulent open-channel flow: a numericalstudy” (Vol. 54, 2016, Nº 2)

T. Stoesser (2015) for the paper “Large-eddysimulation in hydraulics: Quo Vadis?” (Vol. 52, 2014,Nº 4)V. Heller (2013) for the paper “Scale effects inphysical hydraulic engineering models” (Vol. 49,2011, Nº 3)H. Nepf (2013) for the paper “Hydrodynamics ofvegetated channels” (Vol. 50, 2012, Nº 3)U. Chandra Kothyari, H. Hashimoto and K. Hayashi(2011) for the paper “Effect of tall vegetation onsediment transport by channel flows” (Vol. 47, 2009,Nº 6)H. Morvan, D.W.Knight, N.Wright, X.Tang (2009) forthe paper “The Concept of Roughness in fluvialhydraulics and its formulation in 1D, 2D, and 3Dnumerical simulation models” (Vol. 46, 2008, Nº 2) K.Blankaert and U.Lemmin (2007) for the paper“Means of noise reduction in acoustic turbulencemeasurements” (Vol. 44, 2006, Nº 1) E.J. Wannamaker and E.E. Adams (2007) for thepaper “Modelling descending carbon dioxide injec-tions in the ocean” (Vol. 44, 2006, Nº 3) A. Carrasco and C. A. Vionnet (2005) for the paper“Separation of Scales on a Broad Shallow TurbulentFlow” (Vol. 42, 2004, Nº 6)

21st Harold Jan Schoemaker Award for the most outstanding paper in the Journal of Hydraulic Research

reservoir · 2020. 5. 13. · (2) managing sediments within the reservoir through suitable dam...

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