leaky recharge dam--kahlown & abdullah

8/6/2019 Leaky Recharge Dam--KAHLOWN & Abdullah

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Pakistan Journal of Water Resources, Vol.8(2) July-December 2004/29

Leaky Dam to Rejuvenate Depleting Aquifersin Balochistan

M.A. Kahlown1

and M. Abdullah2

ABSTRACT: Groundwater is theonly dependable source in upland Balochistan. Its withdrawal has exceededthe recharge resulting in rapid declining of water tables. In order to restore it, a number of recharge methodshave been applied in the past including the construction of delay action dams. Whereas, in other parts of theworld resembling upland Balochistan topographic and hydro-geological conditions (Oman and other MiddleEast countries), the leaky dams are becoming popular as a sustainable recharging technique to rejuvenate the

depleting aquifers of such areas. Pakistan Council of Research in Water Resources (PCRWR) introduced andimplemented the concept of constructing and operating leaky dams in Balochistan under one of its researchand development projects. The first leaky dam was constructed during 2002 at Margat about 35 kilometres fromQuetta. A groundwater monitoring network consisting of 7 observation wells was installed to monitor effects ofthe dam. Watershed management measures in catchment area of the dam have included planting 600 shrubsof 3 Xerophytic species, i.e. Atriplex lentiformis, Atriplex Cansescens, and Salsola vermiculta. Groundwatermonitoring to evaluate the impact of leaky dam has been undertaken since its construction. Meanwhile theconcept has been appreciated and acknowledged by the people from all walks of life. Large scale adoption ofsuch techniques would improve aquifer recharge, agricultural economy, and living standards of people of theprovince.

KEYWORDS: Watershed, Groundwater recharge, Observation wells, Balochistan, Leaky dam, Depletingaquifers.

INTRODUCTION

Groundwater is the only reliable source offreshwater in Balochistan. Its use has increasedmany folds due to expansion of agriculture, rapidgrowth of population and industrialization duringthe last two decades. Consequently, theexcessive withdrawal from aquifers as comparedwith recharge has resulted in drying up of manydug wells, springs, and karezes (Kahlown andHamilton, 1994). The situation has been furtheraggravated by the recent extended drought(1998-2002) in the province. The winter andsummer rainfall during this drought has declinedby about 73 and 55% respectively of average

precipitation (Chaudhri et al., 2002). The scarcerainfall caused a drastic reduction of the surface

1Chairman, Pakistan Council of Research in Water

Resources, Khayaban-e-Johar, Adjacent Edhi Home, H-8/1,Islamabad. Ph: 92-51-9258959, Fax: 92-51-9258963, E-mail:[email protected], [email protected]

2Director, PCRWR, Water Resources Research Centre

(WRRC), Quetta, Pakistan.

drinking water resources, such as springs andkarezes and resulted in greater withdrawal bytubewells. This caused falling water tables in mostof the valleys. Consequently, the persistentdrought has imposed hardships on livestock andhuman settlements, and has reduced vegetativecover (Chaudhri and Hanjra, 2002).

WRECA (2000) indicates that the severestoverdrafts of groundwater extraction are occurringin the Pishin-Lora, the Gaj, the Zhob, the Nari,and the Dasht river basins. These basins needimmediate recharge measures to reverse thecatastrophic situation. The Pishin-Lora, the Zhoband the Nari basins fall in upland Balochistan

which is the major fruit growing belt of theprovince. The Pishin-Lora basins consisting of thedistricts of Quetta, Killa Abdullah, Pishin, Mastungand part of Kalat, form the main deficit area wheregroundwater abstraction far exceeds therecharge. WAPDA (1992) indicated the perannum water table decline rates in the basinwere from 0.23 to 1.17 m. Abdullah et al., (1999)


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M.A. Kahlown and M. Abdullah


reported that the recharge in the Pishin-Lorabasin was 5.80 m

3 /sec and abstraction was 7.25

m3/sec which indicates an overdraft of about 1.45

m

3

/sec from the aquifer. Sub-basin wise, Quettaand Pishin sub-basins are the areas wheregroundwater abstraction rates are alarmingly high.These sub-basins show a large deficit ingroundwater balance, as indicated by recedingwater tables. The Zhob basin consists of Zhoband Qila Saifullah districts. The Killa Saifullahsub-basin has previously been considered to be inthe groundwater surplus area, but due to thedrought and recent unprecedented construction oftubewells, this sub basin has also become adeficit area.

The main argument for conserving water in

underground aquifers rather than in surfacereservoirs is that underground storage is notsubject to the huge evaporation losses. There area number of options available for increasing thegroundwater recharge (Todd, 1980). InBalochistan and other parts of the world, therecharge techniques applied are delay actiondams; small, and mini check dams; ponds anddepressions; dugwell, inverted, and injectionwells; spurs and dikes; ridge-furrows, ditch-furrows, terraces, contour strips; diversions andzig-zag channels; surface spreading, ploughing,organic mulching and watershed management in

catchment areas by growing diversified andversatile plant species (Perkins and Birch, 1999).Williamson (1987) reported that a storm of 80 mmrain that fell on a catchment with vegetative coverproduced a lower peak runoff rate than that of a20 mm storm on a similar catchment with novegetative cover. He also predicted thatwatershed vegetation measures could add anaverage 33% more to the groundwater recharge.Khan and Chaudhry (1967) have proposed thatfor effective watershed management, theplantation must be coupled with appropriatemechanical structures for maximum recharge andminimum soil erosion.

In addition to above recharge measures, leakydams are becoming popular as a sustainablerecharge technique to rejuvenate the depletingaquifers of other areas resembling uplandBalochistan topographic hydro-geologicalconditions.

OBJECTIVES

(i) To construct, operate and evaluate leakydams for rejuvenation of depleting aquifer

and its social acceptability;(ii) To design and evaluate the field

hydrological monitoring network; and

(iii) To conduct benefit/cost ratio of leaky damsand to demonstrate the potential of leakydams for propagation and large scaleadoption in the areas where the techniqueis socially, economically and technicallyviable.

BRIEF HISTORY OF THE CONCEPT

Delay Action Dam

The Irrigation & Power Department, Governmentof Balochistan, is constructing Delay Action Damsparticularly in the hilly and mountainous steepuplands of Balochistan since 1960 with the aim toenhance the groundwater recharge forrejuvenation of depleted aquifers andrehabilitation of downstream karezes, springs,dug wells. The Department has constructed morethan 200 delay action dams in Balochistan. Indelay action dam groundwater recharge occursfrom the dam reservoir. These dams typicallyhave high initial recharge rates, which fall offdramatically with time due to clogging of

permeable capillary pores of the reservoir beds.Only 2 cm. silt layer can clog infiltration of water.In some cases the bed of delay action dams havesealed-up within one year of their construction.Later on most of the stored water losts throughevaporation, without contributing to the aquifer.

Leaky Dam

The construction of leaky dam in Balochistan is anew concept introduced by Mr. AyaduraiSomesan, WRECA Consultant of DevelopingCountries. Mr. Somesan had introduced theconcept of leaky dam by delivering a number of

presentations in the 3-days workshop titledStrategy Workshop on Water ResourcesManagement (Groundwater Depletion &Recharge) Quetta, Balochistan (July 13-15,2000), organized jointly by PCRWR, IUCN,Irrigation & Power Department and GeologicalSurvey of Pakistan.


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Leaky Dam to Rejuvenate Depleting Aquifers in Balochistan


The concept of Leaky Dam is to acceleraterecharge by releasing the water into down streamchannels of rivers and streams as soon as

possible after the silt has been settled in thereservoir. The design and construction of leakydam are on principles of leaky embankments andrelease of the silt free water to downstream areasfor infiltration, because the river & stream bedusually remains porous due to possessingvariable deep layers of mixed, boulders, cobbles,gravel, sand, silt and clay. Once, the runoff wateris made part of shallow to deep aquifer, itbecomes immune to evaporation losses andconserved for future use.

MATERIALS AND METHODS

Site SelectionA number of sites for construction of leaky damwere visited and surveyed around 50 km ofQuetta valley and the Margat site 35 km fromQuetta was found suitable. Because, the Margatvillage is located 1 km away from the dam site,which has been connected with carpeted road,public transport, telephone and electricity. Thepopulation (about 500 number) mostly belongs tofarming community and in spite of living undertribal system are docile and cooperative forfacilitating to launch Research & Development(R&D) activities without any interference and

monetary demands (common practice inBalochistan). The annual rainfall is in the range of150 to 200 mm under normal conditions. Theagricultural crops and orchards are grown throughpracticing the Khushkaba system (rainwaterharvesting & conservation) and no farmer hasinstalled any tubewell. There is only 1 spring(discharge less than 4 lps) located 3 km awayfrom the village and 1 dugwell (6 m deep); wateris being used only for drinking and domesticpurposes. There are a number of seasonalstreams and tributaries flowing in rainy seasonand feeding the main Degari stream flowing

parallel to Quetta-Degari road and ultimately fall inNari river near Sibi. The Irrigation Department,Government of Balochistan did not build anydelay action dam for groundwater recharge in thisarea. Hence, the site after conducting, the surveywas found appropriate and suitable for theconstruction of leaky dam due to narrow width(26 m) and gentle slope of the Margat stream.

Construction of Leaky Dams

The construction of the dam was initiated in April2002 and completed in October, 2002. Boulders

and G.I wire SWG-8 were used as the principalconstruction material. The construction of dambody was completed in three phases: (i)excavation of foundation; (ii) weaving of G.I. wireinto netting; and (iii) filling of boulders within thenets for building four steps of the dam. Upstreamand downstream aprons were made aftercompletion of main body of dam. Parallel pipingsystem on top of the 2

ndand the 4

thsteps was

provided to discharge surplus water from thereservoir. The stone pitching of stream banks andconstruction of cutoff as well as toe walls weremade to save the main dam body from erosion

process. Top of the dam acts as spillway. Generalfeatures of the dam are highlighted in leaky damupstream and downstream Table 1 and Figure 1(a & b).

Table 1: Salient Features of the Leaky Dam Project

Features Quantity

Catchment area (km2) 1.79

Storage capacity (m3) 11106

Height of dam above naturalsurface level (NSL) (m)

4.9

Steps of dam body (No.) 5

Cost (Rs. million) 1.6

Figure 1 (a): Upstream View of Leaky Dam


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Figure 1 (b): Downstream View of Leaky Dam

Establishment of Groundwater Monitoring

NetworkIn order to assess the effectiveness of leaky damin recharging the aquifer, a groundwatermonitoring network was established whichconsists of 7 observation wells. An observationwell is a simple tube or pipe inserted in the soiland used for measuring static groundwater level.The characteristics of the peizometers areindicated in Table 2. A typical cross-section of aobservation well is shown in Figure 2. PVC pipeshaving diameter of 50 mm and divided into blindand filter were inserted vertically into the boreholeto the 1 m below depth of water table.

The observation wells were installed from upstreamto downstream direction. The top of the dam wasused as the reference level for measurements of theelevations of the ground level at each observationwell. Water-table depths in the observation wellswere measured with water level indicator andsubtracted from the ground levels to obtain water-table depths with reference to the top of the leakydam. Figure 2: Typical Cross-Section of an Observation Well

Table 2: Details of Groundwater Monitoring Network

Foundation aboveGround Surface (m)

Piezometric Depth (m)Observation well Position

Distancefrom

Dam (m)

Elevation atGround Surface

(m) Blind Filter Total

PZ-1-Right Hand Side 335 42.80 0.61 10.67 4.57 15.24PZ-2-Left Hand Side 457 37.41 0.73 10.67 4.57 15.24

PZ-3-Left Hand Side 610 37.96 0.49 9.14 3.05 12.19

PZ-4-Right Hand Side 762 33.54 0.85 10.67 4.57 15.24

PZ-5-Right Hand Side 945 34.48 0.67 9.14 21.33 30.47

PZ-6-Left Hand Side 945 31.68 0.61 10.67 4.57 15.24

PZ-7-Left Hand Side 1067 24.83 0.61 10.67 4.57 15.24


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Aquifer Formation Characteristics

While drilling holes for installation of observationwells, lithologic samples were collected and plottedto the depth of each observation well. It was noted,at most observation well locations, that the upper 3m of the profile was a highly permeableconglomerate formation comprised gravel, sand,clay, pebbles, cobbles and therefore, wasconsidered favourable recharging lithology. Thelayer from 3 to 4.5 m was generally a mixture ofcoarse to fine texture materials in all observationwells except at PZ-6 where it is a semi rechargingformation. Hence, the recharging aquifer is shallowwhich provide free horizontal and verticalgroundwater transport system. The underlying stratagenerally below 4.5 m (and below 7.6 m at PZ-6) ismostly shale which is an impermeable formation andallows practically negligible recharge of water andconsequently tends to confine water in the morepermeable layers (Table 3). These shale materialsare unable to transmit significant quantities ofgroundwater to the nearby wells, springs, karezesetc., under ordinary hydraulic gradients.

Watershed Characteristics and ManagementPractices

After completion of the construction process ofleaky dam, the watershed management practiceswere initiated primarily through selection andtransplantation of xerophytic forage shrubs and

making of check dams in the catchment area. Theoverall conditions of the catchment area beforetransplantation of plant species are described:

Soils

The soils of leaky dam area are calcareous andderived from limestone, sandstones andsedimentary rocks. These soils have ahomogeneous, porous and coarse texture, have

low organic matter, fall under over grazed anderoded degraded arid lands. Topographically, theMargat area is classified into three categories i.e.

(i) the mountains and hills characterized by steepslopes, bare rocks and no soil cover subject towater erosion; (ii) the piedmonts have deep welldrained homogeneous, silty to fine silty loamysoils and gravelly fans and terraces excellent forinfiltration but possessing dense clay pans andshale below 15 to 20 m depth; (iii) the stream bedand valley are alluvial deposits consisting oflayers of clay, gravel, silt, sand or an admixture ofthese materials, well drained, medium to coarsetextured, have excellent potential for recharge andgood for growing plants under watershedmanagement, but possessing dense clay pans

and shale below 4 to 5 m depth.

Slope

The Margat leaky dam site and its catchment areacomprise mountain ranges, piedmont plains andalluvial fans occupying gentle to steep slopes.The rainfall events in this area are torrential type,on runoff converted into high velocity flash floods;the consequent run-off may be either lostunutilized through the main drainage system or apart may be percolated in the alluvial fans orpiedmont plains and ultimately reaching the mainor perched aquifers. However, the alluvial fans

having gentle slopes lie immediately next to thefoot of the mountains and comprised coarsematerial deposited by the hill torrents duringfloods, act as good recharge zones for aquifers.Whereas, the piedmont plains are present next tothe alluvial fans and aprons consisting of relativelyfiner to coarse materials brought by the torrents.The infiltration rates are slightly lower than thealluvial fans to recharge the aquifers.

Table 3: Depths of Materials in the Aquifer with Significant Water Transmissibility (m)

Rocks and Earth Material PZ-1 PZ-2 PZ-3 PZ-4 PZ-5 PZ-6 PZ-7Gravel Sand Clay, Pebbles &

Cobbles

0-3.0 0-3.0 0-3.0 0-3.0 0-3.0 0-4.5 0-3.0

Admixture 3-4.5 3-4.5 3-4.5 3-4.5 3-4.5 4.5-7.5 3-4.5

Shale (grayish/weathered material) 4.5-15 4.5-15 - 4.5-10.7 4.5-30 7.5-15 4.5-15Limestone - - 4.5-6 - - - -

Shazij Shale (Boulder, MixedClays, Shale, with Pebbles etc.

- - 6-30 - - - -

Total 15 15 30 15 30 15 15


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Vegetation

The Margat Leaky Dam catchment, tributaries and

stream bed and valley have native plant speciespossessing xerophytic characteristics with growthhabit of seasonal and perennial nature. Theconditions of low precipitation and even six yearsconsistent past drought, extreme lowtemperatures, high wind and evaporation, lowhumidity and degraded lands were remained verydifficult for survival of plant life, when there wereuncontrolled and over grazing, cutting anduprooting by the local communities. Thepersistent drought had caused irreparable lossesto land, water, vegetative cover as well aslivestock and caused extensive damage to the

range and feed resources which were providingup to 70% of the total feed requirement of 85%livestock (small ruminants) numbering about 159heads before construction of leaky dam.Uprooting of the range bushes, grasses and treesfor fuel wood and chopping of drought survivingplants species for livestock feeding has furtheraggravated the situation. In the area the nativespecies were identified viz. trees: Mulberry,Quetta Pine, Prosopis cineraria, P. juliflora,Tamarix articulata, T.aphylla, Ziziphus mauritiana;Shrubs: a number of species belonging toChenopodiaceae family, wild Tulip, Alfalfa &

Roses, Atriplex halimus, Suaeda fruticosa,S.maritime, Haloxylon recurvum and Hermal(local name); Grasses: Sacchrum Munja,Agropyron cristatum, Cynodon dactylon, Elymus

juncus, Panicum antidotale. After the constructionof leaky dam, the perennial forage xerophyticshrubs like Atriplex lentiformis, A.canescensandSalsola vermiculta L. have been transplantedunder the watershed programme.

The native plant species were preserved bycontrolling grazing and exotic species wereintroduced in the watershed management. Due tofrequent and prolonged droughts in Balochistan,the propagation of drought tolerant species isessential because it is not possible to irrigate theplantation regularly for their lifetime period in thecatchment area. Three shrub species possessingthe xerophytic and perennial characteristic wereselected and planted in the catchment of the leakydams during April 2003 (Figure 3 a & b).

Figure 3 (a): Native Vegetation in Catchment AfterControlled Grazing Practice

Figure 3 (b): Transplanted Xerophytic Exotic Shrubs inCatchment

RESULTS AND DISCUSSION

Immediately after the construction of leaky dam,monitoring of groundwater levels downstream ofdam, effect of catchment improvement practices,sedimentation in the reservoir and the retentiontime of water in the reservoir after each runoffevent was initiated. The results of this monitoringare discussed in detail as under:

Effectiveness of Leaky Dams

Leaky dams for recharging groundwater are anew concept in Balochistan. These dams aredesigned and constructed to increasegroundwater recharge by holding water until mostof the sediment has settled and allowing waterwith little sediment to flow through the damsslowly. The introduction of such dams iseconomically and technically viable in areas


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where construction material is easily available andseasonal streams are usually sufficientlypermeable for transmitting surface water to the

aquifer. In this way, the leaky dam could be agood substitute for traditionally used Delay ActionDams which are facing problems of deposition ofsilt and high evaporation. Leaky dams enablemore recharge to the aquifer where the water isnot subject to evaporation losses.

Structural Stability of Leaky Dams

The structural stability of dam body was foundstable and durable because the whole structurewas combed by making underground foundationand above surface 5 steps with increasing widthtowards foundation. The steps were constructedby netting the quality and compact boulders and

stones, having size of more than 200 mmdiameter, divided into crates and then assembledtogether into a network through steel wires. Theconstructing 1.5 m deep RCC cutoff and 2 m toewalls on upstream and downstream aprons,respectively ensured the stability. Moreover, torelease the unpredicted flood events, thedischarging pipes of 6 inches dia and top of thedam body acted as spillway have and ensured thestability against any damage (Table 4).

Operational Performance

The leaky dam was constructed 1st

of its kind in

Balochistan, under the concept of leaky

embankments for allowing more rainwaterrecharge in the main stream bed instead of damreservoir opposite to conventional storage type

delay action dams (DAD), previously built morethan 180 by the Irrigation Department,Government of Balochistan. The overallperformance was found satisfactory in respect ofincrease in groundwater levels due to recharge asevident from the record of the groundwater levelsin 7 observation wells installed downstream of theleaky dam (Figure 4) as well as its direct andindirect affects on overall improvement of crops,orchards, livestock and ultimate economicbenefits to the nearby village community.

Leaky and Check Dams

After construction of leaky dam, a series of 200small size check dams in the catchmenttributaries feeding the main Margat stream weremade to reduce the runoff velocity and silt load.Four large size check dams were made acrossthe Margat stream to create maximum retentiontime for water to recharge (Figure 4). Theimmediate downstream locations were used foralready installed injection wells. The effectivenessof such cheap and easily made check damswould be visible after a few normal rainy yearsand better establishment of transplanted plantspecies under watershed management practices.

Table 4: Structural Measurements of Leaky Dam

Steps Dimensions(Length x Width x Height) (m)

Crates (No.) Discharge Pipes (No.)

Foundation 25.9 x 5.8 x 1.2 5 -

Step 1 30.5 x 4.9 x 1.7 8 -

Step 2 33.6 x 4.1 x 0.9 73 (15.24 cm dia

GI with valve)

Step 3 36.6 x 3.3 x 0.9 7 -

Step 4 39.7 x 2.6 x 0.9 84 (15.24 cm dia

GI with valve)

Step 5 42.7 x 1.8 x 0.9 8 -

Apron Dimension(Length x Width x Height) (m)

Crates (No.)Cutoff/Toe Wall Dimension(Length x Depth x Width) (m)

Upstream 25.9 x 5.1 x 0.4 17 Cutoff Wall 25.9 x 1.5 x 0.3

Downstream 25.9 x 6.1 x 0.4 26 Toe Wall 25.9x 1.9 x 0.3


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Figure 4: Layout Plan of Leaky Dams and Groundwater Monitoring Network at Margat, Quetta-Pakistan


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Sedimentation and Rainwater Retention

The sedimentation is considered the most vital

factor in reducing the overall utility and life ofdams and others structures through decreasingstorage capacity as well as recharging potential ofthe reservoirs. The unconsolidated rocks andearth particles of catchment area i.e. looseconglomerate, sandstone, limestone, boulder,pebble, cobble, gravel, sand, silt, clay, and brokenstone alongwith vegetative matter and animal

manures once moved from the place of origin to anew place under the force of gravity, runoff waterand wind is called sedimentation. The Margat

leaky dam catchment was in degraded condition,due to lack of watershed management measures,over grazing, cutting and uprooting of trees,shrubs and grasses for fuel and forages andfrequent droughts. After each runoff event, thewater retention time and sedimentation data wasrecorded (Table 5).

Table 5: Rainfall, Reservoir Water Retention Time and Sedimentation Data

MonthRainfall(mm)

WaterRetentionTime

*(Hr)

ReservoirWater

Depth (cm)Sedimentation

**

(cm)Remarks

November-02 23.50 2 - 0.50 1st

rainfall after 6 years drought,maximum recharge occurred, sedimentsretained in the spaces between boulders& stones of dam body and reservoirapron.

December-02 32.20 3 15 1.00 Thin layer of sediments deposited infront of dam body and on reservoirapron. Nominal quantity of water passedthrough dam body and recharged thestreambed. No loss due to runoff.

January-03 23.20 6 25 1.00 Fine clay and silt sediments passedthrough dam body and deposited in frontof check dam made in the stream.

March-03 11.10 - - --

May-03 16.00 1 30 1.50 -

July-03 23.00 5 38 5.50 More sedimentation and water rechargein the reservoir as well as in the mainstream without any loss of water

November-03 26.00 7 25 6.50 More sedimentation and water rechargein the reservoir as well as in the mainstream without any loss of water.

January-04 64.40 24 76 12.50 More runoff alongwith maximumsedimentation in the dam reservoir andtwo check dams small reservoirs built inthe stream. Surplus runoff water entered

in main Degari stream.February-04

***26.70 10 30 3.00 -

Total 246.10 - - 31.50 -

*Retention time of water in the leaky dam reservoir after each runoff event.

**Sedimentation in the leaky dam reservoir after each runoff event.

***No rainfall recorded from March to October, 2004.


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Changes in Water-Table Depth

After completion of the leaky dam, the water-table

data was recorded. The first readings wererecorded in October, 2002 which was consideredas baseline. The data recorded during the monthsreflected the water-table depth due to the droughtperiod. The first rainfall of 23.5 mm was receivedin November, 2002. Subsequent rainfall eventsduring the year 2002-03 were so few and similarthat they did not produce groundwater rechargedue to the confined nature of this shallow aquifer.The movement of water was restricted and smallvariations in water-table fluctuations that havebeen demonstrated specifically in PZ-1 and PZ-2may be due to their proximity to the leaky dam

and the water ponded in front of it. Similar, butsmaller increases in height of the water table wererecorded in observation wells installed fartherdownstream from the leaky dam i.e. PZ-3 to PZ-7.The overall picture indicates rises of water table atobservation wells PZ-1 & PZ-2 followed by, PZ-5,PZ-6, PZ-7, PZ-4 and PZ-3 respectively; rangingfrom 6.3 m near the dam to more than 2.0 m atgreater distance. These increases generallyreflect the effectiveness of the leaky dam ingroundwater recharge. Additional detail of this risein the water table due to recharge in the area isshown in Figure 5. A more complete assessment

of leaky dam and other recharge measures will bepossible after collection of data for at least fiveyears, including at least two years of normalrainfall.

Role of Plantation in Watershed

A major feature of watershed managementpractices is the planting of appropriate plantspecies within the catchment, stream, tributariesand along reservoir in addition to preserving thenative vegetation through controlled grazing. Theplantation foliage reduces the rate and velocity ofrunoff by trapping and delaying the water,

associated reduction in the level of silt carried inthe flood flow, increases vegetative land coverand organic matter as well as provides forage,fuel wood and other usable materials. The rootsplay dominant role in enhancing recharge byincreasing infiltration through flocculation of earthand rock particles, opening the land bypenetrating the hard layers of consolidated rocks,

clayey hard pans and impermeable shale to formnew arteries and channels for transmitting the rain

and surface water to the groundwater aquifer.Williamson (1987) reported that a storm of 80 mmrain that fell on a catchment with vegetative coverproduced a lower peak runoff rate than that of a20 mm storm on a similar catchment with novegetative cover. He also predicted thatwatershed vegetation measures could add anaverage 33% more to the groundwater recharge.Khan and Chaudhry (1967) have proposed thatfor effective watershed management, theplantation must be coupled with appropriatemechanical structures for maximum recharge andminimum soil erosion.

The native plant species in the leaky damcatchment area are mostly seasonal possessinglow foliage and less canopy cover, hence, threeshrub species possessing the xerophytic,perennial, good foliage and deep rootingcharacteristics were selected and transplanted inthe catchment of the leaky dam during April 2003(Table 6). The propagation of drought tolerantspecies was essential because it was not possibleto irrigate the plantation regularly for their lifetimeperiod.

Table 6: Drought Tolerant Species Planted in the

Catchment of Leaky Dam

Plant SpeciesHeight of

Plant (cm)Seedlings

(No.)

Atriplex lentiformis(Quailbrush)

79.57 250

Atriplex canescens(Fourwing saltbush)

78.74 300

Salsola vermiculta L. 29.61 50

The survival and growth of shrubs was foundsatisfactory after one year however, the impact onchecking of soil erosion, reducing runoff velocityand enhancing recharge was not noticeable atinitial stages of growth due to little bush volumewith less vegetative cover.


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Observation Well No.2

28

29

30

31

32

33

34

35

Oct-

02

0

Nov-

02

23.5

Dec-

02

32.2

Jan-

03

23.2

Mar-

03

11.1

May-

03

16

Jul-

03

23

Aug-

03

0

Sep-

03

0

Nov-

03

26

Jan-

04

64.4

Feb-

04

26.7

Mar-

04

0

Apr-

04

0

May-

04

0

RL=37.4

1m


32

33

34

35

36

37

38

39

40

Oct-

02

0

Nov-

02

23.5

Dec-

02

32.2

Jan-

03

23.2

Mar-

03

11.1

May-

03

16

Jul-

03

23

Aug-

03

0

Sep-

03

0

Nov-

03

26

Jan-

04

64.4

Feb-

04

26.7

Mar-

04

0

Apr-

04

0

May-

04

0

RL=42.8

0m

month

Year

rainfall (mm)

Observation Well No. 3

33

34

35

36

37

38

Oct-

02

0

Nov-

02

23.5

Dec-

02

32.2

Jan-

03

23.2

Mar-

03

11.1

May-

03

16

Jul-

03

23

Aug-

03

0

Sep-

03

0

Nov-

03

26

Jan-

04

64.4

Feb-

04

26.7

Mar-

04

0

Apr-

04

0

May-

04

0

RL=37.96m


26

27

28

29

30

Oct-

02

0

Nov-

02

23.5

Dec-

02

32.2

Jan-

03

23.2

Mar-

03

11.1

May-

03

16

Jul-

03

23

Aug-

03

0

Sep-

03

0

Nov-

03

26

Jan-

04

64.4

Feb-

04

26.7

Mar-

04

0

Apr-

04

0

May-

04

0

RL=33.54m


19.020.021.022.023.024.025.026.027.0

28.029.030.031.0

Oct-

02

0

Nov-

02

23.5

Dec-

02

32.2

Jan-

03

23.2

Mar-

03

11.1

May-

03

16

Jul-

03

23

Aug-

03

0

Sep-

03

0

Nov-

03

26

Jan-

04

64.4

Feb-

04

26.7

Mar-

04

0

Apr-

04

0

May-

04

0

RL=31.68m


23

24

25

26

27

28

29

30

31

Oct-

02

0

Nov-

02

23.5

Dec-

02

32.2

Jan-

03

23.2

Mar-

03

11.1

May-

03

16

Jul-

03

23

Aug-

03

0

Sep-

03

0

Nov-

03

26

Jan-

04

64.4

Feb-

04

26.7

Mar-

04

0

Apr-

04

0

May-

04

0

RL=34.4

8m


10.011.012.013.014.015.0

16.017.018.019.020.021.022.0

Oct-

02

0

Nov-

02

23.5

Dec-

02

32.2

Jan-

03

23.2

Mar-

03

11.1

May-

03

16

Jul-

03

23

Aug-

03

0

Sep-

03

0

Nov-

03

26

Jan-

04

64.4

Feb-

04

26.7

Mar-

04

0

Apr-

04

0

May-

04

0

RL=

24.83m

0

2

4

6

8

PZ-1 PZ-2 PZ-3 PZ-4 PZ-5 PZ-6 PZ-7

Observation Wells

RiseofWa

terTable(m)

Maximum Minimum

Figure 5: Groundwater Levels in 7 Observation Wells with Respect to Time


12/13



ECONOMIC ANALYSIS

The construction of Leaky Dam was started in

April 2002 and completed in October 2002. Afterselection of site, a proforma was prepared forsurvey of leaky dam downstream area. The totalnumbers of 16 families of local inhabitantscomprising farmers, tenants and livestock ownerswere interviewed before and after 1 year of thecompletion of Leaky Dam. The informationregarding cultivated area, crops and orchardsgrown, livestock and total estimated income werecollected and precise summary is given in Table7. After 6 years continuous drought, the first eventof rainfall was received in November 2002followed by December 2002, January, March,

May, July, November 2003 and subsequent morerainfall 64.4 mm during January 2004 followed by26.7 mm in February of the same year. But norainfall was recorded during the 8 months periodfrom March to October 2004 and again the signalsof drought in Balochistan have been reported inelectronic and print media by the MeteorologicalDepartment. The improvements in rangelands,orchards and crops have resulted in overallincrease in crop and orchard area as well asyields alongwith increase in livestock heads andtheir productivity. Consequently, 16 families livingdownstream area have been benefited

economically due to construction of leaky damand enhancement of groundwater recharge.Large scale adoption of such groundwaterrecharge techniques in all streams and tributariescan sustain and enhance the agriculture economyof the area and boost the living standards of thepeople.

Table 7: Economic Analysis of Leaky Dam atMargat, Quetta

ParametersBefore(2002)

After (2003)

Cultivated Area (ha) 22 35

Orchard area (ha) 12 17Crop Area (ha) 12 18

Livestock (heads) 159 183

Rise in Water Table (m) - 5

Net Income (Rs.) - 137,000

EXPERIENCE/LESSON LEARNT FOR FUTUREGUIDANCE

The experiences and lessons learnt for futureguidelines are discussed below:

The innovative leaky dams have potential toenhance groundwater recharge. The leakydam is acting as a barrier reducing thevelocity of water runoff and retaining water forsufficient time to allow its sediments to settleso they do not clog the macro pores in thedownstream bed.

The integrated approach to applygroundwater recharge technologies withminor and major changes and improvements

should be tested in one river basin fordemonstration.

The construction of low cost leaky dams andcheck dams with leaky embankments madewith boulders, cobbles, stones and large sizegravels available within and around thestreams and rivers for providing more area ofrecharge may be propagated in other riverbasins of Balochistan.

The newly established Balochistan WaterResources Management Authority should actas regulatory authority with strict control over

surface and groundwater resourcesmanagement and groundwater rechargemeasures in the Province.

The high tech recharge technologies likeinjection wells, vertical recharging wells andrecharging galleries may be tested andoperated during winter season near thepotential Delay Action Dams and karezes.

The stored water in the delay action damsshould be pumped out in the downstreamarea after settlement of sediments in thereservoir bed to recharge the depletedaquifers and to save it from evaporation

losses. The strict protection and complete control of

grazing along with extensive watershedmanagement in the catchments should belaunched for reducing the sedimentation loadin the reservoirs and enhancing the naturalrecharge of precipitation.


13/13



CONCLUSIONS

The innovative leaky dams have potential toenhance groundwater recharge. The leaky dam is

acting as a barrier reducing the velocity of runoffand retaining water for sufficient time to allow itssediments to settle so they do not clog the macropores in the downstream bed. This increasesrainwater movement into the aquifer. In this waymore rainwater may be conserved below theground surface for future use and saved from highevaporation losses which are high in uplandBalochistan.

However, the integration of leaky dam, checkdams, injection and gravity wells, groundwatermonitoring network, controlled grazing andxerophytic plants species propagation incatchments has been appreciated, acknowledgedand asked for adaptation by the policy anddecision makers. The end users and otherstakeholders are also convinced afterdemonstration to adopt these low costgroundwater recharge enhancement measures forrejuvenation of depleted aquifers in Balochistanand other similar areas.

REFERENCES

Asian Development Bank (ADB) (1995).Balochistan Groundwater Resources

Reassessment: Report, T.A No.2125-Pak,Halcrow Pakistan (Pvt.) Ltd.

Chaudhri, M.Y. and S.H. Hanjra (2002). Impact andneed assessment for areas affected by droughtand Afghan Refugees in Balochistan. FAO DraftReport.

Chaudhri, M.Y., S.H. Hanjra and F.R. Khan (2002).Crop and food assessment for drought affectedareas in Balochistan and Sindh. FAO/WFPReport.

Hussain, S.D., A.Majeed, M.I.Sajjad, M.Ahmad,M.A.Tasneem and W.Akram (1999). Study ofArtificial Recharge by Delay Action Dam at PechiUsing Isotopic and Chemical Techniques. In:Proceedings of the Regional Workshop on:Artificial Groundwater Recharge, held at WRRC,PCRWR, Quetta, Pakistan, 10-14 June, 1996.pp. 121-124.

Kahlown, M.A. and J.R. Hamilton (1994). Status andProspects of Karez irrigation. Water ResourcesBulletin of American Water ResourcesAssociation, 30(1): 125-134.

Khan, A.R. and M.A.H. Chaudhry (1967). Farmingerodable lands in West Pakistan, Bureau Agric.Inform., W. Pak. Lahore (Pub.). 1

sted. 180p.

Perkins, M. and D.R. Birch (1999). Groundwaterrecharge in the Quetta valley and surrounding

areas: Prospective techniques and their potentialfor mitigation of the decline in water table levels.In: Proceedings of the Regional Workshop onArtificial Groundwater Recharge, held at WRRC,PCRWR, Quetta, 10-14 June, 1996,. pp.14-20.

Todd, D.K. (1980). Groundwater storage andartificial recharge. UN Department of Economicsand Social Affairs. Natural Resources/WaterSeries. No.2.

WAPDA (1992). Uncontrolled Mining of Groundwaterin Balochistan and Possible Remedial Measures.Hydrogeology Project, Water and PowerDevelopment Authority (WAPDA), Quetta,Pakistan.

Williamson, R. (1987). Impact of watershed works onhydrology near Quetta. Final report for contract:Design of works and monitoring program forBalochistan Watershed Management Sub-Project. Sheddon Pacific TTY. Ltd.

WRECA (2000). Water Resources EngineeringConsultant Associates. Mission Report for FAO.

leaky recharge dam--kahlown & abdullah

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