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EFFECT OF HUMAN ACTIVITY ON RIVERS

S M. Govorushko Director of EIA Centre, Pacific Geographical Institute, 7 Radio St.,

Vladivostok, 690041, Russia; e-mail: [email protected]

Human impact on rivers is large-scale process that leads to diverse negative con-sequences. There are following ways of such impact: 1) river flow redistribution in time; 2) river flow redistribution in space; 3) river flow withdrawal; 4) physical dis-turbance of river-beds; 5) pollution; 6) water clogging; 7) thermal pollution. First way mainly occurs in case of reservoir creation, it is characteristic for the USA, Russia, Canada, Brazil, and China. Run-off redistribution in space used for water supply, navigation, hydropower generation, irrigation, etc. The most large-scale water trans-fers are typical for Canada, USA, Turkmenistan, and India. Irretrievable water con-sumption currently constitutes approx. 150 km3/year, which equals 1% of normal run-off of fresh water. Agriculture uses 70.1% of fresh water, industries take 20%, and municipal sector – 9.9%. Under physical disturbance of river-beds we mean any man-made changes of water level (cut-offs, changes in depth of the river by excava-tion or covering of ground, etc.). Open pits in river-beds for extraction of building materials and excavation works for navigation purposes are the most frequent ex-amples of such impact. Water contamination is tremendous and ever-increasing challenge. By its origin, three chief water pollutant groups may be distinguished: 1) municipal waste; 2) industrial waste; 3) agricultural waste. Under water clogging we mean accumulation of foreign substances, mainly insoluble. Thermal pollution con-nects mainly with cooling water released from electricity generating stations. Further research of human impact on rivers is necessary in order to minimize negative con-sequences of such impact in the future.

Key words: rivers, water transfers, pollution, water use, river flow

BASIN WATER MANAGEMENT 465

INTRODUCTION

Human impact on rivers is large-scale process that leads to diverse negative con-sequences. Human activity impacts on rivers in the following ways: 1) river flow redistribution in time; 2) spatial river flow redistribution; 3) river flow withdrawal; 4) physical disturbance of riverbeds; 5) pollution; 6) water clogging; 7) thermal pollu-tion.

RIVER FLOW REDISTRIBUTION IN TIME

River flow redistribution in time mainly occurs in case of reservoir creation (fig. 1). Later on those reservoirs are used for various purposes, specifically water-supply, flood protection, recreation, power generation, fish industry, water transportation, etc. The first reservoir was made 5 thousand years ago in Egypt [Goudie, 1997]. Pres-ently, there are approx. 37-38 thousand reservoirs increasing 1 million m3 in volume.

Fig. 1. Example of river flow redistribution in time.

The aerial view of Hoover Dam on The Colorado-River, Nevada, USA. This dam was constructed between 1930 and 1936. A height of its water level is 170 m. The reservoir is used for flood and silt control, power, irrigation, and industrial and do-mestic water supplies. Photographer Bruce Molnia

Today there are about 50,000 dams in the world whose height exceeds 15 meters. These dams can retain more than 6.5 trillion m3 of water that constitutes approx. 15 % of annual global river flow. The fact that the largest free-flowing river in the world (the Yukon in Alaska) is on the twenty-second position in terms of annual mean flow proves that impact made by dams on rivers is widespread world-wide [Dams …, 2006].

466 INTERNATIONAL CONGRESS ON RIVER BASIN MANAGEMENT

Reservoir creation modifies regime of river flow downstream of dam, including part of sea water near mouth. Water storages affects the following parameters: 1) natural hydrological regime; 2) volume of river flow; 3) alluvial river flow; 4) hydro-chemical regime; 5) thermal regime; 6) ice regime; 7) ichtiofauna.

Alteration of natural hydrological river regime leads to leveling river flow vol-umes within a year and modifies the character of riverbed processes. It is clearly seen in marks’ lowering of ridges’ rifts and bottom’s rising of reach’s sites, that is, to put it short, levels river flow profile. Another alteration caused by reservoir creation is decrease of flow quantity. This feature is induced by increase of evaporation. For instance, the river flow to the basin of the Caspian Sea has reduced by 10-12 km3 exceptionally due to creation of water reservoirs [Reservoirs …, 1986]. In most cases, the sediment runoff also sharply decreases.

Owing to alterations in hydrological regime all drawn and the overwhelming part of suspended alluvium stay within reservoir. The total mass of alluvium, accu-mulated in all reservoirs of the world, is estimated at 13.4 billion tons per year [Skur-latov et al., 1994; Yasamanov, 2003]. Absolute dimensions of alluvium, located in each reservoir, depend on the turbidity of the river and volume of streamflow. For instance, sediment river flow of Samur River (Dagestan, Russia) before hydrotechni-cal regulations amounted 7.6 million tons per year. Currently, it equals 0.5 million tons. Similarly, before construction of Chirkeiskaya hydroelectric power station in 1974 the delta of Sulak River annually received 13.2 million tons per year, while today it has only 1.64 million tons [Geoecological changes …, 1997]. In Spain, con-struction of hydroelectric power station’s dams on Ebro in 1940s led to reduction of Ebro’s sediment river flow from 20 million tons per year to less than 3 million tons per year [Dolotov, 1996].

Alteration of hydrochemical river regime causes leveling of seasonal chemical water mixture, as well as reduction of biogenic substances’ river flow. Water quality in reservoirs depends on specific conditions and therefore may be either better or worse than in rivers. Processes of natural purification, resulting from sedimentation, desiltition, dilution, destruction of organic substances, contribute to improving water quality. In turn, water quality worsens when influenced by deceleration of water exchange, development of organic life and processes of oxygen and thermal stratifi-cation.

Alteration of thermal river regime downstream is explained by the fact that in autumn reservoir water is warmer, and in spring is colder, than river water. More-over, those distinctions amount to 2-4°С, and the zone of influence of this effect sometimes equals hundreds kilometres [Avakyan et al., 1987].


Abrupt alteration of ice regime occurs due to unevenness of daily and weekly water flow. In areas with cold climate it frequently brings about jams which cause raising of water level. Reservoirs creation affects ihtiofauna, in particular modifies the rates of fish growing, amount and structure of populations, as well as life span, conditions of fish reproduction and growing. Dams’ construction on the majority of large rivers of the world created the barrier on the migration ways of valuable ana-drom and semi-anadrom fish (sturgeons, salmons, herrings). Their spawning sites became unapproachable for species. Fish perishes when passing through turbines and dams during migration. Fish dies when swims through high-pressure junctions. Those losses take place due to barotraumas of swimming-bladders when fish leaves the reservoir for lower pool of the dam. However, one should also mention positive impact of dams’ creation on ichtiofauna, since the area of biotopes favorable for fish fattening and spawning considerable increases. Commonly, fish hauls in reservoirs increase those made before reservoir creation. To the utmost river flow redistribution in time is typical for the USA, Russia, Canada, Brazil, and China.

RIVER FLOW REDISTRIBUTION IN SPACE

Spatial river flow redistribution is usual as well (fig. 2). Under the notion ‘spatial river flow redistribution’ we imply the process of water withdrawal from one source (rivers, reservoirs, lakes, etc.) and its further transportation by riverbed, channel, tunnel or pipeline to consumers. One can subdivide such water transportations into transfers for water-supply, providing navigation, hydro-power engineering, irrigated farming, drainage of over-humid lands. The channel which connected the Tiger River and the Euphratus River was dug approx. 2400 B.C. and became one of the earliest examples of channel-building. It was dug with a view to ameliorate irrigation sys-tem, since water rise in the Tiger River did not coincide with that one in the Euphra-tus River [Anderson, Trigg, 1981]. The volume of transported water and the distance it is transported to are the crucial parameters of river flow transportation system. The most widespread index to estimate the scale of river flow modification is calculated as multiplication of annual river flow transported (km3 per year) by the distance of transportation way (km). Presently, majority of river flow transfers are carried out for irrigation needs and classified as small or average (up to 1000 km3 per year). So far Karakum Channel in Turkmenistan remains the largest channel, judging by this index. It transports 1100 km3 per year over a distance of 1100 km. Still, creation of a new channel in China has already started. This channel will transfer 44.8 km3 per year over a distance of 1300 km from the Yandzy River to Northern-Chinese plain [Govorushko, 2005].


Fig. 2. Example of spatial river flow

redistribution.

Photo of Tennessee – Tombigbee Waterway in eastern Mississippi, USA. This 376-kilometres-long

inland water route provides a link between two existing navigational

systems.

Photographer Lynn Betts, 15 of September 1992.

Describing spatial river flow redistribution, it is necessary to distinguish three

zones which differ from each other in the impact made upon natural habitat: 1) zone of water withdrawal; 2) zone of water transportation; 3) zone of water usage. This impact is following [Shiklomanov, Markova, 1987]. Zone of withdrawal is character-ized by decrease of river flow, lowering of water level, intensification of riverbed processes, diminution of waterlogged sites, expansion of salty sea waters’ penetra-tion, etc. Zone of transportation is characterized by increase of river flow, rise of water-level, underflooding and waterlogging of nearby lands, intensification of ero-sion and evaporation, etc. Zone of water usage is characterized by intensification of erosion and evaporation, worsening of surface water’s quality, etc.

There were cases when river flow was almost completely taken away in the zone of withdrawal. One may cite as an example the Colorado River which stopped flow-ing into Calilfornian gulf, since water was used to irrigate fields of the USA and Mexico [Rosenberg et al., 2000]. The Syrdarya River and the Amudarya River did not reach Aral Sea in low-water years (for instance, 1980 and 1985) [Sempere-Antuan,


2000]. Decrease of the Jordan River flow caused lowering of the Dead Sea [Goudie, 1997].

The measures, aimed at water losses’ decreasing in the zone of transportation, are very important. Quite often sizeable volumes of transported water are lost be-cause of ground leakage. Thus, in the first years after Karakum Channel creation 3 km3 per year (out of 11) were lost in that manner; nowadays, those losses reduced to 1 km3 per year due to silting of the leakage [Gorshkov, 1992]. Altogether, more than 2200 channels with total length of 170 thousand km have been built in the basin of the Aral Sea; but for all that no measures to mitigate filtration were taken in most cases [Stadnitskiy, Rodionov, 1996]. Water losses in irrigation system of Pakistan amount to 55-65 % [Shiklomanov, Markova, 1987]. In the zone of water usage, river flow considerably increases. Thus, the annual river flow of the Berntvood River, inflow of the Nelson River, which transports water to the Nelson River increased from 3.3 to 27.3 km3 per year, or by 800% [Shiklomanov, Markova, 1987]. The most large-scale river inflow transfers are typical for Canada, the USA, India, and Turk-menistan.

RIVER FLOW WITHDRAWAL

Irrevocable water consumption presently totals approx. 150 km3 per year, or 1% of sustainable river flow [Stadnitskiy, Rodionov, 1996]. Most water is taken for needs of agriculture (70.1%), industries (20%) and residential areas (9.9%) [Comprehensive Assessment …, 1997]. It takes 1500 m3 of water to produce a ton of wheat; 7000 m3 and 10000 m3 to produce a ton of rice and cotton respectively [Rudskiy, Sturman, 2005]. Production of a ton of meat requires averagely 20000 m3 of water [Stadnitskiy, Rodionov, 1996].

In industry, intensive water consumption is typical for heat-and-power engi-neering, petrochemistry, pulp and paper industry. Altogether they account for 80-90% of total industrial water usage [Merkulov et al., 1994]. Production of synthetic caoutchouc (2000-3000 m3 per ton) and capacitor paper (1300-6000 m3 per ton) are the most water-consumptive manufactures [Stadnitskiy, Rodionov, 1996]. Production of chemical fiber (2000-3000 m3 per ton) and cellulose (400-500 m3 per ton) also require much water [Milanova, Ryabchikov, 1986]. Considerable water consumption also distinguishes a number of light industries, namely spinning, weaving and trimming manufactures which averagely require 300-330 m3 per ton of output [Marinich et al, 2000]. In housing and communal services water is mainly used for hygiene and sani-tary purposes (baths, laundries, etc.), food cooking, sewerage system, etc.


PHYSICAL DISTURBANCE OF RIVERBEDS

As for physical disturbance of riverbeds, here we put any anthropogenic altera-tions of planned or high marks. The most intensive impact on riverbeds is made during extraction of building materials or other fossils in riverbed carriers (fig. 3), dredging works with a view to facilitate navigation, and construction of pipelines’ underwater sections. Such activities change the evolution of riverbed processes that affects hydrobionts’ natural habitat. In the course of extraction of ground from river-beds and its transportation to dumps water becomes muddier for some time. Extrac-tion of large massifs of riverbeds’ ground causes deepening and straightening of riverbeds, as well as decreasing of its branching and lowering water level during low-water seasons. Dredging works for navigation facilitation are considered to be less harmful for hydrological regime than extraction of non-metallic building materi-als, since in the first case ground taken from riverbeds is not withdrawn irrevocably but is only removed from the navigation route to outside [Botvinkov et al., 2002]. Physical disturbances of riverbeds are rather large-scale in some areas, but on the whole their importance is not very high.

Fig. 3. Example of physical disturbance of riverbeds.

Photo shows drag gold ex-ploitation in the upper of the

Yahsu River (basin of the Amudarya River, Tajikistan).

Photographer Lev Desinov, July of 1988.

WATER POLLUTION

Water pollution constitutes ever-increasing problem. By its origin, it is advisable to subdivide water pollutants into three groups [Goudie, Viles, 1997]: 1) municipal wastes; 2) industrial wastes; 3) agricultural wastes.

Municipal wastes mainly consist of human faeces and contain relatively few chemical pollutants; yet, they are notable for high concentration of pathogenic organ-isms. Communal wastes, or sewage, make approx. 20% of all effluents’ volume, and their share constantly increases as the amount of industrial effluents decreases. They have more or less permanent structure. A person daily produces 65 gram of sus-pended matter, 8 gram of ammonia nitrogen, 3.3 gram of phosphates, 9 gram of chlo-rides, 60-75 gram of organic matter [Rudskiy, Sturman, 2005].


The impact of communal wastes upon rivers varies from country to country. Out of 3119 cities and towns of India only 209 possess structures for partial purification of sewage, and only 8 of them have total cycle purification systems at their disposal. Commonly, sewage comes directly to rivers. For instance, the Gang River is being daily polluted by unpurified sewage waters and cremation remains from 114 cities and towns [Pimentel et al., 1999]. Naturally, this situation is not so grave in devel-oped countries, though river pollution is a sensitive issue there as well. For instance, the New York Metropolitan area alone produces 6.8 billion littres of sewage per day of which about 16% is raw. Much of this enters the Hudson and East Rivers around New York [Goudie, 1997].

Industrial wastes (fig. 4) are subdivided into [Stadnitsky, Rodionov, 1996]: 1) waters of reaction, polluted both by parent substances and reaction products; 2) waters coming from raw materials and raw products; 3) scourage which appears after ablutions of raw materials, packages, equipment, etc.; 4) water extractants and absorbents; 5) sewage waters; 6) atmospheric precipitation, flowing down on indus-trial enterprises’ territories.

Fig. 4. Rivers can be polluted by many different manners.

Sewage is one of the most typical ways of river pollution. On this

photo you can see unpurified sewage produced by industrial enterprise of

Volgograd, Russia. On the back-ground – the Volga River.

Photo of GREENPEACE – Russia


Industrial calamities greatly contribute to river pollution. Accidents on tailing dumps of ore mining and processing enterprises are the most detrimental ones. Two disasters on tailing dumps of gold-mining enterprises in Guyana and Romania should be noted especially. The enormous negative impact of these two accidents was caused by peculiarities of gold-enrichment technology. Specifically, in order to separate thin plates of gold from other materials, high-toxic solid salt of hydrocyanic acid was applied. It is necessary to mention that 2 parts of this acid to 1000000 parts of water are capable of killing many water organisms.

Guyana accident broke out on the 19th of August, 1995. The dam burst, and approx. 3.3 billion litre of slime-like liquid mixture started moving from tailing dump to the Essekibo River and had been moving for 5 days. That annihilated river ichtiofauna on the distance of 80 km down the river (Carson, 1995). The accident in Romania occurred on the 30th of January, 2000. The dam breach led to penetration of 100 thousand m3 of liquid and suspended wastes, containing from 50 to 100 tons of cyanides, as well as copper and other heavy metals, into nearby river (fig. 5). In this event, seriously suffered fish resources, mostly not Romanian but Hungarian (the Tisza River and its inflows). In addition to it, water supply was interrupted in 24 municipalities [Water …, 2006]. Similar accidents happened also at Californian gold-mines, USA, in 1991, copper and zinc mines in Philippines in 1996, zinc mines in Spain in 1998 [Accidental …, 2001]. Oil pipelines’ accidents are dangerous, too. In Russia, 15 million tons of crude oil leak out annually, with most of leakages taking place in underwater sites into rivers and shelf sea area.

Fig. 5. River pollution as a result of accidents occurs not so

frequently, yet brings about more severe consequences.

On this photo you can see the breach in a tailings dam near Baia Mare (Romania), through which on the 30

January, 2000, 100,000 m3 of cyanide-rich tailings waste

fell into the Somes, the Tisza and finally reached the

Danube Rivers.

Photo of UNEP

Agricultural wastes are characterized by excessive amount of phosphorus and nitrogen, being part of fertilizers and cattle breeding wastes, as well as by high con-centration of pesticides and herbicides. Agricultural wastes also pose a serious threat


for river habitats. For example, a 378,000 liters spill of wet manure in Minnesota killed almost 700,000 fish along 30 kilometres of a major stream. American agricul-ture now discharges 1.16 million tons of phosphorous and 4.65 million tons of nitro-gen into waterways annually. Agriculture also exerts indirect influence on rivers. Ploughing intensifies soil erosion that increases amount of different substances enter-ing rivers. Early soil discharge from agricultural land to waterways in the United States is estimated at over 1 billion tons of sediments and 447 million tons of total dissolved solids. The Mississippi River alone carries 331 million tons of topsoil to the Gulf of Mexico annually [Ruhl, 2000].

WATER CLOGGING

Under water clogging we imply processes of insoluble materials’ amassment in river waters, namely amassment of solid industrial and communal wastes, construc-tion wastes, etc. Litter is logically subdivided into floating litter which pollutes sur-face water, and sinking litter which pollutes bottom of the river. Quite often, floating litter adsorbs oil which adheres to it. Accumulation of sinking litter sometimes modi-fies natural habitat of fish and water plants [Botvinkov et al., 2002]. River transport greatly contributes to water littering. Vessels amass remains of bulk (grain, coal, timber, ores, scrap, etc.). When ships change their bulk, those remains are frequently thrown overboard. Timber rafting also affects rivers producing various kinds of litter, mainly bark, branches and logs (fig. 6). Hence, 0.5% of lumber remains within riverbed after each timber rafting [Manukovsky, Patyakin, 2004]. On the whole, the importance of littering for river habitats is inessential in comparison with other kinds of impact.

Fig. 6. The importance of

littering in comparison with other kinds of impact on

rivers is insignificant.

The typical example of such impact is timber rafting which

causes river littering with wastes, bark, branches, and

logs. Up to 0.5% of all lumber remains within riverbed after transportation. Timber rafting

on Ma River (Vietnam) is demonstrated on this photo. Photographer Peyton John-

son, 1995 (credit FAO, picture 19203)


THERMAL POLLUTION

Thermal pollution emerges as a result of functioning of heat-and-power engi-neering aggregates and heat exchanging plants. Heat-and-power engineering aggre-gates (thermoelectric power stations, nuclear power plants, heat-engines) convert heat into electric or mechanical power. Heat exchanging plants apply heat to modify physicochemical properties of materials and convert substances from one aggrega-tive state into another. By such plants we imply heaters, plants for drying, melting, evaporation, and agglomeration of multifarious materials [Problems…, 1995].

Heat ejected into the atmosphere disperses relatively quickly and therefore does not have substantial impact on the environmental situation in general. Still, its par-ticular impact on reservoirs is much more considerable. High water temperature leads to diminution of species variety of algae and phytoplankton, decrease of aver-age life-span of animal plankton, increase in amount of blue-green algae which con-tains different toxins and affects herbivorous organisms.

Since dissolubility of gases in liquid is inversely proportional to its temperature, water heating decreases amount of oxygen, nitrogen and carbonic gas in water. Be-sides, rise of water temperature increases the need of organisms in dissolved oxygen. So concentration of oxygen decreases even more.

Importance of thermal pollution mostly depends on the state of a waterway which receives thermally polluted water. For instance, ejection of warm water from one of thermoelectric power stations into the Severn River, Great Britain, rises water temperature in the river on 0.5 degrees during freshets and 8 degrees during low-water season [Goudie, 1997]. In the USA, 200 km3 of water are annually withdrawn for cooling needs, and approx. 80% of this amount is used in power industry [Gorshkov, 1992].

Though in comparison with a number of above-mentioned kinds of human im-pact on rivers the importance of thermal pollution is not very high, in some areas of the world it is predominantly substantial. Thermal impact causes slowing of photo-synthetic plankton activity, perish of fish and other hydrobionts, deficit of oxygen, deterioration of sanitary-microbiological state of water.

Further research on anthropogenic impact on rivers is necessary in order to mitigate negative consequences of it.

Research funded by Russian Foundation of Basic Research, project 06-05-96127.


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