An assessment of the ecological impacts of inter ...

AQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, VOL. 2, 325-349 (1992)

VIEWPOINT

An assessment of the ecological impacts of inter-basin water transfers, and their threats to river basin integrity and conservation BRYAN R. DAVIES Freshwater Research Unit, Zoology Department, University of Cape Town, Rondebosch, 7700, South Africa

MARTIN THOMS Department of Geography, University of Sydney, Australia

and MICHAEL MEADOR United States Geological Survey, Raleigh, North Carolina, USA ABSTRACT 1. Detailed research into the ecological impacts of inter-basin water transfers (IBTs) is virtually nonexistent on a global scale. However, a growing awareness of the serious nature of such impacts- for example, the loss of biogeographical integrity, the loss of endemic biotas, the frequent introduction of alien and often invasive aquatic and terrestrial plants and animals, the genetic intermixing of once separated populations, the implications for water quality, the frequently drastic alteration of hydrological regimes, the implications for marine and estuarine processes, climatic effects, and the spread of disease vectors, amongst many others-demands a most urgent and world-wide appraisal of all current planning and research strategies. 2. This paper first defines the types of extant IBTs, and details some case studies for three widely separated regions of the world, namely: south-eastern Australia, southern Africa, and the central and south-western parts of the United States of America. In doing so, it highlights the chronic paucity of ecological data on their impacts, while simultaneously emphasising their extreme complexities. 3. Finally, we call for an international meeting on such schemes, as a matter of priority and extreme urgency, in order to assess the extent of IBTs, their geographical distribution, and their ecological and sociological impacts and implications.

INTRODUCTION The transfer of water from areas of surplus supply to those in deficit has become an increasingly frequent ‘solution’ to the redistribution of much needed water supplies. This is particularly so in arid and semi-arid areas, and many human populations now rely solely on such imported water. In international terms, water transfers have begun to assume increasing significance (e.g. Golubev and Biswas, 1985; Petitjean and Davies, 1988a, b). For example, the total transfer of water in Canada amounts to almost 14 x lo9 m3yr- (Golubev and Biswas, 1985), while in the former Soviet Union a recent project planned to divert Northern Siberian 1052-7613/92/040325-25$17.50 01992 by John Wiley & Sons, Ltd

Received 13 February 1992 Accepted 7 September 1992

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Rivers south amounted to between 50-60 x lo9 m3 yr- (Voropaev and Velikanov, 1985). In the People’s Republic of China, a proposed south-north water transfer would involve a ‘Middle Route’ transferring some 23.7 x lo9 m3 yr- l , and an ‘East Route’, with a maximum of 30 x lo9 m3 yr- * (Chang Ming et al., 1985). Such massive projects are frequently well assessed technically at the planning stage, but are usually very poorly assessed in terms of their potential ecological impacts. Environmental concerns have been limited to some Soviet, Canadian and American projects, though even here we submit that ecological consequences have been underplayed. To date, very little global concern has been paid both to the direct and the indirect ecological impacts of such schemes; Australia, Southern Africa and the USA are no exceptions. DEFINITIONS

Long-distance water transfer, inter-regional water transfer, inter-river transfer, large-scale water transfer, inter-catchment water transfer, inter-basin water transfer and intra-basin water transfer are all terms which have been used to describe the conveyance of water from an area of present surplus to one where the water demand has exceeded, or soon will exceed, supply (e.g. Cummings, 1974; Golubev and Biswas, 1979, 1985; Biswas et al., 1983; El-Ashry and Gibbons, 1988). In attempting to establish guidelines for identifying water transfers in Canada, Quinn (1981) used two major criteria: 1. the diverted flow does not return to the stream of origin, or to the parent stream within 20 km of the point of withdrawal, and 2. the mean annual flow transferred should not be less than 0.5 m3 s - l .

In practice, however, all water development projects involve the transfer of some water over a wide variety of distances. Figure 1 illustrates the types and complexities of IBTs that we should like to consider in this paper. Contrary to Quinn (1981), we argue against a distance and volume component for any definition, first, because 0.5 m3 s - amounts to a considerable volume annually, second, because this volume takes no account of the relative natural flow of the receiving reach (a small headwater reach would be severely impacted by such a delivery), and third, because the flow volumes of many transfers vary enormously, both temporally and spatially, particularly in arid and semi-arid regions. In addition, transfers may be

IBT‘s - Spatial Types Reci ient SysFem

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. headwaters Pulsed vs

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Figure 1. A diagrammatic representation of the major types of inter-basin water transfers that are possible; some 60 or more permutations can be developed from this scheme.

ECOLOGICAL IMPACTS OF INTER-BASIN WATER TRANSFERS

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intermittent orpulsed, or may be seasonal or aseasonal (Figure 1). Further, intra-basintransfers are common and, as such, should not fall outside the net of our definition of IBTs. Figure 1 illustrates the fact that there are 15 possible forms of IBT, but if we add constant versus pulsed flows, and seasonal versus aseasonal deliveries, or abstractions, then the sum reaches some 60 different permutations! For our purposes, the definition that best describes those water transfers most likely to cause deleterious ecological impacts is: the transfer of water from one geographically distinct river catchment or basin to another, or from one river reach to another. In real terms, this definition includes such schemes as the Jonglei Canal on the River Nile (e.g. Critchfield, 1978; Charnock, 1983; Bailey and Cobb, 1984) which constitutes a major human manipulation of water within a distinct basin, but a manipulation which could have major ecological repercussions. Any transfer of water within o r between basins will have physical, chemical, hydrological and biological implications for both donor and recipient systems, as well as for their estuaries and local marine environments. The underlying tenet of river ecosystem functioning, the River Continuum Concept (RCC) of Vannote et al. (1980), states that all rivers exhibit a gradation of biotic responses to a continuum of physical and chemical gradients, such that stream communities are variously structured and controlled down the system by the events that take place in upstream reaches. Based on this concept, the removal or addition of water at any point along a river is likely to perturb the continuum, and hence, the functioning of the systems involved. Related t o (and based upon) the RCC is the Serial Discontinuity Concept (SDC) of Ward and Stanford (1983). This states that impoundments cause discontinuities in the river continuum, and that any measurable characteristic of streams will require a ‘reset’ or ‘recovery distance’ (sensu O’Keeffe et al., 1990). For example, temperature will be profoundly influenced by prevailing reservoir water released either by natural spillage, or from sluice gates. This temperature change will eventually equilibrate to ‘pre-impoundment’ values after a given distance downstream. We argue that similar disruptions to the continuum must also occur in the case of IBTs. For example, a ‘cool’ headwater transfer t o a ‘warmer’ mid-reach (Figure 1) will also have a temperature recovery component to it, or may even have a multiplying effect. The same may be true for many other stream characteristics, such as water quality, nutrients, suspended particulates, and so on. The impacts of IBTs, where water has not been removed from the basin but is simply relocated within it, can be just as ecologically deleterious as any major transfer or impoundment (e.g. Ward and Stanford, 1979; Lillehammer and Saltveit, 1984; Petts, 1984; Davies and Walker, 1986; Craig and Kemper, 1987; Gore and Petts, 1989). WATER TRANSFERS IN SOUTHERN AFRICA

Background Southern Africa lies between 20” and 36” S and has a very low conversion of mean annual precipitation (MAP) to mean annual runoff (MAR). MAP for the sub-continent is 497mm, of which only 8.6% is converted to runoff (i.e. 44mm; Alexander, 1985-see Figure 2). The remainder is ‘lost’ through evaporation and to groundwater. The percentage of MAP converted to runoff varies widely; in none of the primary drainage regions of South Africa does it exceed 25010, and for the majority it falls below the mean for the country (Figure 2). Indeed, South Africa has one of the lowest conversions of rainfall t o runoff for any area of the world (Figure 2), Petitjean and Davies (1988b) quoting the conversion for Canada as 65.7%, and that for Australia as 9.8% (see below). Further, the distribution of water across the sub-continent is spatially skewed (e.g. Allanson et al., 1990; Davies et al., in press). Rivers of the eastern escarpment (Figure 3) yield 66% of the total runoff, while 33% of the land mass yields a mere 1%. In addition, the bulk of the population is located in the Pretoria-Witwatersrand-Vereeniging(PWV) area, a region where evaporation greatly exceeds precipitation and river flow can be extremely erratic (Davies el al., in press).

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Figure 2 . Relationship between mean and annual runoff (MAR) and mean annual precipitation (MAP) for selected representative regions of the world (named), as well as for major river basins in South Africa (filled triangles). (Modified after Alexander, 1985).

Existing IBTs in southern Africa (Figure 3), presently divert 1.63 x lo9 m3 yr- (Petitjean and Davies, 1988a, b; Davies et al., in press). This total is projected to grow to some 4.82 x lo9 m3 yr-' by the year 2017, involving 8.9% of the total MAR (54x 109m3yr-': Department of Water Affairs, 1986). This is slightly more than the cumulative annual runoff from the Tugela River, one of South Africa's largest rivers (Department of Water Affairs, 1986). The total rises to a theoretical maximum of 8.77 x lo9 m3yr-' should the Zambezi Aqueduct be constructed (Figure 3, scheme 13). All extant schemes, and those that are planned or are under construction, are illustrated in Figure 3, while data on the drainage regions and volumes involved are published in Petitjean and Davies, 1988a, b; Davies et al., in press). Case histories

We have chosen two case histories from southern Africa that illustrate some of the major problems of IBTs, not only for the sub-continent, but also globally; they are the Eastern National Water Carrier (ENWC) of Namibia (Figure 3, scheme 7) and the Lesotho Highlands Water Project (LHWP) in Lesotho and South Africa (Figure 3, scheme 11).

The Eastern National Water Carrier (EN WC), Namibia Early forecasts of water shortages in the Okahanja/Windhoek area for the beginning of the 1980s triggered the planning of the Eastern National Water Carrier (ENWC) at an estimated cost of R368miHion


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Figure 3. Major population centres, rivers, and extant and proposed IBTs (arrows) in southern Africa. 1, Tugela-Vaal; 2, Orange River Project; 3, Usutu; 4, Komati; 5 , Usutu-Vaal; 6 , Riviersonderend-Berg River Project; 7, Eastern National Water Carrier; 8, Palmiet. 9, Amatole; 10, Mzimkulu-Mkomaas-Illovo; 11, Lesotho Highlands Water Project; 12, Mooi-Mgeni; 13, Zambezi Aqueduct. (After Petitjean and Davies, 1988b).

(approximately US$l50 million at 1985 prices). The first two phases are complete, while phase 111 is under construction, with a completion date scheduled for the end of the century, depending upon revised estimates of the increase in water demand. Phase I, completed in 1978, involved the Von Bach Dam on the Swakop River (Figure 4;gross storage capacity, 54 x lo6 m3), the Swakoppoort Dam (capacity, 70 x lo6m3), 55 km below Von Bach, and a pump system to Windhoek, 53 km away. Phase 11, comprising the earthfill Omatako Dam (capacity, 40 x lo6m3; Figure 4), on the Omatako River, and a pump scheme (capacity, 2 m3 s - l ) , which transfers water from the Omatako River to the Von Bach Dam, was completed in 1983. Construction of Phase 111, comprising the controversial 263 km Grootfontein-Omatako Canal and the Karstland Borehole system (Figure 4), began in 1981 with a scheduled completion date of 1987, but construction was slowed because water demand failed to rise according to initial predictions. For some 203 km, the canal is an open concrete-lined structure designed to discharge between 2-3 m3 s- l . The Karstland Borehole scheme will yield between 15-20 x lo6 m3yr- (Ravenscroft et al., 1985) from the Dolomitic Aquifers near Grootfontein, and will provide water from 70 boreholes at the head of the canal. Abstraction from the scheme may reach 35 x lo6 m3 yr- although this is planned not to exceed groundwater

',

3 30


L

Omatako River

Omatako

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\

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indhoek

Figure 4. Schematic outline of the Eastern National Water Carrier, Namibia, showing main population centres (circles), major dams, and canals and pipelines (broken lines). Arrows indicate direction of water flow. (After Petitjean and Davies, 1988b).

recharge rates. Phase IV, the Kavango River abstraction near Rundu (Figure 4), has a design delivery capacity of 2-3 m3 s- I and is due for completion in 1999. The construction of the ENWC initiated the implementation of several programmes to ascertain the impact of different components of the scheme, but only after construction had already begun. An assessment of the potential impacts was conducted by Bethune and Chive11 (1985), together with a literature review of similar schemes elsewhere (Bethune et al., 1984). As a result, a monitoring programme was set up to establish the prevailing conditions before completion of the transfer from the Kavango River to the Von Bach and Swakoppoort dams, and this identified a number of ecological concerns requiring further investigation (Department of Water Affairs, South Africa and Department of Agriculture and Nature Conservation, S.W.A./Namibia, 1987). These concerns are listed below, together with our comments. 1. The transfer of alien fish species from the Kavango River to the central drainage systems. The probable transfer of fish from the Omatako to the Swakop River was never originally considered, probably because of the ephemeral nature of these rivers. Although it is unlikely that any of the Kavango River species could become established within the dams and pipelines/canals, it is possible that other species with broader tolerances could be transferred. Fortunately, (although perhaps a little late), methods aimed at reducing the possible transfer of fish are now being assessed after the publication of concerns expressed by


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Skelton and Merron (1 985) that the three spot bream, Oreochromis andersonii, the barbel, Clarias gariepinus, and the banded bream, Tilapia sparmanii, and others ‘. . . will provide direct intraspecific competition with existing populations . . .’ in the Omatako Dam and in the Swakop River. 2. The possible transmission of schistosomiasis. On paper, the canal is unlikely to act as a transmission route; end-point chlorination and the likely high flow rates should prevent the establishment of suitable conditions for host snail populations. However, the establishment of snail vectors in the reservoirs of the scheme seems to be inevitable, with obvious consequences for the propagation and spread of schistosomiasis. 3. Growth of algae within the open sections of the canal, and deterioration in water quality. The nutrient levels of the transferred water are relatively low (Bethune, 1991), but the open nature of the canal will act as an animal trap (see point 4 below). The decomposition of trapped animals, together with that of wind-blown material, may have serious implications for water quality and for algal growth. 4. The effects of the open canal on migration routes and animal mortality. This is one of the most contentious, emotive and serious impacts of the scheme. Several articles have been published on the postoperational impact of the open canal on the large animals of the surrounds (e.g. Comrie-Greig, 1986; Jones, 1987); impacts which many environmentalists felt should have been obvious from the first planning stages. An early estimate of the annual death toll for the entire canal gave a figure of more than 17500 animals! This figure, which concentrated mainly on large mammals and reptiles, but which took no account of the myriad insects and other invertebrates that would die and decompose in the canal, led to the nickname ‘Killer Canal’ for the open conduit (Comrie-Greig, 1986). More recently, an important report has described detailed studies of the effects of the canal (Department of Water Affairs, Republic of Namibia, 1992). Examination of 65 km of the canal between June 1985-August 1986 revealed a total of 7234 vertebrates (excluding decomposed animals, and those consumed by carrion feeders). Some 28 mammal species were recorded, including rare pangolin, aardwolf, bat-eared fox and antbears. Of the total, 57% were reptiles, 22% amphibia, 19% mammals, and 2% were birds (Department of Water Affairs, Republic of Namibia, 1992). Certain endangered species, such as the Cape Vulture, Gyps coprotheres, a carrion feeder, may also fall prey to the canal when feeding on large game which has drowned (after feeding, the birds require a ‘runway’ to take off). Although the ideal solution would have been to cover the system, the original R30 million required was considered ‘. . . too high at this stage to make such action a practicable solution . . .’ (Department of Water Affairs, South Africa and Department of Agriculture and Conservation S.W.A./Namibia, 1987). In 1987, a number of experimental ‘escape’ structures were incorporated, but were frequently not used by panicked animals and, ironically, the cover-option was started on an experimental basis in 1990, over a 1.5 km stretch, with great success. Experimental reptile barriers also had early successes (Department of Water Affairs, Republic of Namibia, 1992), and now there is a strong recommendation that the entire canal be covered, despite the increase in cost to R50 million! Various other solutions, such as small electrified fences, grids and sloping ramps were originally discussed, and some are in place, but have had far less success than the cover (Department of Water Affairs, Republic of Namibia, 1992). One cannot help a feeling of frustration that not only was the original planning so ecologically poor, and that warnings went unheeded, but that the general public has now to pay heavily to modify an already extremely costly system-at an expense very much greater than that which was originally rejected by the decision makers! 5. Effects of groundwater withdrawalfrom the Karstveld Borehold Scheme on theflora and fauna. Research

is in progress on this issue, following early reports from local farmers of severe water-table depression and drying springs. Monitoring of local vegetation will continue after major abstractions have begun. However, both seasonal and annual depression of the water table in this water-stressed region is inevitable with a scheme

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of this magnitude. Current research has shown that the water table in some areas has already dropped from between 0-5 m to between 10-1 1 m below river-bed level (E. Chivell, Department of Water Affairs, S.W.A./Namibia, personal communication, 1988). 6. Evaporative water losses from the Omatako Canal and from reservoirs. Open-pan evaporative losses for the region amount to between 2250-3000 mm yr- I , while precipitation rarely excedes 200 mm yr- (e.g. Davies and Day, 1986; Davies et al., in press), yet although objections were raised concerning evaporative losses from the open Omatako Canal (not to mention the storage reservoirs), original estimates revealed ‘. . . that such losses will be relatively insignificant . . .’ (see Ravenscroft et al., 1985). Subsequent investigations have, however, shown that evaporative losses from the canal alone will be close to 70%-a very long way from ‘insignificant’ (E. Chivell, personal communication). Further, problems of hydrostatic pressure on the concrete-lined canal, while it was still not in use, caused ‘floating of its bed, during periods of rainfall, and resulted in cracking of the base. The effects of the ENWC are still becoming apparent, and the lack of a full inter-disciplinary ecological impact assessment at the planning stage has led to public outcry. Furthermore, the scheme is not yet complete, and proposed abstraction of some 3 m3 s - from the Kavango River has still to occur, while borehole withdrawals are not fully operational. According to Bethune (1991), the proposed withdrawals from the Kavango River will have minimal impact during flood periods, amounting to < l o % of the mean annual flow. However, during dry years and droughts, the situation will be very different, respectively amounting to 20% and 47% of the mean annual flow (Cashman et al., 1986; Bethune, 1991). In addition, as the drawoff at Rundu is upstream of the confluence of the Kavango with the Cuito River, the transfer is likely to have a serious impact on the artisanal fisheries of the Shambuyu and Gciriku people in the intervening reaches. It has been recommended that any transfer should take place below the confluence of the two rivers, so that the Cuito flow can augment the flow of the mainstem (Bethune, 1991).

The Lesotho Highlands Water Project (LH WP) The treaty for the Lesotho Highlands Water Project (LHWP) was signed on 24 October 1987, and was the subject of many years of international negotiations and technical investigations. The project, with an estimated cost of R5.5 billion at 1987 prices (which could rise to R15 billion), will transfer 2200x lohm3 yr- I from the headwaters of the Orange River in Lesotho to the Ash River (Figure 5) (Department of Water Affairs, 1985), a tributary of the Vaal River, the major confluent of the Orange River. The water will primarily be for industrial and domestic consumption in the Pretoria-Witwatersrand-Vereeniging triangle (the high price of the water-R0.7 m-3-preclude~ agricultural use). Phase I is divided into two. Phase IA comprises the Katse Dam on the Malibamatso River, the Sentelina Dam (with a hydropower unit) on the Noqoe River, and the Tlhaka Dam on the Hololo River (all impounding tributaries of the Orange River). Tunnels will connect Katse and Sentelina (48 km), and a tunnel (34 km) will also run beneath the Caledon and Little Caledon rivers, from Tlhaka Dam to the Ash River. Phase IB entails the Mohale Dam on the Senqunyane River, and a 32 km tunnel connecting it to Katse (Figure 5). Approach roads are complete, and construction of the Katse Dam commenced in 1992 (Lesotho Highlands Water Project, 1992). Phase I1 includes the Mashai Dam on the Lower Malibamatso River and a tunnel connecting this to the Tlhaka Dam or, via a pump station, to Katse (Figure 5 ) , and then on to Sentelina via the existing tunnel (for which purpose, the capacity of the latter tunnel would double). The final phase comprises the Tsoelike Dam and a tunnel and pump station to transfer water up to the Mashai Dam (Figure 5). Downstream, further harnessing of the Orange River is possible allowing water to be pumped back upstream into the scheme (Department of Water Affairs, 1985).


To Vasl

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Figure 5. Schematic outline of the proposed Lesotho Highlands Water Project, showing main dams, and tunnels and pipelines (broken lines). Arrows denote direction of water flow. Construction of the first phase is already underway. (After Petitjean and Davies, 1988b).

Exploitation of the Upper Orange River in Lesotho will reduce the yield of the Orange River Project (see Figure 3, scheme 2), an IBT which takes water from the middle Orange to the Great Fish and Sundays rivers in the eastern Cape, by more than 1500x 106m3y-’. On the other hand, the ultimate transfer of ca 70 m3s - l will double the yield of the Vaal Basin (already augmented from nine other basins, but the Tugela in particular; see Figure 3, scheme l), and should substantially improve the water quality of the already greatly stressed Vaal (Davies et al., in press). However, it has been suggested by Quibell et al. (1988) that the transfer of clear water from the LHWP to the very turbid Vaal may increase algal growth in the Vaal; this would necessitate new management strategies for the Vaal Dam, in order t o maintain high turbidities. A rapid ‘environmental’ impact study, commissioned by the Lesotho Highlands Development Authority, was conducted over a number of weeks. This highlighted the need for in-depth studies, but with construction already in hand it is only very recently (December 1991) that a 15-month study has begun to examine the physical, chemical and biological characteristics of the rivers involved, to test a water quality monitoring model which will ultimately allow optimal design and utilization of the scheme, and to assess the potential impact of pest simuliid species (Lesotho Highlands Water Project, 1992). Because of this somewhat tardy reaction, no public statement has yet been made regarding potential ecological impacts, and we are left to surmise. Apart from the possibility of biotic transfers, and water quality, temperature and hydrological

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consequences for both donor and recipient systems, the combined impacts on the Noqoe, Malibamatso, Ash, Caledon, Vaal and Orange rivers will be considerable. For example, since the transfer to the Vaal River will be entirely via the Ash, Phase 111 of the scheme will increase the flow of the Ash by an order of magnitude, with major implications for channel integrity and ecological functioning. Abstraction from the Orange through the LHWP on such a scale is all the more serious in the light of recent commitmencs by South Africa to supply Namibia with water from the Lower Orange River.

WATER TRANSFERS IN AUSTRALIA The problem

Australia is a dry continent (Figure 2), because its relatively small land area (8.42 x lo6 km2) lies between latitudes 15"-35" S. As such it is dominated by sub-tropical high pressure cells with a low moisture content. Furthermore, only 7% of the land area lies above 600 m AMSL, so that the MAP is 420 mm, of which only ca 50 mm is converted into runoff (Figure 2). These figures are low, compared with world averages of 660 mm for precipitation and 250 mm for runoff. However, average values are of little real use because marked fluctuations make the country one of the hydrological extremes on a world scale (e.g. Finlayson and McMahon, 1988). The water resource imbalance of the continent is reflected in marked variations in runoff. Ratios of maximum to minimum streamflow (an index of flow variability) range from 6 to > 11 OOOvery large in comparison with Europe (3-10) and North America (3-15). Annual variability reaches a maximum in the arid and semi-arid regions. Spatial variations also are notable; annual runoff for various regions ranges from > 3500 mm in coastal areas, to less than 12.5 mm for more than 75% of the continent! The greatest proportion of the total runoff occurs in the northern and north-eastern coastal areas, with 88% of the total annual runoff coming from only 26% of the land area. Thus, the location of water resources and their availability relative to agricultural and industrial resources and population concentrations is of great concern (Pigram, 1986). Given this variable supply and distribution, IBTs become attractive development options. There are 24 major IBTs supplying water for urban and irrigation purposes, as well as for hydro-electric power generation. The majority involve diversion of coastal rivers along the eastern seaboard, inland to the Murray-Darling Basin, and with increased agricultural production in the basin further developments can be expected (Pigram, 1986). Studies by the New South Wales Water Resources Commission have revealed 40 possible schemes for future IBTs to inland basins in that state alone (Rankine and Hill Pty Limited, 1981). Case history: River Murray transfers

The largest IBTs in Australia involve the import and export of water to and from the Murray-Darling Basin and exceed 2463 x 106 m3 yr- There are three main transfers, the largest being the Snowy Mountains scheme (Figure 6A), a headwater transfer that diverts water from the south-flowing Snowy River into the upper Murray and Murrumbidgee rivers, which flow west. In the mid reaches of the Murray, there are three smaller transfers which divert within the basin for irrigation purposes (Figure 6B). Water is also transferred to the headwaters of a number of basins in the Adelaide/Whyalla region (Figure 6C) from the lowland reaches of the River Murray in South Australia. The Snowy Mountain scheme evolved from the Commonwealth Government's right to develop the water resources of the Snowy River for power generation for Canberra, the Federal capital city. This right was finally exercised in 1949 with the support of the Victorian and New South Wales State Governments. The scheme, built between 1949 and 1974, embraces an area of ca 7000 km2 and involves 15 major dams, many smaller diversion structures, 150 km of tunnels, seven power stations, a pumping station, and 80 km of aqueducts, all at a cost of A$800million.

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The scheme has two broad sections: the northern Snowy-Tumut Development and the southern SnowyMurray Development. Both are connected via tunnels to the main regulating storage, Lake Eucumbene (4800 x lo6 m3) on the Eucumbene River, a tributary of the Snowy River. The Snowy-Tumut transfer involves the diversion of the Eucumbene, the upper Murrumbidgee and the Tooma rivers to the Tumut River, and allows 2.18 x lo6KW hydro-power generation at four power stations, before release into the Murrumbidgee. A tunnel runs through the Great Dividing Range, connecting Lake Eucumbene with the Tumut Pond Reservoir, and hence with the Tumut River, During high flows in the Tumut and Tooma rivers, water in excess of that required for power generation is diverted back through the tunnel to Lake Eucumbene for storage. This section of the scheme provides an extra 1 3 8 0 106m3 ~ yr-’ to the Murrumbidgee, which is sufficient to irrigate an extra 240 000 ha, with an estimated increase in production of A$60 million. The Snowy-Murray transfer diverts water from the Upper Snowy River via a tunnel to the Geehi River, a tributary of the River Murray. Water passing through the tunnel falls ca 820 m, generating a total of 1 . 5 6 106KW ~ at three power stations. Again, a two-way flow connects the Snowy River and Lake Eucumbene, and when Snowy and Geehi river flows exceed the capacity of the Murray power stations, water from the Snowy River is diverted into the lake for storage. Low flows in the Snowy and Geehi are supplemented with water from Lake Eucumbene back through the tunnel, delivering it to the IBT tunnel which connects with the Murray River west of the Great Dividing Range. Additional water is supplied to this transfer from a reservoir further down the Snowy at Jindabyne (668 x lo6m3).This IBT provides an additional 980 x lo6 m3 yr- to the Murray River. Water is transferred to the headwaters of eight catchments in the Adelaide/Whyalla region from the lower reaches of the River Murray in South Australia. The infrastructure is complex (Figure 6C), involving 15 dams, 48 pumping stations, 120 holding tanks and over 1000 km of pipeline. On average, 40% of Adelaide’s annual water supply comes via the Swan Reach, Mannum and Murray Bridge pipeline systems, constructed between 1940 and 1973. During low rainfall years and in summer, these transfers can contribute up to 83% of Adelaide’s total water supply of 190x 106m3yr-l (Figure 7). Three local IBTs, the Mulwala, Yarrawonga and National Channels (Figure 6B) were constructed between 1939 and 1955 for irrigation purposes. Their combined capacity is 5.98 x 106 m3yr- I , with an undetermined quantity returning to the Murray, some 300-500 km downstream. Few studies deal with the impact of IBTs in Australia, and the Snowy Mountains Scheme was completed before environmental impact statements were required. Studies that have been completed are mostly student projects or local government reports, but they d o provide some indication of the possible impacts of IBTs, both on donor and recipient systems. The Snowy Mountain scheme has caused flow reductions in the donor-the Snowy River; all of the flow above Jindabyne is diverted out of the basin, and although this only represents 15% of the catchment area, it represents 50% of the total catchment output. Mean monthly and annual runoff has decreased significantly at all stations, but the magnitude of the reduction decreases with distance downstream (98.8% -44.6%) (Terrazolo, 1990); similar changes to flow duration and flood frequencies have also occurred. The reservoir storage capacities are so large that spills from the lowest dam have occurred in only seven of the last 288 months, and as a result of the diversions, concern has been expressed about the progressive upstream movement of the salt wedge in the lower reaches of the Snowy River. Furthermore, suspended sediment yields immediately below the lowest dam on the Snowy River decreased by 85% after closure of the first dam, and then by a further 99% after completion of the scheme (Terrazolo, 1990). These combined changes in sediment and flow regimes have led to corresponding channel adjustments. Below the main storages, the channel has aggraded and contracted by up to 20% in places, as a result of the introduction of fine tributary sediments and where Salix babylonica and S. viminalis have invaded the channel bed. Loss and/or modification of instream habitat will inevitably occur in donor systems with changes in flow, sediment transport and channel morphology. For example, aquatic insects colonizing the gravel substratum


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WATER SOURCES for the ADELAIDE METROPOLITAN AREA

GROUNDWATER

WINTER MONTHS (May -October)

SUMMER MONTHS (November -April)

GROUNDWATER 12%

Figure 7. Water sources for the Adelaide Metropolitan Area.

of the Snowy River will be influenced by the accumulation of fine tributary sediments on the river bed. Studies by Doeg et 41. (1987) in gravel-bed streams of south-east Australia, have indicated that increased levels of fine sediment, due to catchment modification, have reduced the abundance of Trichoptera, Diptera, Plecoptera and Ephemeroptera. Increased levels of fine sediment fill the interstitial pores between the gravel clasts, reducing habitat space, as well as the dissolved oxygen content of interstitial water. Recent studies by the Victorian Department of Water Resources graded the condition of all the states’ waterways on the basis of 10 factors, including substratum composition, channel stability, water quality and instream biota. The Snowy River was classed as being in poor or moderate condition throughout 95% of its length, while neighbouring tributaries were all considered to be in excellent condition. This apparent decline of the Snowy River primarily appears to be associated with the change in flow conditions due to the IBT (Mitchell, 1990). Recipient systems in the Snowy Mountains Scheme are primarily managed as conduits for irrigation water. For example, the Tumut River is intensively managed to maximize capacity; channel sections are engineered to minimize flow resistance and, as a consequence, all in-channel vegetation is removed. During the summer irrigation period, flows are maintained at bankfull capacity, which has important implications for channel stability (Thorns and Walker, 1992a).

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The Lower Murray transfers have increased both salinity and turbidity of all receiving waters in the Adelaide/Whyalla region (Cugley, 1988), and the cost of salt damage to the Adelaide consumer is estimated at A$20 million yr- I , which corresponds to A$0.70 for every litre of water pumped through the system. The environmental impact of increased salinity levels on the biota of the receiving streams has not been addressed. However, the influence of elevated turbidity levels on recipient systems has been studied by Cugley (1988). Time series analysis of data for the period 1948-86 has indicated that in Mount Bold, one of the larger storages in the Adelaide region, turbidities increased by 15ONTU (Nephelometric Turbidity Units) with the onset of pumping Murray water, and that elevated levels persisted for up to 4 months after the pumping ceased. The ecological impact of increased turbidity, although well documented in the literature (e.g. Bruton, 1985), is unknown for these freshwater systems. However, it has been noted by Cugley (1988) that water transferred from the Murray has elevated nutrient levels, and that this has been associated with an increase in blooms of toxic blue-green algae in Adelaide water storages over the past 10-15 years. Semi-arid fluvial systems typically are highly variable, but this may be suppressed by flow regulation and/or the transfer of water. In particular, disturbance by flooding is a vital factor in the environmental integrity of these, and other, freshwater systems (Davies et al., in press). Floods periodically ‘reset’ ecosystem processes by promoting recruitment of fauna and flora and exchanges between the river and its floodplain. Prior to regulation and the transfer of water, the flow regime of the systems outlined above mirrored the variable semi-arid climate. The river channel and floodplain morphology were configured to accommodate variable flows, and the plants and animals were adapted to such variation. A more stable regime is now imposed by regulation and IBTs (e.g. Thoms and Walker, 1992b; Davies et al., in press) and, therefore, these fluvial ecosystems are undergoing a series of compensatory adjustments. In the Murray, some native species are adapting to the new regime while others, probably the majority, are in decline (Walker, 1992), This may be the ultimate scenario for all aridlsemi-arid systems subject to flow regulation and to IBTs. In Australia, the regulation of surface waters is required to meet consumer demands. To date this has been accomplished through the construction of dams and the impoundment of water. However, with many of the preferred dam sites already utilized, IBTs will become even more common. It is only hoped that studies on the environmental/ecological impacts of such schemes will also proliferate.

WATER TRANSFERS IN THE UNITED STATES Background

The average annual rainfall in the United States is about 760 mm (Foxworthy and Moody, 1986), but the distribution of precipitation is uneven. The eastern part of the country (east of 100” longitude) and the north-west coast receive average annual precipitation > 1120mm, whereas the Great Plains and south-western United States receive < 100 mm. In addition to low average precipitation, the Great Plains and the southwest (away from mountain ranges) have an average annual runoff of only 30mm or less. Like many arid regions of the world, growth and development of the drier sections of the western United States have relied heavily on water transfers to meet growing demands. Estimates indicate that one person in three in the western United States is served by a system that imports water from 160 km away, or more (Biswas, 1979). Water transfer in this area is not a new idea; from 3 0 0 to ~ ~145oAD, native Americans in central Arizona constructed more than 2000 km of canals in what is now the metropolitan Phoenix area (Marsh and Minckley, 1982). While these may not have been true IBTs, the canals certainly set a precedent for the development of large-scale projects that followed (Warnick, 1969). Water transfer in the United States has not been limited to the West. To support the population of metropolitan New York, water was diverted from the Delaware River Basin via a pipeline constructed in 1936 (Howe and Easter, 1971). Inter-basin transfers have also been proposed for Florida (Massarelli and Hannah, 1983), Connecticut (Fattarusso, 1982) and Virginia (Cox and Shabman, 1982). Although distances


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covered by IBTs in the eastern United States are not as great as those in the west, they have played an important role in the urban growth and development of the Atlantic Coast. Case histories

To illustrate some of the complexities of engineering, politics and environmental issues, two case histories are detailed: the California State Water Project and the Garrison Diversion Project (North Dakota). A brief history of each project is presented as well as the important ecological concerns related to the transfer of water. The California State Water Project California has a keen interest in IBTs because ca 70% of the State’s total precipitation occurs in the northern third of the State, whereas > 80% of the water demand is located in the semi-arid southern twothirds (California Department of Water Resources, 1983). Average annual precipitation in California ranges from > lo00 mm along the north coast to < 50 mm in the southern deserts (California Department of Water Resources, 1983). In addition, the precipitation occurs predominantly during winter, whereas demand is greatest in summer. Proposals to carry water from the Sacramento Valley in the north to the San Joaquin Valley in central California began as early as 1873 (Howe and Easter, 1971), but the first IBT to be constructed in California was the 393 km Los Angeles Aqueduct. Completed in 1913, it carries water from Owens Lake to the city of Los Angeles (Figure 8). Other IBTs to southern California and the San Joaquin Valley include the Colorado River Aqueduct, the Delta Mendota Canal of the Central Valley Project (CVP), and the California Aqueduct of the California State Water Project (CSWP). The 389 km Colorado River Aqueduct was completed in 1941, moving water from the Colorado River at the Arizona border to the metropolitan Los Angeles area (California Department of Water Resources, 1983). Inter-basin transfers to the San Joaquin Valley in central California began in 1951 with completion of the 187 km Delta Mendota Canal of the CVP (California Department of Water Resources, 1983). This IBT from the Sacramento-San Joaquin Delta was primarily for agricultural development. In 1968, the CSWP began delivering water from the Sacramento-San Joaquin Delta to agricultural lands in the San Joaquin Valley and in 1972, the California Aqueduct extended 714 km to the Los Angeles area (California Department of Water Resources, 1988). Groundwater overdraft in the San Joaquin Valley and the ever-growing demand for water in southern California were the primary reasons for the construction of the CSWP-one of the most complex IBTs ever constructed, and an impressive feat of technology and engineering. Owen (1975) reported that ApoIlo astronauts could identify only two major structures when looking down on earth-one was the Great Wall of China and the other was the main aqueduct of the CSWP! It pumps water from a forebay in the southern Sacramento-San Joaquin Delta to the San Joaquin Valley agricultural and urban area via the California Aqueduct (Figure 8), and raises the water more than 1 km in elevation over the Tehachapi Mountains. The water pumped by the CSWP originates either as storage from Lake Oroville on the Feather River, or from surplus flows in the Delta. The present dependable supply is ca 2.8 x lo9m3 yr- (California Department of Water Resources, 1987), of which about half goes to southern California, accounting for about onethird of the water use of the region (California Department of Water Resources, 1987). This water is critically important to the second largest urban area in the United States, Los Angeles, as well as the second largest city in California, San Diego. Fresh water flowing into the Sacramento-San Joaquin Delta mixes with denser salt water intruding from the Pacific Ocean, forming a salinity gradient about 80 km long that extends from the western part of the Delta downstream to northern San Francisco Bay. Salinity in the Delta varies spatially and temporally, depending on tidal action, freshwater inflows and pumping rates. During dry years, the combined

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r

1200

115"

I

I

OREGON CALIFORNIA

40

3:

Figure 8. Inter-basin water transfers in California. (Adapted from Ortolano, 1979).

removal of water by both the CSWP and CVP diverts more than half of the annual fresh water inflow to the Delta (California Department of Water Resources, 1987). The CSWP has been the subject of debate over potential adverse environmental effects that it may cause (Ortolano, 1979). Among the concerns are the effects of reduced flows through the Delta and San Francisco


34 1

Bay, and concomitant changes in their ecology. Flow and salinity changes have led to losses of aquatic resources, particularly the striped bass (Morone saxatilis) fishery (Vaux, 1988). Environmental effects of the CSWP (and the CVP) are the subject of California Bay-Delta Proceedings, a series of public meetings held to re-evaluate flow and water-quality requirements of the San Francisco Bay/Sacramento-San Joaquin Delta. This medium-term public process began in 1987 and is scheduled to end in 1993 with a plan to allocate Delta waters in a fashion which will balance the protection afforded the various competing beneficial uses (California State Water Resources Control Board, 1991). Striped bass is one of the most highly sought sportfish in California. In spring, adults spawn in fresh water, primarily in the Delta and in the Sacramento River, while the Delta is the primary nursery area. However, the populations of the Delta have steadily declined due to a variety of factors including changes in flow resulting from IBTs (Stevens et af., 1985). Unfortunately, many adult striped bass have followed enhanced, diverted flows during spawning migrations, leading them to unsuitable areas for spawning, rather than the lesser flows to traditional spawning areas (Stevens and Chadwick, 1979). In addition, diversion of water from the Delta has contributed to the long-term decline of the fish through entrainment of large numbers of young, as well as suppression of their phytoplankton food supply (Stevens et al., 1985; Nichols et al., 1986). Chinook salmon, Oncorhynchus tshawytscha, also use the Delta for migration and as a nursery, with spring and autumn spawning runs supporting extensive sport and commercial fisheries, Spring-run chinook have an unusual life history in that they move to their spawning streams in the spring, hold in deep freshwater pools all summer, and then spawn in autumn. Populations of spring-run chinook in the Sacramento-San Joaquin drainage have recently declined dramatically, perhaps due to flow fluctuations due to IBTs (Campbell and Moyle, 1990). Management actions that could mitigate such effects of IBTs on the fisheries include the maintenance of sufficient freshwater flows to the Pacific Ocean. Water rights issued for both the CSWP and CVP during the late 1970s mandated curtailment of transfers in certain months in order to protect the fishery, and the maintenance of sufficient water to protect the Delta environment (California Department of Water Resources, 1987). However, these measures have not provided sufficient protection, for the Delta fisheries continue to decline. In 1986, the US Bureau of Reclamation and the California Department of Water Resources agreed to improve the coordination of their operations, both to meet water supply and environmental requirements. Increasing human populations, combined with several years of drought, have led to low water-storage levels in California, such that even with the combined IBTs of the Owens Valley, Colorado River, the CVP and the CSWP, the State will be unable to sustain historically prevailing rates of water use (Vaux, 1988), and as the population and economy of southern California continue to grow, the inevitable rise in water demand will have to be met from increasingly distant sources, thereby extending environmental/ecological concerns across an ever-widening area. However, the costs of additional water projects continue to escalate, while competition for remaining supplies required to support human growth and to preserve environmental quality has intensified (and will continue to do so). Thus, the future water demands of a// sectors in California require compromise, and must include a variety of facilities, carefully consider conservation needs, involve water reclamation together with the conjunctive use of surface and groundwater resources, the careful planning of new IBTs, and the development of cost-effective desalination techniques (California State Water Resources Control Board, 1991). The Garrison Diversion Project (North Dakota) The Garrison Diversion Project (GDP) in North Dakota affects parts of the Missouri River and Hudson Bay drainage basins of North Dakota, Minnesota and Canada (Figure 9). Unlike the situation in southern California, this area is predominantly rural, with an estimated human population < 650 000. About 74% of the region is agricultural, with principal crops of wheat, sugar beet, potatoes, corn and other vegetables.

342

102'

98" 1

I

50

MANITOBA

4f

Figure 9. Location of the Garrison Diversion Project.


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The average annual precipitation of the area ranges from ca430-660mm (1951-80), but is often insufficient to support long-term agricultural development. Precipitation varies enormously, both spatially and temporally, with significant wet and dry periods occurring over time scales ranging between 1 and 10 years, causing marked fluctuations in the average annual runoff during such cyclic events. Because of this natural variability, plans were developed to ensure dependable supplies of relatively inexpensive irrigation water, which it was hoped would more than compensate for the equivalent losses of arable land due to the construction of the appropriate water resources project. Thus, the US Congress authorized the development of the GDP in 1965, as an equitable exchange for loss of arable lands, as well as a source of inexpensive hydro-power for economic growth and the relocation of industry to the area (Feldman, 1991). The GDP is one of the largest and most expensive public works projects ever undertaken in the United States of America, and was originally designed to divert water from Lake Sakakawea on the Missouri River above the Garrison Dam, through the McCluskey Canal, to provide irrigation for agriculture in the Hudson Bay drainage area (Figure 9). A series of canals were to convey water to irrigation areas in the Souris and Sheyenne basins, with return flows to Lake Winnipeg in Canada. When completed, the project would comprise a canal system > 4740 km long, with drains and pipelines, delivering 1.1 x lo9m3 yr- (Feldman, 1991)-a truly enormous project. In 1986, after the passage of the 1965 Act, the US Congress passed the Garrison Diversion Project Reformulation Act, which scaled down the GDP, and which shifted the focus away from irrigation towards municipal, fish and wildlife, and recreational uses. Accordingly, the objectives of the GDP became: 1. provision of water for municipal, rural, and industrial use; 2. the irrigation of ca 130 OOO acres of arable land in North Dakota (down from the originally proposed 250000 acres), and 3. the enhancement of recreational opportunities.

What makes the GDP fascinating does not concern any aspects of the engineering, scale or technology, but its demonstration in yet another part of the world of the complexities of internationaVinter-state/interprovincial issues relating to IBTs. The US-Canadian International Joint Commission (created by the Boundary Waters Treaty of 1909) was asked by both countries to examine the potential environmental problems of the GDP, and to render an advisory capacity. This resulted in the creation of the International Garrison Diversion Study Board which partitioned potential, and actual, problems associated with the GDP into five categories, each represented by a specialist scientific committee: Water Quality, Water Quantity, Water Use, Engineering Aspects, and Biology. Ecological concerns included: 1. effects on breeding and migratory areas of rare and endangered waterfowl; 2. leaching of soil as a result of irrigation, and its potential for loss of water quality in the Assiniboine, Red, and Souris rivers; 3. potential increases in flood levels and flood frequency in the Red River caused by irrigation return flows, and 4. the greatest ecological concern: that of potential transfers of Missouri River biota into Canadian waters.

Destruction of waterfowl habitat in North Dakota as a result of the GDP has received a great deal of attention. Migrating waterfowl are an international resource, with wetland areas in North Dakota providing breeding and rearing areas for duck species that are hunted in Canada. Thirteen national wildlife refuges in North Dakota, established to protect waterfowl breeding areas, would have been affected under the original GDP plan, and as a result, Manitoba could have lost 2700 hunter man-days and about

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B. R. DAVIES, M. THOMS A N D M. MEADOR

Can$54 000 yr - in hunter-related income (Oetting, 1977). Therefore, a wetland migration programme devised by the US Fish and Wildlife Service will be conducted based on a hectare-for-hectare re-establishment of wetlands in North Dakota, as approved by the Committee. Concern was also expressed that irrigation return flows in the Hudson Bay watershed could contain high concentrations of dissolved solids, sulphate, sodium, total phosphorus and nitrate-N. If irrigation did occur along the Souris River, dissolved solids concentrations were predicted to increase by an average of 58’70, hardness by 71% and total phosphorus by 159% (Oetting, 1977). Although these concentrations could be handled by existing water treatment facilities, they probably could not treat the expected increased concentrations of sodium, nitrate and sulphate. Expansion of present treatment facilities would cost ca CanSl.9 million yr-l. However, the Water Quality Committee recommended that dissolved solids concentrations in return flows could be decreased by avoiding irrigation of Class A soils along the Souris River, and by the installation of an impervious lining along parts of the Velna Canal. In addition, while flooding was thought to pose major problems (see point 3, above), further examination of flow rates has reduced these concerns. According to the Biology Committee report, at least nine fish species native to the Missouri River or to Lake Sakakawea, but not found in Manitoba, could be expected to invade new environments made available by the GDP. They are the pallid sturgeon Scaphirhynchus albus, the shovelnose sturgeon S. platorhynchus, paddlefish Polyodon spathula, shortnose gar Lepisosteous platostomus, gizzard shad Dorosoma cepedianum, rainbow smelt Osmerus mordax, river carpsucker Carpiodes carpio, smallmouth buffalo Ictiobus bubalus and the Utah chub Gila atraria. The Biology Committee concluded that populations of three species in particular, the Utah chub, gizzard shad and rainbow smelt, could be expected to increase greatly in lakes Manitoba and Winnipeg, to the detriment of walleye Stizostedion vitreum, sauger S . canadense, whitefish Coregonus clupeaformis, and other commercial and sportfish species. When exotic populations become established, walleye, whitefish and sauger populations may disappear, possibly bringing about the total collapse of the commercial fisheries in the two lakes (Keys, 1984). To allay concerns of the Canadian Government over introduced biota, expensive modifications were made. The US Bureau of Reclamation added a fish screen and an extensive sand filtration system to inhibit transfer of biota into the McCIuskey Canal, the critical passage between the Souris and Missouri rivers. However, the International Joint Commission concluded that this did not provide a sufficient guarantee against the introduction of foreign biota (Feldman, 1991). The present status and future of the GDP remains unclear as the Canadian Government is opposed to continued construction of the project until these problems are resolved.

WATER TRANSFER PLANNING: THE NEED FOR AN ECOLOGICAL ETHIC, INTEGRATED CATCHMENT PLANNING, AND FOR MONITORING PROGRAMMES Inter-basin water transfers are already indispensable for the survival of parts of southern AfricaINamibia, Australia and the United States of America, and presumably for many other semi-arid to arid parts of the world (even apparently humid regions-e.g. Canada; Quinn, 1981, and Figure 2). Certainly, for the three regions treated in this paper, IBTs will continue to make even greater contributions to water distribution networks. However, the most disturbing aspects of all IBTs examined in this paper are threefold, namely: 1. In no case has their planning appeared to consider the wider context of integrated catchment management. 2. In no case did initial planning make any contingencies for monitoring impacts. 3. In no case has there been any form of comprehensive, multi-disciplinary, environmental/ecological impact assessment during the planning stages, and in many instances, prior to construction. All of these omissions may be due primarily to the fact that it is only relatively recently that the impacts of IBTs have become apparent, and probably also because both public and planning ‘awareness’ has until


345

now been solely concerned with technical features, and with ‘visual’ (aesthetic) and terrestrial environmental impacts. Early planning has tended to give little or no thought to the continued integrity and functioning of either the donor or the recipient river ecosystems, their estuaries, or to the adjacent marine environments. Certainly, in southern Africa and Australia, the focus has been on construction’site impacts, rather than on the systems as a whole. In terms of biotic and ecosystem conservation, the implications of the hazards inherent in the breakdown of biogeographical barriers should be apparent. These ancient barriers which define lotic ecosystems have led to the development of unique gene pools, many of which we are still ignorant of, and which now are under threat with the advent of IBTs. In South Africa, the introduction of several non-indigenous fish species to the Great Fish River from the Orange River, through the Orange River Project, has been documented (e.g. Jubb, 1976; Cambray and Jubb, 1977; Laurenson and Hocutt, 1984, 1986; Davies et al., in press), even though it was thought impossible, given the nature of the draw-off system. These observations alone serve elegantly to underscore the concerns expressed over potential biotic introductions that the Garrison Diversion Project may cause, and which have been detailed above. Such transfers will have serious repercussions for the natural fish populations of such systems. In the case of invertebrates, not only do many rivers possess endemic faunas, but shifts in the dominance of invertebrate species have already been recorded as the result of altered flow regimes, through IBTs (see e.g. the Great Fish River, South Africa- 500-800’70 increase in flow; seasonal to perenniaVconstant flows: O’Keeffe and De Moor, 1988; Davies et al., in press). Since such shifts in flow regime are common to all IBTs, it is logical to assume that all IBTs will have similar impacts on the biota, with potentially serious implications as far as invasive species and human disease vectors are concerned. Planning and construction of IBTs is not without a host of political, socio-economic, engineering and legal problems (McGauhey, 1969; Weinberg, 1969; Bergman and Matthews, 1983). Despite this, most of these issues have been resolved and many IBTs are currently in operation. However, in most cases, considerations of ecological effects have been of secondary concern during the planning process (Petitjean and Davies, 1988a, b; Meador, 1992; see above). History suggests that the approach to the study of potential environmental impacts of IBTs has been somewhat haphazard, and often reactive rather than proactive. Howe (1985) called for research into IBT designs, stating that ‘. . . timely research on the economic, legal and hydrologic issues involved in interstate water transfers may preclude unnecessary hardening of state policies, obviate litigation, and avoid unnecessary expense and environmental damages of future [water] development.’ The case studies presented here more than indicate a need for research concerning the environmental effects of water transfers; a new ethic is required. Research should address not only a comprehensive approach to measuring the ecological impacts of water transfer, but also the evaluation of the ecological risks associated with IBTs, as well as the development of monitoring programmes which will allow alterations to be made to operational criteria, such that particularly deleterious impacts may be reduced, should this become necessary. This also emphasises the need for flexible design in operational criteria in the first place. The ecological character of natural resources is an important component of water resource development. We cannot alter natural river basins without harm to their ecological balance. Feldman (1991) advocated incorporating ecological considerations in water resources planning as a means of establishing an environmentalethic with respect to water transfers. Leopold (1966) stated that all ethics rest upon the single premise that the individual is a member of a community of interdependent parts (as is any catchment/river basin). Perhaps recognition of ecological and socio-economic aspects of IBTs as interdependent components of water resource development will promote an ecological ethic toward future water transfer projects, thereby minimizing potential ecological impacts. Thomas and Box (1969) stated, ‘. . . We do not argue that this large scale movement of water is not inevitable or unnecessary, but we d o believe that, before further action is taken more careful investigations should be made of the ecological and social implications of water transport. We urge [that] sound ecological

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studies should be incorporated in the initial planning for large-scale water movement.’ Twenty years later, Petitjean and Davies (1988a, b) underscored the lack of knowledge relating to the ecological effects of IBTs, thus: ‘. . . It is imperative that formal ecological impact assessments and research infrastructure be drawn up nationally, as a matter of priority, in order that the deleterious impacts of future transfer schemes be minimised. ’ Forums such as workshops, symposia or other conferences can be appropriate media through which to address research issues related to the role of ecology in the planning of IBTs. In this context, and through the medium of this Journal, we urge that an international workshop be conducted to address the lack of knowledge of the ecological impacts of IBTs, their extent and distribution, and the development of a suitable ecological ethic, monitoring programmes, and the integration of IBTs into overall catchment planning and management. These issues must include appropriate tools and strategies for measuring ecological impacts, the evaluation of the risks of impacts, and the incorporation of ecological concerns into an integrated design for future water transfer projects. ACKNOWLEDGEMENTS

We are grateful to Wynne Henderson who typed a large portion of the manuscript, and to Kate Snaddon for drawing Figures 1-5. Funds for the preparation of this paper were generated through the Foundation for Research Development Core Programme and Special Programme on South African Rivers held by the senior author. We should also like to acknowledge Dr P. Boon of Scottish Natural Heritage, UK, and Dr R. M. Baxter of the National Water Research Institute, Burlington, Ontario, for their most useful and constructive comments on an earlier draft of the paper. Shirley Bethune is warmly thanked for her generous provision of the draft report to the Department of Water Affairs, Republic of Namibia, on the Eastern National Water Carrier. REFERENCES

Alexander, W. J. R. 1985. ‘Hydrology of low-latitude Southern Hemisphere land masses’, in Davies, B. R. and Walmsley, R. D. (Eds), Perspectives in Southern Hemisphere Limnology, Developments in Hydrobiology, 28, Dr W. Junk, Dordrecht , 75 -83. Allanson, B. R., Hart, R. C., O’Keeffe, J. H. and Robarts, R. D. 1990. Inland Waters of Soufhern Africa, Kluwer, Dordrecht. Bailey, R. G. and Cobb, S. M. 1984. ‘A note on some investigations carried out in the area of the Sudan Plain to be affected by the Jonglei Canal’, Hydrobiologia, 110, 45-46. Bergman, A. and Matthews, R. H. 1983. ‘Compensation under interbasin transfers of water-its effect upon regional and state water resources planning’, in Charbeneau, R. J. and Poppkin, B. P. (Eds), Regional and State Water Resources Planning and Management, Proceedings of a Symposium of the American Water Resources Association, Bethesda, Maryland, 153-158. Bethune, S. 1991. ‘Kavango River wetlands’, Madoqua, 17, 77-112. Bethune, S. and Chivell, E. 1985. ‘Environmental aspects of the Eastern National Water Carrier’, South West African Annual, Windhoek, 1985, 23-27. Bethune, S., Puz, A. and Roeis, R. 1984. Changes to Water Quaiity due to Long Distance Transport, Internal Report, Department of Water Affairs, South West AfricaINamibia, Division of Research and Special Investigations, Windhoek. Biswas, A. K. 1979. ‘North American water transfers; an overview,’ in Golubev, G. N. and Biswas, A. K. (Eds), Interregional Water Transfers: Problems and Prospects, Pergamon Press, New York, 79-90. Biswas, A. K., Zuo Dakang Nickum, J. E. and Liu Changming 1983. Long-distance Water Transfer: a Chinese Case Study and International Experiences, United Nations University and Tycooly International Publishing Limited, Dublin. Bruton, M. N. 1985. ‘The effects of suspensoids on fish’, in Davies, B. R. and Walmsley, R. D. (Eds), Perspectives in Southern Hemisphere Limnoiogy, Developments in Hydrobiology, 28, Dr W. Junk, Dordrecht, 221-241. California Department of Water Resources 1983. ‘The California Water Plan: projected use and available water supplies to 2010’, California Department of Water Resources Bulletin, 160-183. California Department of Water Resources 1987. ‘California water: looking to the future’, California Department of Water Resources Bulletin, 160-187. California Department of Water Resources 1988. ‘Management of the California State Water Project’, California Department of Water Resources Bulletin, 132-188.


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California State Water Resources Control Board (CSWRCB) 1991. Water Quality Control Plan for Salinity: Sun Francisco Bay/Sacramento-Sun Joaquin Delta Estuary, Report Number 91-15WR. Cambray J . A. and Jubb, R. A. 1977. ‘Dispersal of fishes via the Orange-Fish Tunnel, South Africa’, Journal of the Limnological Society of southern Africa, 3, 33-35. Campbell, E. A. and Moyle, P. B. 1990. ‘Ecology and Conservation of Spring-run Chinook Salmon: Reversing the Effects of Water Projects’, Technical Completion Report, California Water Resources Center Project Report, UCAL-WRC-W-7 19. Cashman, A., Harris M., Plettenberger, H. and Volkman, B. 1986. Preliminary Reconnaissance Report on Irrigation PossibilitiesAlong the Okavango River in Kavango, Report of the Planning Division, Department of Water Affairs, Windhoek. Chang Ming, L., Dakang, Z. and Yuexian, X. 1985. ‘Water transfer in China: the east route project’, in Golubev, G. N. and Biswas, A. K . (Eds), Large-scale Water Transfers: Emerging Environmental and Social Experiences, United Nations Environmental Programmes, Water Resources Series Vo1.7, Tycooly Publishing, Oxford, 103- 118. Charnock, A. 1983. ‘A new course for the Nile’, New Scientist, Oct. 27, 281-288. Comrie-Greig, J. 1986. ‘The E.N.W.C., ‘‘Killer Canal” or Life-giving Artery, or both?’, African Wildlife, 40, 68-73. Cox, W. E. and Shabman, L. A. 1982. Institutional Issues Affecting Water Supply Development: Illustrations from Southeastern Virginia, Virginia Water Resources Research Center Completion Report, Blacksburg. Craig, J. F. and Kemper, J. V. (Eds) 1987. Regulated Streams: Advances in Ecology, Plenum Press, New York. Critchfield, R. 1978. ‘Crocodiles, cattle and the Jonglei Canal’, International Wildlife, 8 , 20-25. Cugley, J. A. 1988. Time Series Analysis of Turbidity Data from Mt Bold Reservoir in South Australia, South Australian Engineering and Water Department, Ref 88/18. Cummings, R. G. 1974. Inter-basin Water Transfers. A Case Study in Mexico, Resources for the Future, Incorporated. Johns Hopkins Press, Baltimore and London. Davies, B. R. and Day, J. H. 1986. The Biology and Conservation of South Africa’s Vanishing Waters, Department of Extra-Mural Studies, University of Cape Town, and the Western Cape Branch of the Wildlife Society of Southern Africa. Davies, B. R., O’Keeffe, J. H . and Snaddon, C. D. in press. ‘River and stream ecosystems in southern Africa: predictably unpredictable?’, in Cushing, C. E., Cummins, K . W. and Minshall, 0. W. (Eds), River and Stream Ecosystem Paradigms, Elsevier, Amsterdam. Davies, B. R. and Walker, K. F. (Eds) 1986. The Ecology of River Systems, Monographiae Biologicae, 60, Dr W. Junk, Dordrecht. Department of Water Affairs 1985. The Lesotho Highlands Scheme: A Water Supply “Super-Project”, South African Construction World (Johannesburg), Supplement to the Dambuilders: 75 years with the Department of Water Affairs, pp. 24-26, 29, 3 1, Department of Water Affairs, Pretoria. Department of Water Affairs 1986. Management of the Water Resources of the Republic of South Africa, Department of Water Affairs and Forestry, Private Bag X313, Pretoria. Department of Water Affairs, Republic of Namibia 1992. Final Report on the Investigation into the Influence of the Grootjontein-Omatako Canal on Wild Animals and Methods to Prevent Identified Problems, Draft Report WR/91/5, Windhoek. Department of Water Affairs, South Africa, and Department of Agriculture and Nature Conservation, S.W.A./Namibia 1987. Report on the First Phase of the Investigation into the Effects of the Grootfontein-Omatako Canal on Wild Animals, and Methods to Prevent Identified Problems, Department of Water Affairs, Pretoria, Steering Committee, file number 10/12/3/4. Doeg, T. J., Davey, G. W . and Blyth, J. D. 1987. ‘Response of the aquatic macroinvertebrate communities in the Thomson River, South eastern Australia’, Regulated Rivers: Research & Management, 1, 195-210. El-Ashry, M. T. and Gibbons, D. C. 1988. Water and Arid Lands of the Western United States, World Resources Institute. Cambridge University Press, Cambridge. Fattarusso, L. R. 1982. An Economic Evaluation of Interbasin Water Transfers: A Case Study of Southwestern Connecticut, unpublished M.Sc thesis, Connecticut University, Storrs. Feldman, D. T. 1991. Water Resources Management, The Johns Hopkins University Press, Baltimore, Maryland. Finlayson, B. L. and McMahon, T. A. 1988. ‘Australia v the world: A comparative analysis of streamflow characteristics’, in Warner, R. F. (Ed.), Fluvial Geomorphology of Australia, Academic Press, Sydney, 17-40. Foxworthy, B. L. and Moody, D. W. 1986. ‘National perspective on surface-water resources’, in US Geological Survey, National Water Summary 1985, Hydrologic Events and Surface-water Resources, Water-Supply Paper 2300, 5 1-68. Golubev, G. N. and Biswas, A. K . 1979. Interregional Water Transfers, Problems and Prospects, Pergamon Press, Oxford. Golubev, G. N. and Biswas, A. K. 1985. ‘Large-scale water transfers: emerging environmental and social issues’, in Golubev, G. N. and Biswas, A. K. (Eds), Large-scale Water Transfers: Emerging Environmental and Social Experiences, United Nations Environmental Programmes, Water Resources Series Vo1.7, Tycooly Publishing, Oxford, 1-5.

348


Gore, J. A. and Petts, G. E. (Eds) 1989. Alternatives in Regulated River Management, CRC Press, Boca Raton, Florida. Howe, C. W. 1985. ‘Economic, legal, and hydrologic dimensions of interstate water markets’, American Journal of Agricultural Economics, 67, 1226- 123 1. Howe, C. W. and Easter, K. W. 1971. Interbasin Transfers of Water-Economic Issuesand Impacts, The Johns Hopkins University Press, Baltimore, Maryland. Jones, B. 1987. ‘The Eastern National Water Carrier’, African Wildlife, 41, 110-113. Jubb, R. A. 1976. ‘Unintentional introduction of fish via hydroelectric power stations and centrifugal pumps’, Journal of the Limnological Society of southern Africa, 2, 29-30. Keys, D. L. 1984. ‘National environmental policy, foreign policy, and the Garrison Diversion Unit’, The Environmental Professional, 6, 223-234.’ Laurenson, L. J . B. and Hocutt, C. H. 1984. ‘The introduction of the Rock Catfish, Gephyroglanis sclateri into the Great Fish River via the Orange/Fish Tunnel, S.A.’, The Naturalist, 28, 12-15. Laurenson, L. J. B. and Hocutt, C. H. 1986. ‘Colonisation theory and invasive biota: The Great Fish River, a case study’, Environmental Monitoring and Assessment, 6, 71-91. Leopold, A., 1966. A Sand County Almanac, Oxford University Press, New York. Lesotho Highlands Water Project. 1992. ‘WATERTEK obtains contract for water study’, WATERTEKNewsIetter, 6, 1. Lillehammer, A. and Saltveit, S. J. (Eds) 1984. Regulated Rivers, Universitetsforlaget AS, Oslo. Marsh, P. C. and Minckley, W. L. 1982. ‘Fishes of the Phoenix metropolitan area in central Arizona’, North American Journal of Fisheries Management, 2 , 395-402. Massarelli, R. J. and Hannah, J. W. 1983. ‘Caught in the middle-interbasin transfer of water from a local government perspective’, in Charbeneau, R. J. and Popkin, B. P. (Eds), Regional and State Water Resources Planning and Management,Proceedings of a Symposium of the American Water Resources Association, Bethesda, Maryland, 147- 152. McGauhey, P. H., 1969. ‘Physical implications of large scale water transfers’, in Bagley, J . M. and Smiley, T. L. (Eds), Arid Lands in Perspective, University of Arizona Press, Tucson, 358-374. Meador, M. R. 1992. ‘Inter-basin water transfers: ecological concerns’, Fisheries (Bethesda), 17, 17-22. Mitchell, P. 1990. The Environmental Condition of Victorian Streams, Department of Water Resources, Victoria. Nichols, F. H., Cloern, J. E., Luoma, S. N. and Peterson, D. H. 1986. ‘The modification of an estuary’, Science, 231, 567-573.

Oetting, R. E. 1977. ‘How the Garrison Dam Project affects Canada’, Canadian Geographic Journal, October/November. 38-45.

O’Keeffe, J. H . and De Moor, F. C. 1988. ‘Changes in the physico-chemistry and benthic invertebrates of the Great Fish River, South Africa, following an interbasin transfer of water’, Regulated Rivers: Research & Management, 2, 39-55.

O’Keeffe, J . H., Palmer, R. W., Byren, B. A. and Davies, B. R. 1990. ‘The effects of impoundment on the physicochemistry of two contrasting southern African river systems’, Regulated Rivers: Research & Management, 5,97- 110. Ortolano, L. 1979. ‘Environmental assessments in water resources planning’, in Golubev, G. N. and Biswas, A. K. (Eds), Interregional Water Transfers: Problems and Prospects, Pergamon Press, New York, 159- 176. Owen, 0. S., 1975. Natural Resources Conservation: An Ecological Approach, MacMillan, New York. Petitjean, M. 0. G. and Davies, B. R. 1988a. A Review ofthe Ecological and Environmental Impacts of Inter-basin Water Transfer Schemes in southern Africa: Synthesis (Part I) and International Bibliography (Part 11), Foundation for Research Development, Council for Scientific and Industrial Research, Pretoria, and Freshwater Research Unit, University of Cape Town, Occasional Report 38. Petitjean, M. 0. G . and Davies, B. R. 1988b. ‘Ecological impacts of inter-basin water transfers: some case studies, research requirements and assessment procedures in southern Africa’, South African Journal ofscience, 84,819-828. Petts, G . E. 1984. Impounded Rivers, John Wiley, Chichester. Pigram, J. J. 1986. Issues in the Management of Australia’s Water Resources, Longman Cheshire, Melbourne. Quibell, G., Howard, M. and Bruwer, C. 1988. TheMovement ofLess Turbid Water Plumes in the Vaal Dam-Some Management Options, Department of Water Affairs, South Africa, Internal Report Number N/C800/Ol/DEQ/11/88, Pretoria. Quinn, F. J. 1981. ‘Water transfers-Canadian style’, Canadian Water Resources Journal, 6, 64-76. Rankine and Hill Pty Limited 1981. Possibilities of Inland Diversion of N.S. W. Coastal Streams, Water Resources Commission of New South Wales, Sydney. Ravenscroft, W . , Bethune, S . and Chivell, E. 1985. ‘The Eastern National Water Carrier-assuaging a nation’s thirst’, South West African Annals, 1985, South West Africa Publications, Windhoek. Skelton, P. H. and Merron, G. S. 1985. Possible Impacts ofthe E.N. W.C.on Fish, J. L. B. Smith Institute of Ichthyology, Grahamstown, Investigational Report 14. Stevens, D. E. and Chadwick, H . K. 1979. ‘Sacramento-San Joaquin estuary- biology and hydrology’, Fisheries (Bethesda), 4, 2-6.


349

Stevens, D. E., Kohlhorst, D. W., Miller, L. W. and Kelley, D. W. 1985. ‘The decline of striped bass in the SacramentoSan Joaquin estuary, California’, Transactions of the American Fisheries Society, 114, 12-30. Terrazolo, N. 1990. Hydrogeomorphic Impacts of the Snowy Mountains Hydroelectric Scheme on the Snowy River, Unpublished B.Sc thesis, University of New South Wales. Thomas, G. W. and Box, T. W. 1969. ‘Social and ecological implications of water importation into arid lands’, in Bagley, J. M. and Smiley, T. L. (Eds), Arid Lands in Perspective, University of Arizona Press, Tucson, 363-374. Thoms, M. C. and Walker, K. F. 1992a. ‘Sediment transport in a regulated semi-arid river: The River Murray, Australia’, in Robarts, R. D. and Bothwell, M. L. (Eds), Aquatic Ecosystems in Semi-arid Regions: Implications for Resource Management, Environment Canada, Saaskatoon, NHRI Symposium Series 1, 239-250. Thoms, M. C. and Walker, K. F. 1992b. ‘Channel changes related to low level weirs on the River Murray, Australia’, in Carling, P. A. and Petts, G.E. (Eds), Lowland Floodplain Rivers: Geomorphological Perspectives, John Wiley, Chichester, 235-249. Vannote, R. L., Minshall, 0.W., Cummins, K. W., Sedell, J. W. and Cushing, C. E. 1980. ‘The River Continuum Concept’, Canadian Journal of Fisheries and Aquatic Sciences, 37, 130- 137. Vaux, H. J., Jr. 1988. ‘Growth and water in the South Coast Basin of California’, in El-Ashry, M. T. and Gibbons, D. C. (Eds), Water and Arid Lands of the Western United Stales, Cambridge University Press, New York, 233-279. Voropaev, G.V. and Velikanov, A. L. 1985. ‘Partial southward diversion of northern and Siberian rivers’, in Golubev, G. N. and Biswas, A. K. (Eds), Large-scale Water Transfers:Emerging Environmental and Social Experiences, United Nations Environmental Programmes, Water Resources Series Vo1.7, Tycooly Publishing, Oxford, 67-83. Walker, K. F. 1992. ‘A semi-arid lowland river: The River Murray, Australia’, in Calow, P. and Petts, G.E. (Eds) The Rivers Handbook, Vol. 1, Blackwell Scientific, Oxford. Ward, J. V. and Stanford, J. A. (Eds)’l979. The Ecology of Regulated Streams, Plenum Press, New York. Ward, J. V. and Stanford, J. A. 1983. ‘The Serial Discontinuity Concept of lotic ecosystems’, in Fontaine, T. D. and Bartell, S. M. (Eds), Dynamics of Lotic Ecosystems, Ann Arbor Science Publishers, Michigan, 29-42. Warnick, C. C. 1969. ‘Historical background and philosophical basis of regional water transfer’, in Bagley, J . M. and Smiley, T. L. (Eds), Arid Lands in Perspective, University of Arizona Press, Tucson, 358-374. Weinberg, E. 1969. ‘Intrastate, interstate, and international legal and administrative problems of large-scale water transfer’, in Bagley, J. M. and Smiley, T. L. (Eds), Arid Lands in Perspective, University of Arizona Press, Tucson, 352-357.