26326 Water Resources and Environment Technical Note G.2 Lake Management Series Editors Richard Davis Rafik Hirji WATER RESOURCES AND ENVIRONMENT TECHNICAL NOTE G.2 Lake Management SERIES EDITORS RICHARD DAVIS, RAFIK HIRJI The World Bank Washington, D.C. Water Resources and Environment Technical Notes A. Environmental Issues and Lessons Note A.1 Environmental Aspects of Water Resources Management Note A.2 Water Resources Management Policy Implementation: Early Lessons B. Institutional and Regulatory Issues Note B.1 Strategic Environmental Assessment: A Watershed Approach Note B.2 Water Resources Management: Regulatory Dimensions Note B.3 Regulations for Private Sector Utilities C. Environmental Flow Assessment Note C.1 Environmental Flows: Concepts and Methods Note C.2 Environmental Flows: Case Studies Note C.3 Environmental Flows: Flood Flows Note C.4 Environmental Flows: Social Issues D. Water Quality Management Note D.1 Water Quality: Assessment and Protection Note D.2 Water Quality: Wastewater Treatment Note D.3 Water Quality: Nonpoint-Source Pollution E. Irrigation and Drainage Note E.1 Irrigation and Drainage: Development Note E.2 Irrigation and Drainage: Rehabilitation F. Water Conservation and Demand Management Note F.1 Water Conservation: Urban Utilities Note F.2 Water Conservation: Irrigation Note F.3 Wastewater Reuse G. Waterbody Management Note G.1 Groundwater Management Note G.2 Lake Management Note G.3 Wetlands Management Note G.4 Management of Aquatic Plants H. Selected Topics Note H.1 Interbasin Transfers Note H.2 Desalination Note H.3 Climate Variability and Climate Change Copyright © 2003 The International Bank for Reconstruction and Development/THE WORLD BANK 1818 H Street, N.W., Washington, D.C. 20433, U.S.A. All rights reserved. Manufactured in the United States of America First printing March 2003 2 CONTENTS Foreword 5 Acknowledgments 7 Introduction 8 Valuing Lakes and Reservoirs 9 Lakes not only provide the most easily accessible source of freshwater for humans but also provide a habitat for much of the planet's aquatic biological diversity. Mistakes in the management of lakes can have catastrophic consequences for ecosystem in- Author tegrity and human development. Lawrence Mee How Lakes Function 9 Technical Adviser Lakes exhibit a complex interaction among physical, Stephen Lintner chemical, and biological processes. Human interven- tions are modifying all three of these drivers, so it is not Editor surprising that the service functions and ecology of Robert Livernash lakes are sometimes severely compromised. Production Staff Cover Design: Cathe Fadel Human Disturbance of Lakes 14 Human development of catchments has often included Design and Production: the use of rivers and lakes as receptacles of pollut- The Word Express, Inc. ants from industry, agriculture, and domestic sources. Excessive water withdrawals, exotic biota, and over- Notes fishing also threaten the integrity of lakes. Unless otherwise stated, all dollars = U.S. dollars. Policy Approaches for Improving Lake Management 18 All tons are metric tons. Modern policy approaches are needed to ensure that The boundaries, colors, the management of lakes and reservoirs is sustainable. denominations, and any They include sectoral cooperation and joint planning, other information shown on any stakeholder participation, and the application of eco- maps do not imply, nomic instruments. on the part of the World Bank Group, any judgment on the legal Tools for Remedial Action 24 status of any territory, or any As a general rule, it is more cost-effective to control endorsement or acceptance of problems at their source than to undertake remedial such boundaries. action. Nevertheless, remedial approaches are some- times unavoidable. Cover photo by Curt Carnemark, World Bank Fisherman, Indonesia Future Challenges 27 At a global level, there is a major challenge in man- This series also is available on the aging lake waters to simultaneously feed the hungry World Bank website while maintaining economic productivity and environ- (www.worldbank.org). mental health. Further Information 28 3 WATER RESOURCESANDENVIRONMENT · TECHNICAL NOTE G.2 Tables 1. Transboundary lakes: functions, uses, and threats 10 2. Techniques for controlling algae in eutrophic lakes 25 3. Techniques to control nuisance macrophytes 26 4. Multiple benefit treatments 27 Figures 1. Water quality models 15 2. Trends in phosphorus concentrations in three lakes in Northern Ireland, 16 1850­2000 3. Impact of Nile perch on Haplochromines in Lake Victoria 17 4. Annual fish catch from Kenyan part of Lake Victoria 18 Boxes 1. Factors determining the state of a lake 13 2. Three lakes endangered by pollution 14 3. Some damaging introductions 17 4. Lake Patzcuaro, México 20 5. Integrated catchment management and the Great Lakes 21 6. Development of a coordination mechanism: Chilika Lake, Orissa, India 22 7. Transboundary Lakes in East Africa: Management approaches and 23 the involvement of the GEF 4 LAKE MANAGEMENT FOREWORD The environmentally sustainable development and priority in Bank lending. Many lessons have been management of water resources is a critical and learned, and these have contributed to changing complex issue for both rich and poor countries. It attitudes and practices in World Bank operations. is technically challenging and often entails difficult trade-offs among social, economic, and political con- Water resources management is also a critical de- siderations. Typically, the environment is treated velopment issue because of its many links to pov- as a marginal issue when it is actually key to sus- erty reduction, including health, agricultural tainable water management. productivity, industrial and energy development, and sustainable growth in downstream communi- According to the World Bank's recently approved ties. But strategies to reduce poverty should not lead Water Resources Sector Strategy, "the environment to further degradation of water resources or eco- is a special `water-using sector' in that most envi- logical services. Finding a balance between these ronmental concerns are a central part of overall objectives is an important aspect of the Bank's in- water resources management, and not just a part terest in sustainable development. The 2001 Envi- of a distinct water-using sector" (World Bank 2003: ronment Strategy underscores the linkages among 28). Being integral to overall water resources man- water resources management, environmental agement, the environment is "voiceless" when other sustainability, and poverty, and shows how the 2003 water using sectors have distinct voices. As a con- Water Resources Sector Strategy's call for using sequence, representatives of these other water us- water as a vehicle for increasing growth and re- ing sectors need to be fully aware of the importance ducing poverty can be carried out in a socially and of environmental aspects of water resources man- environmentally responsible manner. agement for the development of their sectoral in- terests. Over the past few decades, many nations have been subjected to the ravages of either droughts or floods. For us in the World Bank, water resources man- Unsustainable land and water use practices have agement--including the development of surface and contributed to the degradation of the water resources groundwater resources for urban, rural, agriculture, base and are undermining the primary investments energy, mining, and industrial uses, as well as the in water supply, energy and irrigation infrastruc- protection of surface and groundwater sources, pol- ture, often also contributing to loss of biodiversity. lution control, watershed management, control of In response, new policy and institutional reforms water weeds, and restoration of degraded ecosys- are being developed to ensure responsible and sus- tems such as lakes and wetlands--is an important tainable practices are put in place, and new predic- element of our lending, supporting one of the es- tive and forecasting techniques are being developed sential building blocks for sustaining livelihoods and that can help to reduce the impacts and manage for social and economic development in general. the consequences of such events. The Environment Prior to 1993, environmental considerations of such and Water Resources Sector Strategies make it clear investments were addressed reactively and prima- that water must be treated as a resource that spans rily through the Bank's safeguard policies. The 1993 multiple uses in a river basin, particularly to main- Water Resources Management Policy Paper broad- tain sufficient flows of sufficient quality at the ap- ened the development focus to include the protec- propriate times to offset upstream abstraction and tion and management of water resources in an pollution and sustain the downstream social, eco- environmentally sustainable, socially acceptable, logical, and hydrological functions of watersheds and economically efficient manner as an emerging and wetlands. 5 WATER RESOURCES ANDENVIRONMENT · TECHNICAL NOTE G.2 With the support of the Government of the Nether- The Notes are in eight categories: environmental lands, the Environment Department has prepared issues and lessons; institutional and regulatory is- an initial series of Water Resources and Environ- sues; environmental flow assessment; water qual- ment Technical Notes to improve the knowledge ity management; irrigation and drainage; water base about applying environmental management conservation (demand management); waterbody principles to water resources management. The management; and selected topics. The series may Technical Note series supports the implementation be expanded in the future to include other relevant of the World Bank 1993 Water Resources Manage- categories or topics. Not all topics will be of inter- ment Policy, 2001 Environment Strategy, and 2003 est to all specialists. Some will find the review of Water Resources Sector Strategy, as well as the past environmental practices in the water sector implementation of the Bank's safeguard policies. useful for learning and improving their perfor- The Notes are also consistent with the Millennium mance; others may find their suggestions for fur- Development Goal objectives related to environmen- ther, more detailed information to be valuable; while tal sustainability of water resources. still others will find them useful as a reference on emerging topics such as environmental flow assess- The Notes are intended for use by those without ment, environmental regulations for private water specific training in water resources management utilities, inter-basin water transfers, and climate such as technical specialists, policymakers and variability and climate change. The latter topics are managers working on water sector related invest- likely to be of increasing importance as the World ments within the Bank; practitioners from bilateral, Bank implements its environment and water re- multilateral, and nongovernmental organizations; sources sector strategies and supports the next gen- and public and private sector specialists interested eration of water resources and environmental policy in environmentally sustainable water resources and institutional reforms. management. These people may have been trained as environmental, municipal, water resources, ir- rigation, power, or mining engineers; or as econo- mists, lawyers, sociologists, natural resources Kristalina Georgieva specialists, urban planners, environmental planners, Director or ecologists. Environment Department 6 LAKE MANAGEMENT ACKNOWLEDGMENTS The production of this Technical Note has been sup- Technical Note G.2 was drafted by Lawrence Mee ported by a trust fund from the Government of the of the International Centre for Water Studies, the Netherlands that is managed by the World Bank. Netherlands. The Note was reviewed by Hans-Olav Ibrekk of the World Bank. 7 WATER RESOURCESAND ENVIRONMENT · TECHNICAL NOTE G.2 INTRODUCTION According to the World Lake Vision (2003) it is es- implementation of more than 10 major lake man- timated that lakes, both natural and manmade, store agement projects, many with support from the Glo- more than 90 percent of the world's surface fresh- bal Environment Facility. In addition, a recently water resources. They are heavily used for a vari- launched GEF Medium Size Project--Towards a Lake ety of human activities, including drinking, fishing, Basin Management Initiative--will review experi- irrigation, navigation, and recreation. As a result of ences of about 28 GEF and non-GEF lake manage- this increased usage, lakes are increasingly threat- ment projects to draw lessons for improving lake ened by abstractions for agriculture, pollution from management investments discharges, and sedimentation from poor land man- agement practices. As natural sinks with longer resi- This Note is one in a series of Water Resources dence times than rivers, lakes are more fragile and and Environment Technical Notes that have been susceptible to degradation from such threats. Un- prepared by the Environment Department to ap- less these threats are reduced through better invest- ply environmental management principles to wa- ment decisions and management practices, humans ter resources management. This Note presents the will lose access to their most readily available source social and economic context of lakes within the of high-quality freshwater. current pattern of human development. It describes how lakes function and the threats to these func- Lake management is an important issue for the tions from human activities. It also examines al- World Bank. The Bank has ternative policy approaches described the problems of to lake management and re- managing and restoring medial measures for se- lakes and reservoirs in Tech- verely damaged lakes, as nical Report 289 (1995) and well as emerging issues and summarized its work in sup- Bank future challenges for lake porting lake management in orld ,W management. Most of the Technical Report 358 (1996). information in this Note is At present, the Bank is sup- Huffman equally applicable to both porting the preparation and Edwin lakes and reservoirs. by Photo Philippines 8 LAKE MANAGEMENT VALUING LAKES AND RESERVOIRS Freshwater constitutes only about 2.5 percent of the diversity. Lakes are the main life support mecha- world's water reserves. Over 99 percent of this fresh- nism for many plant and animal species, as well as water is locked up in groundwater, snow caps, gla- migratory birds. For example, freshwater fish rep- ciers, and permafrost. Our planet's terrestrial resent 25 percent of all known vertebrate animal ecosystems, including the human population, largely species. depend upon the 117,490 km3 of freshwater present in rivers, lakes, and swamps. This critical resource Table 1 illustrates the functions, human uses, and constitutes just 0.0085 percent of the global water major threats to some of the world's key trans- reserve. Over 75 percent of this "easily accessible" boundary lakes. water is found in lakes. RESERVOIRS: THE IMPORTANCE OF LAKES NEW LAKE ENVIRONMENTS Apart from their role in providing drinking water, In the last century, humans have altered the earth's irrigation water, and food supplies, lakes also pro- hydrological cycle by damming rivers to create ar- vide vital service functions, such as controlling tificial reservoirs. There are now 45,000 dams over floods, assimilating plant nutrients, retaining sedi- 15m in height that contain 20 percent of global mean ments, and recharging groundwater. Yet human runoff. These reservoirs are often deep, with steep activities are damaging many lakes and impairing shorelines. They act as lakes at the earliest stages many of these functions. According to the UN's 1997 of their evolution, often with unstable and poorly Comprehensive Assessment of the Freshwater Re- adapted ecosystems. Like lakes, they are filling with sources of the World, the water levels of many lakes sediment. For example, as a result of sedimenta- are declining, and many lakes are severely contami- tion over a period of 25 years, the Tarbela Reser- nated by human, industrial, and agricultural wastes. voir on the Indus River in Pakistan has lost 18 percent of live storage.1 Shallow reservoirs also tend Freshwater is not only vital for human life but pro- to suffer from eutrophication. vides a habitat for much of the planet's biological HOW LAKES FUNCTION Knowing how lakes function from a biophysical per- years ago. But the ages of most lakes can be mea- spective allows managers to understand the threats sured in thousands of years. The entire Great Lakes that lakes face from development, as well as pos- system, for example, was formed less than 10,000 sible ways to minimize those threats. years ago by the retreating ice sheet after the last Ice Age. LIFE CYCLES AND WATER BUDGET The lifetime of lakes is being shortened through wa- All lakes are at some point in a natural process ter abstractions. According to the recent report of that will eventually lead to their extinction. A few the World Commission on Dams, around 3,800 km3 lakes are very old. Lake Baikal, for example, was formed 25 million years ago; Lake Tanganyika, 10 million years ago; and Lake Ohrid, 2 to 3 million 1World Commission on Dams (2000). 9 WATER RESOURCES AND ENVIRONMENT · TECHNICAL NOTE G.2 TABLE 1. TRANSBOUNDARY LAKES : FUNCTIONS, USES AND THREATS , . Lake, countries, surface area, max Major ecosystem depth and volume services Major human uses Main threats Great Lakes (5 lakes) I Wetlands maintain lake I Transport I Habitat destruction USA/Canada. biodiversity (including I Water supply (2/3 of wetlands lost) 244,000 km2, 406m, migratory species) I Fishing I Eutrophication 23,000 km3 and help to remove I Recreation and tourism I Toxic and persistent contaminants I Waste disposal chemical pollution I Maintenance of I Introduced species groundwater levels I Overfishing I Local climate regulation Lake Baikal Russia (with Mongolia in I 20 percent of entire I Tourism I Untreated waste its drainage basin). world reserve of freshwater I Fishing (particularly from two 31,500km2, 1,620m, I High biological diversity I Transport (summer months) pulp and paper 23,000km3 (2,600 plants and animals, I Waste disposal plants) 1,500 endemic) I Water supply I Toxic substances of global origin (POPs) concentrating in sediments and the food chain Lake Ohrid I High biological diversity I Tourism I Dissolved phosphorus Albania/Macedonia. (60 percent of fish species I Fishing from sewage and 349 km2, 289 m, 58.7 km3 endemic) I Water supply and sewage agriculture (loading is disposal estimated to be 150 tons per year) Lake Chad I Natural barrier against I Water supply for agriculture I Excessive water Niger, Nigeria, Cameroon, desertification and human population abstraction the Central African Republic, I Habitat for endemic and I Fishing from tributaries and Chad. migratory species (including I Climate change Dry season about 2,000km2, migratory bird species 12m, 24 km3 in wetlands) Lake Victoria I High biological diversity I Fisheries (Nile perch I Eutrophication Kenya, Tanzania and (many endemic fish species) and tilapia) I Water hyacinth Uganda. I Fringing wetlands I Transportation I Introduced species 69,000 km2, 84m, 2,760 km3 I Floodplain vegetation I Hydropower (Nile perch) I Water supply I Industrial and I Sewage disposal domestic pollution Lake Tanganyika I High biological diversity I Fisheries (sardines) I Overfishing in the Burundi, Democratic (1,500 plants and animals, I Transport littoral zone Republic of Congo, Tanzania, 500 endemic) I Water supply I Excessive extraction Zambia. I Fringing wetlands I Sewage disposal of ornamental fish 33,000km2, 1,500m, I Floodplain vegetation I Pollution from urban, 19,000km3 industrial, and mining sources I Eutrophication I Increased sedimentation 10 LAKE MANAGEMENT of freshwater is annually withdrawn from the The gradual drying of these lakes should be included world's lakes, rivers, and aquifers. This is twice the in any development planning that requires addi- volume extracted 50 years ago. With such high de- tional abstractions of water. mand, it is not surprising that the service functions and ecology of lakes are sometimes severely com- Water usually enters lakes from surface runoff, di- promised. rect precipitation, and sometimes from shallow aquifers (see Note G.1). Water is lost from lakes via The lifetimes of lakes are also being reduced by overflow to rivers or streams, evaporation, seepage infilling with riverborne sediment, dense vegeta- to surrounding aquifers, and abstractions for drink- tion, or windblown desert sands. Human activity is ing water, industrial use, or irrigation. Some of these greatly accelerating these natural processes--often sources and sinks of water are quite difficult to shortening the life of lakes to as little as one-hun- measure in practice, and can usually only be esti- dredth of their natural span--through: mated when planning any abstractions of water I sedimentation of eroded soils, often caused by from a lake system. Thus, storm events in rivers deforestation and increased tillage in the lake's and streams are often missed in monitoring, and drainage basin interactions with aquifers can only be estimated. I eutrophication(excessivenutrientenrichment) I excessive abstraction of water from the lake or The shape of a lake determines many of its proper- its tributaries ties. The surface area determines how much sun- I climate change (altering rainfall patterns or in- light the lake can trap, and its shoreline length creasing desertification). determines the amount of productive littoral veg- etation. The depth (together with the local climate) This process will culminate in a wetland (see Note determines the characteristics of the water column, G.3) such as a bog marsh (a shallow lake filled with particularly its propensity to stratify (below). Con- detritus), fen, or swamp. sequently, contoured bathymetric maps of lakes are valuable aids in lake management. Lakes exist at virtually every latitude. Their evolu- tion is highly dependent upon the local climate and The flushing time of a lake is the time that it would the seasonal variations of temperature. All lakes ex- take to refill the lake from its surface and subsur- change latent heat with the atmosphere and affect face inflows if it were emptied. This may vary from the surrounding air temperature. Arctic lakes may weeks to hundreds of years. The concept is use- form above the permafrost in the summer period ful to help understand the lake's vulnerability to and refreeze during the winter. At the other extreme, pollution, but has practical limitations. For ex- shallow lakes in arid zones may become desiccated ample, in a deep stratified lake, the surface water in the summer or even for a period of several years. may flush through the lake faster than the deep For example, Lake Chad can fluctuate between water. Also, the loss of water by evaporation will 25,000 km2 and 2,000 km2 because of natural leave many of the dissolved salts behind, and they decadal-length climate cycles. will reside in the lake for much longer than its water. Climate change is having a major impact on the morphology of lakes and their evolution. The re- Detention time is a useful engineering concept for cession of glaciers is leading to the formation of the design of large reservoirs; for example, the many new lakes, particularly in the temperate en- Aswan High Dam can store 1.5 average years of flow vironment. Long-term climate modeling suggests of the Nile River. If the detention time of a dam is that many arid areas will become even drier as a insufficient, disastrous downstream flooding may result of global warming. This may well result in occur, as exemplified by the 2001 floods in the increased desiccation of lakes in these regions. Mozambique and Zambia when the gates of the 11 WATER RESOURCES AND ENVIRONMENT · TECHNICAL NOTE G.2 Kariba Dam had to be opened because of fears that Much of our understanding of lakes comes from the dam could burst with the high runoff from cy- temperate systems. Tropical lakes are not driven clone Dera. Crops were destroyed in the flooding by the strong seasonal temperature changes of their and thousands faced starvation. temperate counterparts. However, it is a popular misconception that there are no seasons in the trop- Sediment settling rates are also important for man- ics; many tropical regions experience strongly dif- agement purposes. If settling rates are rapid and ferentiated wet and dry seasons. Lake Victoria, for threaten the longevity of a reservoir, then small example, straddles the equator but stratifies dur- primary settling ponds can be built at the point of ing the rainy season when cool, dense water enters river inflow in order to trap incoming sediments the lake and sinks to the bottom, forming a ther- before they flow into the main reservoir. The ponds mocline at a depth of about 30 meters. The strong need to be dredged periodically to remove the daytime solar energy reaching tropical lakes results settled material. in temperature differences in the surface waters between day and night. THE LAKE ENVIRONMENT Solar radiation is essential for the growth of vas- Whether a lake is mixed or stratified is critically cular plants and phytoplankton, the tiny free-float- important to its functioning and management. Strati- ing photosynthetic algae that constitute the base of fied lakes are essentially two water bodies, one atop the open water (pelagic) food chain of aquatic en- the other. The bottom layer is denser than the top vironments. The euphotic zone is the layer of wa- layer, usually because it is significantly colder, al- ter that receives sufficient solar radiation for though it can also be because of different salinities. phytoplankton communities to develop. Lake wa- The point of separation is called the thermocline ters may become turbid as a consequence of dense or, for salinity stratification, the halocline. Each layer phytoplankton growth or the presence of large has separate physical, chemical, and ecological amounts of suspended sediments. Turbidity, from properties. whatever source, reduces the depth of the euphotic zone, and hence the productivity of the lake. Sunlight and wind stress are the two primary forces providing energy in a lake. Heating from Exhaustion of nutrients, particularly phosphorus sunlight becomes absorbed within a few meters, and nitrogen, will limit the production of plants warming the surface and subsurface water. Warm and algae (termed primary production) in a lake. water is more buoyant than the unheated lake Abundant nutrients will result in excess plant water, so sunlight promotes stratification of lake growth, or eutrophication. In lakes where nitro- waters. On the other hand, wind tends to mix the gen is in short supply but phosphorus is available, waters of a lake. The wind stress acts at the lake blue-green algae may become dominant because surface, and the mixing energy it produces de- many of these species are capable of obtaining creases sharply with depth. Shallow lakes are nitrogen directly from the atmosphere. This is gen- usually well mixed by the wind, and so are not erally a highly undesirable situation, because some stratified for long periods. In deeper lakes, the common species of blue-green algae are extremely mixing energy of the wind is insufficient to mix toxic to humans and animals (see Note G.4). the heated and unheated water, so stratification occurs. In temperate climates, deeper stratified The presence or absence of stratification strongly lakes may mix in the Fall, when surface waters affects a lake's chemistry and ecology. Decompo- cool and there is enough wind energy to overcome sition of organic material in the lake sediments the small temperature differential. uses oxygen dissolved in the water column. If the lake is stratified for extended periods, this decom- 12 LAKE MANAGEMENT position may remove oxygen from the bottom can support a variety of animals, including many water--a condition known as anoxia. Oxygen-de- species of fish. Benthic communities cannot pendent biota, such as fish, are unable to survive survive under anoxic conditions. in this anoxic zone. Nutrients are also released I The littoral food web marks the boundary be- from the sediments in anoxic conditions. Eventu- tween the aquatic and terrestrial environment. ally sulphate-reducing bacteria may develop, re- It includes both pelagic and benthic communi- leasing toxic hydrogen sulphide gas into the bottom ties, but is marked by the presence of plants waters. Environmental managers are very con- (emergent plants such as reeds, or submerged cerned when anoxia occurs because, when the plants such as eelgrass) and algae that grow in bottom and top waters eventually mix, the low this sunlit zone. The littoral foodweb is the most oxygen and toxic hydrogen sulphide gas spread diverse and productive system in a lake. Unfor- throughout the lake and may lead to the wide- tunately, it is the one most often damaged by spread death of fish--a "fish kill." Fish kills have human activity. often ruined attempts to develop aquaculture in poorly managed reservoirs. The value of a lake to humans and biota is gov- erned by the interaction of these diverse physical, Lakes have three inter-linked types of food web: the chemical, and biological processes (Box 1). When pelagic, benthic, and littoral webs. natural changes--such as reductions in rainfall-- I Pelagic food webs are based on phytoplankton or human interventions--such as increases in nu- and include the animals (zooplankton, fish, in- trient inputs--modify any of these processes, a com- sects) within the water column that feed on plex set of events is set in train that can result in phytoplankton. extensive, and often detrimental, changes to the I The benthic food web is based upon sediments lake. rich in organic matter termed detritus. Detritus BOX 1. FACTORS DETERMINING THE STATE OF A LAKE The natural state of a lake is determined by: I Its morphology I Physical mixing of its water, driven by wind stress (occasional or continuous mixing depending on depth) and tempera- ture (annual turnover in most temperate and some tropical lakes) I Replacement of the water by runoff and seepage into the lake and drainage out of it I Its temperature and light conditions (plankton and vascular plants grow very slowly in temperate winters, rapidly in the tropics) I The transparency of its waters I The plant nutrient balance in the lake, determined by external sources (runoff, rainwater); internal sources (recycling from the lake bottom); and sinks (food chain loss, plant or animal death and sinking to the bottom, lake drainage) I The productivity of plankton and vascular plants (depending on all of the above factors) I The oxygen balance of its deep waters (determined by mixing, flushing, and plant production and decay) I The trophic structure of plants and animals (largely dependent on all of the above factors, the geographical setting, and life history of the lake). 13 WATER RESOURCES ANDENVIRONMENT · TECHNICAL NOTE G.2 HUMAN DISTURBANCE OF LAKES POINT AND NONPOINT-SOURCE riculture and domestic use, such as pesticides, DISCHARGES OF CHEMICAL AND polychlorinated biphenyls, surfactants (deter- gents), and solvents. MICROBIAL POLLUTANTS I Chlorinated pesticides and PCBs readily bioaccumulate and may remain in the sediments The development of catchments has often included for decades. Modern pesticide formulations are the use of rivers and lakes as receptacles of pollut- more easily degraded, but are highly toxic to ants from industry, agriculture, and domestic aquatic organisms. sources (Box 2). Lakes, with their long flushing I Nitrogenandphosphoruscompoundsthatcon- times, are particularly susceptible to pollution. tribute to eutrophication (see Note D.3 for more Major classes of pollutants are: information on diffuse nutrient pollution). I Heavy metals--from industry, mining waste, I Oil and oil combustion products--from spills, domestic sewage, and some agricultural efflu- industry, domestic sources (including storm- ents (for example, copper from fungicides). water discharge), and from small craft on the Heavy metals have direct toxic effects on lake lake. biota and may accumulate in lake sediments and I Pathogens from untreated sewage are a major the lake's biota. problem in many countries. I Synthetic organic compounds--these include a I Effluents with a high oxygen demand. Most in- vast number of compounds from industry, ag- dustrial and domestic waste has a high oxygen BOX 2. THREE LAKES ENDANGERED BY POLLUTION Lake Mariut, Egypt This is a 20 km2 lake immediately to the south of the city of Alexandria, the major Egyptian seaside resort with a popula- tion of 3.5 million. From 1950 to 1985, the value of its fisheries declined from $8 million to $0.5 million annually, largely as a result of the decision to divert the city's sewage outfall from the sea into the lake. This diversion was to reduce pollution on Alexandria's beaches. Despite the treatment of some of the effluent, industry has continued to expand and discharge waste to the lake. At least 1 km2 of the lake is completely anoxic, and the polluted water flows from the lake to the sea, defeating the original objective of the diversion. Without control of the pollution at its source, the situation will remain unmanageable. Kyiv Reservoir, Ukraine This reservoir, adjacent to the city of Kyiv (Kiev), supplies several million people with drinking water. The lake lies 50 km downstream of the Chernobyl nuclear reactor, part of which was destroyed in the catastrophic explosion of 1986. To date, there has been no evidence of contamination of Kyiv's drinking water with radionuclides. However, sediments in the reservoir contain significant loads of radioactive cesium, and flooding in the Chernobyl area could transport additional loads of contaminated sediments to the lake. Continued monitoring of the situation will be necessary for several decades. Lake Baikal, Russia Lake Baikal, the world's largest lake, is a fragile environment that remains almost unpolluted except for two paper and pulp mills, which are important sources of employment in the region. The mills are responsible for 76 percent of the polluted wastewater discharged to the lake. This has damaged a 20 km2 tract of lake floor. Recent studies have suggested that high dioxin levels are associated with the larger mill. It is essential to control effluent from the pulp mills to protect the lake. The Baikal Commission was created in 1993 to coordinate the management of the basin, and the World Bank is one of the international donors assisting with the development of the lake in a sustainable manner. Sources: Hiley, P.D. 1996. In Richardson (Ed), Risk Reduction: Chemicals and Energy into the 21st Century. London: Taylor and Francis. GEF 1996. Russian Federation Biodiversity Conservation Project. Washington: World Bank. 14 LAKE MANAGEMENT demand, even after partial treatment; subsequent The critical step in applying these models is the discharge to a lake may result in oxygen deple- collection and quality assessment of available data tion in the bottom waters (see Note D.2). for calibration. Long-term, reliable data time series are needed if the model predictions are to be be- Hydrodynamic and water quality models can be lievable. used to predict the impacts of these various con- taminants as well as the likely success of different RAPID SEDIMENTATION management interventions. However, model pre- dictions are always uncertain, and managers should Deforestation and the development of extensive be aware of the limitations of the particular models agriculture in the catchment of a lake or reservoir being used. often lead to a dramatic increase in soil erosion. Much of the displaced soil will be deposited as lake The development of such mathematical models is sediments, often smothering existing benthic com- very labor-intensive. Many models have been de- munities and decreasing the depth of the lake. Fine veloped by research institutions in the last 30 years; clay particles can remain in suspension in the lake some are commercially available. Models can range waters, reducing light input and restricting primary from simple to very complex, depending on the prob- production. lem to be managed and the data available (Figure 1). A water balance model can be relatively simple, Removal of wetlands, dredging for navigation, and since a limited number of equations are needed, the isolation of river floodplains by embankments while ecotoxicological or ecological modeling will also results in an increase in the transport of sedi- be very complex, since many processes have to be ments to a lake. Sedimentation rates can be very quantified. large. For example, about 7cm of contaminated sedi- ments are accumulating each year in the huge Iron Gates reservoir between Romania and Yugoslavia, FIGURE 1. representing a major management problem. WATER QUALITY MODELS Lake Baringo in Kenya provides a classic example Volatilization of sedimentation. The lake depth has been reduced from over 15m in 1921 to 1.9m today from both re- Loading Outflow duced inflows and sedimentation. Only one of the eight rivers that used to enter the lake now flows continuously, as a result of settlement of the sur- Ab(ad)sorption rounding catchments and associated water use. Dissolved Particulate Sediment loads have greatly increased, to 5 million m3, from both the local catchments and the Mau Decay Ranges. A wetland has now formed where the Molo River enters the lake, and it is likely that the whole lake will turn into a wetland in the next few de- Settling cades. A mass balance for a toxic substance in a well-mixed lake EUTROPHICATION with no sediment feedback of solids is depicted in the figure. The toxic substance is partitioned into dissolved and particulate fractions.Volatilization and settling act These sediments can also transport nutrients into selectively on these components. the lake, causing eutrophication. Phosphorus, in particular, is readily bound to sediment material. Source: Chapra, S. C. 1997. Surface Water Quality Modeling. Nutrients can also enter the lake dissolved in the New York: McGraw-Hill International Editions 15 WATER RESOURCES ANDENVIRONMENT · TECHNICAL NOTE G.2 FIGURE 2. ACIDIFICATION TRENDS IN PHOSPHORUS CONCENTRATIONS IN THREE LAKES IN NORTHERN IRELAND, 1850­2000. The waters of mountain and high-latitude lakes have 250 very limited capacities to degrade acidic substances deposited from the atmosphere. Acid deposition from the burning of fossil fuels (particularly coal- and oil- ) 200 -1 glµ( fired power stations) has caused severe damage to many lakes in Canada, the United States, Scotland, TP 150 Norway, and Sweden, and may be affecting alpine ed lakes in Central Asia. It often results in the failure err 100 of fish larval development or deformities in adults. It has been estimated that at least 20,000 lakes are om-inft 50 affected in this manner in Sweden; as much as $27 Lough Corbet Dia Ballywillin L. million is spent annually in adding lime to these Lough Heron 0 systems to offset the effects of acid rain. 1850 1900 1950 2000 Date EXCESSIVE WITHDRAWAL OF WATER Source: redrawn from Anderson, N. J. 1997. Historical changes in epilimnetic phosphorus concentrations in six rural lakes in Northern Ireland. Freshwater Biology 38(2): 427­440 With the increased need for food production, there are increasing abstractions from lakes and the riv- ers feeding lakes, with consequent lowering of lake water as well as in organic forms. The nutrients levels. Lakes downstream of hydropower plants also can originate from natural decomposition of organic experience increasing fluctuations in their levels. matter in the catchments, from animal and human The first communities to suffer from these changes wastes, from anthropogenic sources such as fertil- are the ecologically rich ones in the lake's littoral izers, and from natural nutrient concentrations zone. originating from parent rock material. An extreme case is that of the Aral Sea. Previously For example, there are over 600 small lakes in North- 67,900 km2 in area, it has been significantly reduced ern Ireland. Research on the sediments in six of in size due to the abstraction of water from its these lakes has reconstructed a remarkable record inflowing rivers, principally the Amu Darya and Syr of changes in total phosphorus concentration over Darya Rivers, for the purpose of upland irrigation. the past 150 years that appears to be typical of lakes An extensive investigation has led to the conclusion in most developed countries. Figure 2 presents data that the original extent of the lake cannot be restored. for three lakes that have no point sources--such as Through the Aral Sea Basin Program, the World Bank sewage--draining into them. They receive inputs and other donors are focusing on rehabilitating the from surrounding agriculture. Each of the lakes irrigation infrastructure, conserving water, and pro- shows an increase in phosphorus, initially as a re- tecting the deltaic wetlands of its rivers, which are sult of land clearances (plowing increases soil loss important centers of biological diversity and pro- and attached natural phosphorus). Since the 1950s, vide sustenance for local populations. there has been a more pronounced increase in phos- phorus concentrations in two of the lakes. This re- DESTRUCTION OF NATURAL SHORELINES cent large change--due to land drainage, fertilizer AND BEDS OF AQUATIC PLANTS use, and the indirect impact of rural sanitation--is accelerating the demise of the lakes. Recent de- creases during the 1990s may reflect more prudent Many efforts to protect lakes focus on the waterbody use of fertilizers. itself and ignore the littoral zone. It is quite com- 16 LAKE MANAGEMENT mon to observe lakes in which development has FIGURE 3. replaced the natural fringing wetland transition IMPACT OF NILE PERCH ON HAPLOCHROMINES zone. Such lakes often remain aesthetically attrac- IN AKE L VICTORIA tive, but the loss of the biologically important lit- 10 toral zone severely damages their ecological Haplochromines functions. These littoral areas provide important 8 habitat for birds and aquatic fauna, intercept inflowing sediments and contaminants, and stabi- 6 lize the banks of the lake. tonnes) 4 INTRODUCTION OF EXOTIC SPECIES (1000 2 Human activity has resulted in the accidental or tion intentional introduction of a large number of plant 0 oduc and animal species to lakes across the world. Spe- 100 pr Nile perch cies may be introduced by accident--for example, fish through attachment to ships and boats or by escapes 80 cial from aquaria, fish farms, or as bait for anglers. In- tentional introductions have been for "improve- 60 ment" of fish stocks, ornamental purposes, or control ommerC of undesirable plants or animals (Box 3). Introduc- 40 tions are almost always detrimental to the natural ecology of a lake, although they may confer major 20 economic advantages. 0 In a well-known example, some Nile perch were 1970 1972 1974 1976 1978 1980 1982 1984 1986 1988 1990 introduced to Lake Victoria in the late 1950s. This Year voracious predator gradually adapted and began to Source: Ogutu-Ohwayo, R. 2001. "Changes in life history be caught in appreciable numbers by the early 1970s. characteristics of Nile perch, Lates niloticus, in Lake Victoria and By 1980 it had caused a rapid decline in native the implication on the future of its fishery in the lake." LVEMP cichlid stocks (Figure 3), and has been a major fac- Conference, Kisumu, Kenya. BOX 3. SOME DAMAGING INTRODUCTIONS Water hyacinth (Eichhornia crassipes), a native of South America, is now found in most tropical countries. It can spread over tens of km2 within a year of introduction. It prevents light from penetrating the lake surface and depletes oxygen in the water, resulting in anoxia and the elimination of many species. It can also greatly increase transpiration losses of water from the lake surface. Examples of lakes with serious hyacinth problems are Lake Victoria, Africa; Lake Chapala, Mexico; and Chilika Lake in Orissa, India. Zebra mussels were accidentally introduced from Central Europe to the Great Lakes in the late 1980s. They have now spread through many internal waterways in the United States. They attain large populations, displacing local bivalves and clogging cooling pipes. Attempts at control have been unsuccessful so far. Sea lampreys, a parasitic fish native to the North Atlantic, invaded the upper Great Lakes after the construction of the Welland Canal in 1929. This parasite, together with overfishing, led to the collapse of the lake trout fishery by the late 1950s. Currently, the sea lamprey is partly controlled by a selective toxicant applied to streams to prevent spawning. Ruddy ducks, a native of North America, were introduced to Western European lakes for ornamental purposes but now threaten endangered native species by crossbreeding. Plans are being made to eliminate the species through hunting. 17 WATER RESOURCES AND ENVIRONMENT · TECHNICAL NOTE G.2 tor in the extinction of 200 to 400 species of the lake's FIGURE 4. endemic fish. ANNUAL FISH CATCH FROM KENYAN PART OF AKEL VICTORIA 140 However, the Nile perch, together with the Nile tila- L niloticus (Nile perch) pia, became the basis of a new and sophisticated R.argentea 120 Haplochromines trawl fishery. This fishery is now a significant con- tributor to the export earnings of all three riparian 100 countries. Kenya earned $34 million in 2000 from tons) 80 exports of Nile perch. While this new industry was beneficial to the national economies, it was detri- (,000 60 mental to local communities that had been previ- ously dependent on catches of native fish. tchesaC 40 Consequently, these groups have decreased access 20 to a cheap source of protein. Thus, the effects of this introduction were not simple: some groups in soci- 0 ety benefited financially and others have suffered, 1976 1978 1980 1982 1984 1986 1988 1990 1992 1994 1996 1998 2000 while there has been a major decrease in biodiversity. Year Source: Njiru, M., A. Othina A. & E. Wakwabi. OVEREXPLOITATION OF FISHERIES 2001. "Impact of water hyacinth on the fishery of Lake Victoria, Kenya." LVEMP Conference, Kisumu, Kenya. Overfishing is a major problem in some lakes, not only because of its economic consequences, but also because of the ecological implications. Thus, there is now good evidence that Nile perch in Lake Victoria Removal of the top fish predators through overfish- are being overfished, with significant decreases in ing may result in effects throughout the foodchain. landings in recent years(Figure 4). One of the ma- For example, grazing pressure may be reduced on jor causes has been the reduction in net mesh size, free floating or attached algae, thus promoting al- resulting in the capture of many juvenile fish be- gal blooms (See Note G.4). However, the ecological low reproductive age. The problem is being tackled interactions in lakes are so complex that it is very by encouraging fishing communities to take more difficult to predict whether overfishing will result responsibility for the regulation of their industry. in the promotion of nuisance species or not. POLICY APPROACHES FOR IMPROVING LAKE MANAGEMENT Many of the current threats to lakes and reservoirs-- pation, and the linkage of economic causes and ef- such as sedimentation and eutrophication--originate fects (transfer of benefits and responsibilities) by well beyond the margins of the lakes themselves; applying economic instruments. corrective or preventive actions are often necessary across the entire watershed. This section will dis- INTEGRATED CATCHMENT cuss a policy approach that requires integrated MANAGEMENT IN THE CONTEXT catchment management, as well as some of the con- OF LAKES straints to implementing this approach. This ap- proach is designed to incorporate the management of lakes and reservoirs into the process of sustain- Integrated Water Resources Management (IWRM) able development. The approach includes sectoral is embedded in the Bank's 1993 Water Resources cooperation and joint planning, stakeholder partici- Management Policy and is the framework adopted 18 LAKE MANAGEMENT in the World Bank's new Water Resources Sector Strategy. One of the underlying reasons for the deterioration of many lakes is the poor understanding among managers and the general public of the boundaries of the hydrological system, in both spatial and tem- Bank poral terms. Activities that may provide short-term orld W, benefits in the upper catchment of a river often lead to longer-term detrimental consequences down- Carnemark stream, including in lakes. Unfortunately, the Curt strongly sectoral organization of governments does by not usually lead to policies that integrate all of the Photo costs and benefits of a proposed action into a com- Guatemala mon decisionmaking process. Integrated catchment management (ICM) promotes onstrated that natural wetlands and floodplains are the management of water resources on a whole- the most effective means of controlling floods and catchment basis rather than by conventional admin- reducing sediment transport. istrative boundaries. The costs and benefits of development need to be assessed across the full A particularly difficult problem exists with projects catchment. This may require re-aggregation of ex- that include new dams or reservoirs. Where a res- isting economic data to fit the catchment bound- ervoir is likely to suffer gradual siltation, it is nec- aries. In this manner, true project costs for a variety essary to assess the cost of remedial action or of alternatives can be compared with the potential decommissioning across its projected lifetime. There benefits. For example, the discharge of nutrients is little experience on how to do this because con- from agriculture may have little impact within a par- ventional economic techniques heavily discount ticular tributary, and so there will be little local in- even large costs in future years. The World Com- centive to control it. But it may have major mission on Dams has conducted an integrated eco- downstream consequences for a lake. Thus, upland nomic analysis of a number of case studies across farmers are unknowingly subsidizing their produc- the world, but cautions that "applying a `balance- tion through consumption of environmental capi- sheet' approach to assess the costs and benefits of tal downstream. The policy framework, including large dams, where large inequities exist in the dis- regulatory or market mechanisms, for the overall tribution of these costs and benefits, is seen as un- catchment must be strong enough to internalize acceptable given existing commitments to human such externalities or pay the cost of remedial ac- rights and sustainable development." tion. In practice, this is quite difficult to achieve. The development and implementation of environ- Poor catchment land-use practices have contributed mental policies for the use, protection, and restora- to many of the problems affecting lakes and reser- tion of lakes requires a strong information base. This voirs (Box 4). The increasing sediment loads in in turn requires a long-term commitment to re- many rivers during flood times arises from a com- search, monitoring, and evaluation (see Note D.1). bination of erosion and the removal of sediment Environmental monitoring of two types is usually deposition zones, such as floodplains, through de- required: (1) compliance monitoring, to ensure that velopment. Sediments and attached contaminants regulations are enforced and milestones met; and are best controlled at the source--after all, erosion (2) status and trends monitoring, to evaluate changes represents a loss to farmers as well as a cost to down- in environmental health and to help set new objec- stream water users. Numerous studies have dem- tives and policies. 19 WATER RESOURCES AND ENVIRONMENT · TECHNICAL NOTE G.2 BOX 4. LAKE PATZCUARO, MÉXICO Lake Patzcuaro is 130 km2 in area and has a mean San Jeronimo depth of 5 to 8 meters. The catchment has no rivers, Purancheouaro only small streams that feed the lake during rainy v Santa Fe de la Laguna San Andres Quiroga periods. With its eight islands and mountainous Tzinrondaro v landscape, it is a place of outstanding natural o beauty and remarkable biological diversity. The basin v de PatzcuarIchupo includes 120 villages and two major towns, which are Lago Tzintzuntan Ucasanastacua experiencing accelerated growth. The region has a v Isla Pacanoa Puacuaro large indigenous population, many of whom inhabit Isla Yumuan Eronguaricuaro the islands in the lake, which has traditionally relied San Pedro Cucuchuchu San Francisco on subsistence farming and fishing. The lake is a Uricho Isla Janitzio Ihuatzio national and international tourist attraction and there Jaracuaro has been a recent shift to service industries. Forest Settlement The major problem affecting this lake is the dramatic PATZCUARO v Volcano deforestation of the catchment and conversion of v land to cattle ranching with increased settlement Lake density. This has resulted in massive soil erosion (64- Lake Patzcuaro showing settlements and forested areas 140 million m3 of sediment annually deposited in the lake) and reduced inflows. As a result, water levels in the lake are receding, rapidly threatening the major asset of the region and its biological diversity. Furthermore, the lack of sewage treatment and the use of fertilizers has led to the eutrophication of the lake. Over 28,000 m3 of untreated waste are now discharged to the lake every day. More than 20 Mexican federal institutions are engaged in development and environmental protection in the area. However, this has not resulted in measurable improvements in the lake or in the social welfare of local people. There is no long-term management strategy, and little or no integration of effort across the various agencies. The situation is exacerbated by frequent changes in local officials and disregard of the traditional knowledge of indigenous people. More recently, the federal and state governments have agreed on priority programs for reforestation and protection of forests, regulation of fisheries, erosion control, and the control of siltation. A major program is also being developed in environmental education and strengthening of civil society. It remains to be seen whether these actions will result in the integrated approach necessary for managing the catchment and protecting the lake. INSTRUMENTS FOR IMPROVING designed to provide information to help LAKE MANAGEMENT decisionmakers properly weigh the benefits of a project against its impacts on stakeholders and on the integrity of the environment. For lakes and res- Note B.2 provides a general introduction to instru- ervoirs, it is necessary to examine impacts in the ments available for water resources management. entire watershed and, if there are migratory species, This section will describe the use of specific instru- beyond it. Environmental assessments, incorporat- ments in the context of lake--and associated catch- ing the views of persons affected by the project--in- ment--management. cluding indigenous people, the poor, and Regulatory instruments. These typically include laws disadvantaged groups--are also a requirement of the (statutory and customary) and regulations as well World Bank for the projects that will have environ- as the administrative procedures for enforcing them, mental impacts. However, there is room to improve such as prohibitions, permits, or licenses. many of these assessments with early and better stakeholder participation and an evaluation of a wider Most countries require environmental impact assess- range of alternatives. ments (EIAs) for proposed developments. EIAs are 20 LAKE MANAGEMENT Economic Instruments. Note B.2 provides details of I Fishing Licenses. It is common in the devel- several economic instruments--such as tariffs, user oped world for goverments to partly finance the fees, and pollution penalties--that may be applied management of lakes through fishing licenses. to the management of lakes and reservoirs. How- These recognize the cost of managing the fish- ever, it is particularly difficult to find viable mecha- ing resource. A fishing levy has been proposed nisms to cover long-run costs such as reservoir for Lake Victoria in East Africa as a means of decommissioning or eventual lake rehabilitation. having the fishing community recognize the cost Some instruments useful for lake management are: of exploiting this natural resource. I Pollution charges. This involves paying a fee that reflects the environmental damage for ev- Participatory Instruments. The involvement of stake- ery unit of wastewater discharged. This encour- holders is a fundamental part of ICM. This inevita- ages factory managers to adopt measures for bly requires community-level participation. water conservation, recycling, and treatment Stakeholders in the case of lake or reservoir man- prior to discharge. agement may include users of the lake itself such I Tradable discharge permits. If a total accept- as local authorities, fisherfolk, recreational users, able level of discharge to a lake can be estab- power generation company staff, water distribution lished (particularly for nutrients and biodegrad- and sewage authorities, as well as catchment groups able organic material), permits can be issued such as farmers, urban community groups, and in- up to this level. These permits can then be traded dustrialists. Other interested parties include scien- on a market. This approach will only work if tists, conservationists, and the public in general. the number of sources within the lake catch- Local or international NGOs are often important ment area is large enough to sustain a reason- actors in lake conservation programs. Involving able level of trading without any one source these stakeholders promotes choice and enables having a disproportionate influence on the mar- transparency and accountability (Box 5). It reduces ket. A similar approach may be employed for conflicts and fosters commitment to the manage- trading permits to fish or extract any other re- ment options selected, although there are consid- newable resource from the system. erable costs arising from the time and effort needed I Subsidiestoenvironmentallysoundmanage- to engage these groups. ment practices. Subsidies are inefficient instru- ments but may be justified for practices such Environmental education is essential in order to as integrated pest management and organic ensure long-term sustainability of a participatory farming if they reduce the cost of environmen- process. It should be conducted at two levels: tal damage that society would otherwise have (1) public awareness of the problems of environ- to bear. mental degradation, especially the linkages between BOX 5. INTEGRATED CATCHMENT MANAGEMENT AND THE GREAT LAKES The Great Lakes, shared between the United States and Canada, measure more than 15,800 km2 in area. They ac- count for 20 percent of the world's surface freshwater supply, and 95 percent of the surface water in the United States. Joint management of the lakes began in 1909 with the establishment of the International Joint Commission. The lakes have suffered serious environmental decline due to chemical pollution, introduced species (Box 3), and overfishing. Conventional approaches to pollution control proved inadequate, and in the 1970s scientists and resource managers called for an integrated ecosystem-based approach, including the participation of the main stakeholder groups interested in the lakes. Following a comprehensive assessment, 42 areas of concern were identified for urgent action using the integrated approach. For each of these areas, a remedial action plan (RAP) was created. The RAPs helped to set priorities and coordinate remedial activities, but they have not fundamentally changed the predominant sectoral nature of resource management in the catchment. Source: Mackenzie, S.H. 1987. Environmental Management. 21(2): 173-183. 21 WATER RESOURCES AND ENVIRONMENT · TECHNICAL NOTE G.2 catchment activities and consequences on down- gal prerogatives; the responsibilities of the actors stream waterbodies such as lakes and reservoirs, involved; actions to be taken, with milestones and and (2) formal education of young people, in order economic costs; provisions for monitoring and evalu- for them to understand the central role of the natu- ation; and the institutional arrangements for coor- ral environment in their future welfare. dination. Without a clearly identifiable local coordinating and implementing mechanism, the plan is almost certain to fail. Box 6 provides a good INSTITUTIONAL ARRANGEMENTS FOR example of a coordinating mechanism that takes the NATIONAL AND TRANSBOUNDARY LAKES form of a permanent lake commission. This mecha- nism is proving relatively successful, but has still At the national level, the major challenge for lake failed to curb illegal use of the lake for shrimp farm- management is to achieve the political support nec- ing. essary to achieve a coordinated policy approach among the various sectors whose activities affect At the international level, nearly half of the world's lakes. The agreed approach can be enshrined in a largest lakes are shared among two or more coun- Lake Management Plan following the principle of tries. Although this does not change any of the prin- ICM. The plan should clearly define objectives; le- ciples involved, it adds considerably to the BOX 6. DEVELOPMENT OF A COORDINATION MECHANISM : CHILIKA LAKE, ORISSA, INDIA Chilika is India's largest lake. It is a coastal lake connected to the Bay of Bengal and supports a number of economic activities, including fishing (100,000 fisherfolk) and tourism. The brackish lake is suffering from a number of serious problems, including siltation, shrinkage of area, choking of the inlet as well as the outer channel to the sea, decrease in salinity, weed infestation, decrease in fish productivity, and an overall loss of biodiversity. There is a serious ongoing social conflict between traditional fisherfolk and operators of illegal shrimp aquaculture units. In response to the declining environmental situation, the Government of Orissa created the Chilika Development Authority (CDA) in 1992. It is part of India's National Lakes Management Programme and has the following principal objectives: I To protect the lake ecosystem and biodiversity I To execute multidisciplinary developmental activities, either by itself or through other agencies I To collaborate with other institutions--state, national, or international--for integrated development of the lake I To establish a management information system and database of the lake I To promote long-term multidisciplinary research, prepare environmental status reports, and establish a research cen- ter for the lake. CDA has partnered with a number of local, state, national, and international institutions and nongovernmental organiza- tions to carry out scientific investigations. These include understanding the biophysical and ecological nature of the complex lagoon and how it functions; determining the threats faced by the lake; monitoring the in-lake hydrology and ecology, and the catchment water quantity and quality; modeling the biophysical processes of the lake; and predicting the changes in sediment dynamics in response to changes in flow within the lake and between the lake and the sea. As a result of these studies together with monitoring information and modeling, CDA has carried out a major restoration effort to improve the lake's hydraulics. In September 2000, with the support of the Government of India, they dredged large sections of sediment deposition within the lake and cut a new opening to the sea. The restoration efforts have resulted in impressive changes in water quality (salinity levels are much higher), in freshwater flow patterns, and increases in zooplankton densities. The endangered Irrawady Dolphin (Orcaella brevirostris) has returned to Chilika Lake; many species thought to have been locally extinct are now found; and fish, crab, and shrimp production has dramatically increased. The income of the fisherfolk has more than doubled in the last 3 years. This work has been recognized by the Ramsar Secretariat, which recommended the removal of Chilika Lake from the Montrex List as a threatened wetland and granted CDA a Ramsar award. CDA is now working on developing a long- term plan to manage the lake sustainably. 22 LAKE MANAGEMENT complexity of management. For example, it is diffi- for transboundary lakes have existed for over 100 cult to set uniform water quality and effluent dis- years, but these have traditionally focused on ex- charge standards among riparian countries with ploitation and territorial issues rather than envi- different industrial bases and traditions. ronmental protection. However, these require a high-level of agreement and cooperation between Management of these systems requires cooperative the relevant countries and are not the only option institutional structures, empowered through appro- for lake management. In the past two decades, there priate policy, legal, and financial instruments, and has been increasing awareness of the fragility of staffed with personnel trained in lake management lake environments and the need for integrated man- and conflict resolution. International commissions agement practices across countries. BOX 7. TRANSBOUNDARY LAKES IN EAST AFRICA: MANAGEMENT APPROACHES AND THE INVOLVEMENT OF THE GEF Lake Victoria Environmental Management Project. Lake Victoria is shared by Kenya, Tanzania, and Uganda. Following an integrated approach, 14 pilot zone activities are intended to develop groundwater resources; conserve and develop wetlands; reduce sediment and nutrient flow, especially of phosphorus; reduce fecal coliform and municipal nutrient output; regulate industrial effluent; identify contaminants in fish and prevent any increase; stabilize the catch of Nile perch; increase the catch of indigenous species; increase incomes of local fisherfolk; and reduce water hyacinths to manageable levels. Lake-wide actions have assessed and measured sources of nutrients causing eutrophication; measured fisheries-trophic state interactions; modeled and monitored lake circulation; defined and measured the contaminant threat; harmonized regulation and legislation; monitored recovery and impact; and built institutional capacity. The project has been extended to 2004; a second phase, focused on implementing management actions using the knowledge base developed in the first phase, is being prepared. Lake Tanganyika Biodiversity Project. Burundi, DR Congo, Tanzania, and Zambia all border Lake Tanganyika. The acceler- ating rate of environmental change caused by overfishing and eutrophication is now much faster than the fauna's adaptive capabilities. The lake's problems start on the land. Ownership and responsibility for land maintenance is uncertain and information on better techniques has not reached the practitioners. The conflict in Burundi and DR Congo has made the implementation of this project very complex. The initial 5-year phase of the project was completed in July 2000, with the principal outputs being a body of technical studies on the biodiversity of the lake and the threats to it; a regionally agreed Strategic Action Program (SAP); and a draft legal convention. The SAP involved local communities in its development, embracing the dual needs of development and conservation. A follow-on project is now being prepared to implement the SAP. Lake Malawi/Nyasa Biodiversity Conservation Project. Lake Malawi/Nyasa, the third largest lake in Africa, is shared by Malawi, Tanzania, and Mozambique. The lake is reputed to have the highest biological diversity of fish species in the world. Over 90 percent of the fish species are endemic to this lake. The lake provides abundant water for domestic uses in a water-scarce region; supplies essential and cheap protein through its fisheries; facilitates transportation and irrigation, especially downstream in the Shire River; contributes to hydroelectric energy production; attracts tourists; and provides recreational and aesthetic opportunities. A recent massive fish kill (1999) exemplifies the danger of increasing human pressure on the system, and there is growing evidence of eutrophication, habitat destruction, and overfishing. The three biggest challenges to the project and to conserving the biodiversity of the lake while allowing sustainable utilization are 1) to increase awareness among riparian peoples of the natural wealth the lake represents; 2) to under- stand how the lake has come to express and maintain such great biodiversity; and 3) to increase the resident expertise of the three countries to implement the management plan. The GEF project in this lake was a relatively small "enabling" project with diverse activities, including reviews of environ- mental law and regulations, strategic park planning, environmental education, water quality assessment (WQA), zoogeography, fish taxonomy, and fish ecology. Under the WQA, the quantification of all the major nutrient inputs and outputs has been achieved for the first time on an African Great Lake. Perhaps the biggest challenge has been to engage local stakeholders using innovative activities such as the "Theatre for Africa," which has been highly successful. Postgraduate work for students, field training for environmental education extension officers, and on-the-job training for national research officers and technicians is ongoing. There are no plans at present to fund a follow-up GEF project. 23 WATER RESOURCES AND ENVIRONMENT · TECHNICAL NOTE G.2 The World Bank is currently implementing a num- another of the GEF implementing agencies-- is imple- ber of transboundary, GEF-funded projects. These menting similar projects for Lake Tanganyika, include Lake Victoria (3 countries), the Aral Sea (5 Lake Titicaca, and Lake Peipsi. A summary of the countries), Lake Ohrid (2 countries), Lake Malawi GEF interventions in East African lakes is provided (3 countries), and Lake Chad (5 countries). UNDP-- in Box 7. TOOLS FOR REMEDIAL ACTION Remedial actions for seriously damaged lakes and The most common water quality problems encoun- reservoirs tend to be expensive and may either pro- tered in lakes are excessive growth of either algae vide a temporary respite, involving high recurrent or nuisance aquatic weeds, although other quality costs, or transfer the problem downstream. As a issues such as accumulation of pesticides or heavy general rule, it is more cost-effective to control prob- metals, acidification, and salinization can also se- lems at their source than to undertake remedial riously affect lake biota. Algal blooms and aquatic action. Nevertheless, remedial approaches are some- weeds can be tackled using a variety of techniques. times unavoidable. For example, Lake Washington, The choice of technique will depend on the causes situated near Seattle, Washington in the United of the problem and the expertise and funding avail- States, has received discharges from industry, do- able. Techniques are briefly described below; Note mestic sources, agriculture, and logging since early G.4 provides detailed information. in the 20th Century. It was seriously eutrophied by the early 1950s. In 1958, a project began to divert ALGAL BIOMASS CONTROL effluent from 11 sewage treatment plants to dis- charge directly to the sea following primary treat- The main techniques for controlling the biomass ment. The engineering works were completed by of algae in eutrophic lakes are summarized in 1967, and by 1975 the lake had recovered to a near- Table 2. pristine state. The capital cost of this work was high, $366 million ($650 per capita) at 1990 costs, with MACROPHYTE BIOMASS CONTROL an annual operating cost of $2.1 million. The in- tensive recreational use of the lake alone provides Excessive growth of aquatic plants may severely benefits that exceed this cost. reduce the useful lifespan of the lake. In tropical systems, the presence of floating water hyacinths Water quantity problems--either periodic or perma- may result in the complete breakdown of the natu- nent reductions in lake levels--inevitably require ral lake ecosystem. action at the source of the problem. For example, water hyacinths started to spread in Lake Victoria at the end of the 1980s. By 1996, the floating mats had become so dense that ports were becoming blocked. Mechanical means were inca- Bank pable of harvesting such a large biomass. Later the orld W, same year, trials began of introductions of a wee- vil, Neochetina sp., originally from South America. Carnemark Initial results of the introduction were discourag- Curt ing, but in December 1999, local scientists reported by that 60 percent of the hyacinths had been eliminated Photo from the lake. The reasons for the sudden reduc- Indonesia 24 LAKE MANAGEMENT TABLE 2. TECHNIQUES FOR CONTROLLING ALGAE IN EUTROPHIC LAKES Technique Example Costs1 Advanced wastewater treatment. This usually involves Diversion: Lake Typical per capita costs removal of phosphorus from effluents discharging to the lake, Washington (USA), of diversion (1990 prices) since algal communities in lakes are often phosphorus- Lake Norrviken are $350 to $1,350, limited. Phosphorus can be removed with aluminium sulphate (Sweden); with annual O & M costs (alum), calcium carbonate (lime), or ferric chloride (iron). from $4 to $16. This is worthwhile only when significant proportions of nutrients AWT: Shagawa Lake Per capita costs for AWT come from point sources. Effluents can also be diverted (USA), Lake Zurich are typically $600 to $1,100, entirely away from the lake, such as to land disposal on (Switzerland) with annual O & M costs tree lots. between $77 and $115. Dilution and flushing. This depends upon the availability of a Moses Lake (USA), Highly variable large volume of clean freshwater to flush the lake at regular Lake Veluwe intervals and physically replace eutrophic water. (Netherlands) Use of this freshwater may impose costs on upstream water users. Hypolimnetic withdrawal. The removal of high nutrient, low Lake Bled (Slovenia), Typically under $1 million; oxygen, bottom waters of smaller lakes (usually less than Lake Kortowo (Poland) very low O & M. 4 km2). This is achieved by constructing a siphon tube from the lake bottom to replace the surface outflow from the lake. It may lead to further problems downstream. Phosphorus inactivation. Phosphorus bound in lake Alum application ­ $640/ha (3 Mile Pond); sediments may continue to be released for long periods of L. Langsjon (Sweden); $3,900/ha (L. Trekanten) time if the bottom waters remain anoxic. It is possible to 3 Mile Pond (USA); (1990 prices) reduce phosphorus concentrations in the water column by Riplox ­ L. Trekanten chemical precipitation or to retard phosphorus release from (Sweden) sediments. Chemicals used are aluminium salts, which form a colloid that settles on the lakebed and takes up phosphorus. An alternative involves less environmentally damaging calcium nitrate application to oxidize surface sediments (Riplox process) Biomanipulation. Management of the food web to enhance Lake Michigan (USA) ­ Typically $300 to $600/ha the grazing of algae. The technique is not always successful control of lamprey, capital cost. because of the complexity of aquatic foodwebs. It requires restocking of salmon. a comprehensive understanding of the ecosystem. Bautzen Reservoir, Germany ­ unsuccessful example of long-term restoration Algicides. Algicides, such as copper sulphate, can be Casitas Res. $30 to $700/ha sprayed on the lake surface to kill algal blooms. Although (California, USA) for a single application temporarily effective, they have major negative impacts on depending on dosage the ecosystem and should only be used for crisis situations. 1Estimates are taken from Cooke, G.D, E.B. Welch, S.A. Peterson. and P.R. Newroth. 1993. These refer to a limited number of case studies and are presented for indicative purposes only. tion are not properly understood, although the wee- The various techniques to control nuisance mac- vils undoubtedly contributed. Water hyacinths had rophytes are summarized in Table 3. Chemical ceased to be a major problem by 2001 although, methods are not discussed, as they are considered given favorable conditions, the problem could re- environmentally unacceptable occur. (See Note G.4.) 25 WATER RESOURCES AND ENVIRONMENT · TECHNICAL NOTE G.2 TABLE 3. TECHNIQUES TO CONTROL NUISANCE MACROPHYTES Technique Example Costs Water-level drawdown. This is a relatively simple technique Commonly employed Typically $5 per ha. employed in smaller reservoirs. The water level is lowered in technique in in the United States. order to expose the lakebed in the littoral zone. Exposure of temperate reservoirs roots for sufficient time during freezing or dry, hot conditions in the United States. will kill the plants. Negative consequences include possible algal blooms after reflooding and damage inflicted on wetland communities. Not always effective if the nuisance plants produce persistent seed stock. Preventative and manual methods. Prevention involves Eurasian watermilfoil Diver dredging typically regulatory and public awareness measures to avoid the removal in the $4,000 to $16,000/ha introduction of nuisance exotic species. Manual methods for United States and (Canada). Harvesting, removal include (1) diver-operated dredges; (2) harvesting of Canada (species indicative cost $400 to plant biomass (using single or multiple stage harvesters); and introduced in the $1,400/ha. Derooting (3) derooting by barge-mounted rototillers or similar equipment. 1940s); restoration of (indicative) $900 to Environmental effects are minimal (mostly because of the small Lake Hornborga, $1,200/ha. areas treated) but regrowth is almost inevitable. Sweden Capital costs of the equipment used is highly variable (typically $30,000 to $100,000 for a medium- sized harvester). Sediment covers. By physically covering sediments with an The techniques have Approximately $6,200 to impenetrable material, plants are prevented from rooting been employed in $17,000/ha or growing. Typical materials employed are polyethylene, British Colombia, polypropylene, fibreglass/PVC (Aquascreen), or burlap. The Canada to control method is symptomatic; removal of the cover soon results in Eurasian watermilfoil regrowth unless preventive measures are taken. It may also "balloon" when gases are naturally released from the sediments. Biological controls. Exotic macrophytes proliferate partly Aligatorweed, introduced $70 to $200 (for Grass because of eutrophication, but partly because of the absence to the US in 1884, choked Carp) of natural controls. By studying the plants in their native habitat, many ponds and lakes it is sometimes possible to identify the control agent and until the stem-borer, transfer it to the site of the invasion. This carries its own risks, as Agasicles, was released the control agent may attack native species in the new habitat in 1964, eliminating 98 and worsen the environmental damage. The control agent percent of the weed in should be specific to the invasive species, or easily removed 17 years; Grass carp following the successful intervention. were used to clean Lake Parkinson in New Zealand of an exotic plant. MULTIPLE BENEFIT TREATMENTS Water quality monitoring is a central element of management whose costs are not incorporated into Table 4 illustrates techniques that can have mul- the above estimates. These lake interventions, by tiple benefits, including algal control, control over themselves, may overcome an immediate problem. release of toxicants, and habitat renewal. However, However, they will almost always need to be aug- all are based on engineering approaches, which mented by longer-term measures through the ap- can be costly and require significant technical ex- plication of policies and practices for ICM. pertise. 26 LAKE MANAGEMENT TABLE 4. MULTIPLE BENEFIT TREATMENTS Technique Example Costs Hypolimnetic aeration. A characteristic of eutrophication 420 ha Tegeler See, Highly variable, Tegeler is the depletion of O in bottom waters (the hypolimnion). Germany, 12 m3 air/min. See installation cost was 2 In small lakes and reservoirs where preventive measures have from 15 airlifts; $2.7 million, $6,500/ha/ failed, aeration of the hypolimnion may alleviate the problem. Kolbotnvatn, Norway, yr operation. 5.5 m3 air/min; Artificial destratification. The objective is to promote circulation Commonly employed in Typical installation costs between bottom and top layers of a stratified lake to enlarge the small eutrophied systems are $720/ha; habitat for animals, maintain oxygenation, and reduce internal P in the United States, corresponding cycling. Mixing is promoted by injecting air into a horizontal pipe Germany, Poland, operating costs would perforated with a series of holes, lying at the bottom of a lake. Sweden, Canada, be $320/ha/yr. A curtain of bubbles will rise from the pipe to the surface, entraining Australia, and the United Financially impractical water with it. Typically very energy intensive unless designed to Kingdom for large lakes. maximize natural mixing from wind forces. Sediment removal. A technique for effectively creating a new Lake Trummen, Sweden, Lake Trummen benthic system. It removes the sediment nutrient pool, eliminates 100 ha, received effluent restoration cost about rooted macrophytes, and restores effective circulation. from 1895-1970. 1m of $5,700/ha (should be Mechanical, hydraulic, and pneumatic dredges may be employed. accumulated sediments amortized over a There are serious environmental considerations and the technique removed in 1970-71, 25-year period) is only justified in chronic cases. Species may be lost and benthic 90 percent reduction habitats destroyed. Furthermore, disposal of contaminated in dissolved total P dredged material is a major problem. achieved, lake now used for wildlife and recreation. Care should also be taken to incorporate procedures to recover after a major intervention, but may need for encouraging habitat restoration in any lake re- to be provided with artificial islands or rafts for nest- habilitation project. For example, migratory water- ing. fowl cannot wait for two or three years for habitats FUTURE CHALLENGES The 1997 UN Comprehensive Freshwater Assessment At a local or regional level, there will be more chal- of the World concluded that all economically ac- lenges such as that faced in the restoration of Lake cessible water in the world would need to be uti- Sudoche, which is part of the Amu Darya river delta lized in order to grow enough food for everyone to that used to be contiguous with the Aral Sea. Engi- receive a healthy diet and for industrial, household, neering solutions can reshape the hydrology of Lake and environmental needs to be met. There will in- Sudoche, providing that the countries in the Amu evitably be increasing competition in meeting these Darya catchment are willing to release water to main- needs. ICM offers the framework for reconciling tain its level. Restoration is now under way as part of these competing demands, but actual implementa- the World Bank/GEF Aral Sea Basin Programme, and tion will require increasing support from donors the prospects for the lake are positive. such as the World Bank, UNDP, UNEP, and the Global Environment Facility in the specific case of The kind of trade-off confronted in the case of Lake transboundary waterbodies. Sudoche is likely to become increasingly common 27 WATER RESOURCES AND ENVIRONMENT · TECHNICAL NOTE G.2 in arid regions of the world. This is why it is impor- use of engineering techniques for restoration, will tant to understand lakes, not as isolated water bod- help to maintain the vital role of these waterbodies ies, but as a functional component of the larger and that of the ecosystems and social amenities they catchment area. Strategic impact assessments and support. the application of ICM, together with the judicious FURTHER INFORMATION The following references provide general informa- Dinar, A., P. Seidl, H. Olem, V. Jorden, A. Duda, and R. tion on lake and reservoir planning and manage- Johnson. (1995). Restoring and Protecting the World's Lakes and Reservoirs. World Bank Tech- ment. nical Paper No. 289. Washington, D.C.: The World Bank. Ayres, W., A. Busia, A. Dinar, R. Hirji, S. Lintner, A. Eiseltová, M., ed. 1994. Restoration of Lake Ecosystems: McCalla, and R. Robelus. 1996. Integrated Lake A Holistic Approach. London: International Wa- and Reservoir Management. World Bank Tech- terfowl and Wetlands Research Bureau Publica- nical Paper No. 358. Washington, D.C.: The World tion 32, Slimbridge, UK. Bank. United States Environmental Protection Agency (USEPA). ILEC/UNEP. 1988-98. Guidelines in Lake Management, 1988. The Lake and Reservoir Restoration Guid- Vols.1-8. Nairobi, Kenya: UNEP. (also available ance Manual. Washington, D.C.: USEPA. at EarthPrint.com). UNEP GEMS. 1994. Environment Library No. 12: The Some useful websites with information on lake and Pollution of Lakes & Reservoirs. Nairobi, Kenya: reservoir management are: UNEP. (also available at EarthPrint.com). World Lake Vision Committee. 2003. World Lake Vision: The Global Environment Facility A Call to Action. Shiga, Japan: ILEC/UNEP/Shiga http://www.gefweb.org Prefecture. The Global International Waters Assessment (a GEF pro- ject to examine the root causes of degradation in inter- The World Commission on Dams contains a thor- national waters) ough description of reservoir planning and devel- http://www.giwa.net opment. The Bank has endorsed its core values and The World Commission on Dams strategic priorities for its own lending. http://www.dams.org International Commission on Large Dams World Commission on Dams, 2000. Dams and Develop- http://icold-cigb.net ment. London: Earthscan Publications. Lake Ohrid cooperative project http://www.allcoop-macedonia.homestead.com/ The following document provides guidance on lake locp.html monitoring: Update on the Lake Chad Basin Commission http://www.oieau.fr/ciedd/contributions/atriob/ resume/rcblt.htm UN/ECE. 1996. Current practices in monitoring and as- sessment of rivers and lakes. Vol. 2. Geneva: UN/ Lake Tanganyika Biodiversity Programme ECE Task Force on Monitoring and Assessment. http://www.ltbp.org Great Lakes Environmental Atlas and Resource Book Restoration of lakes is described in the following http://www.epa.gov/glnpo/atlas/intro.html publications: International Lake Environment Committee http://www.ilec.or.jp Cook, C.D., E.B. Welch, S.A. Peterson, and P.R. Newroth. LakeNet 1993. Restoration and Management of Lakes and http://www.worldlakes.org Reservoirs, Second Edition. Boca Raton: Lewis Wetlands International Publishers. http://www.wetlands.agro.nl 28