Major Water Bodies of Africa and Asia
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This document provides information on various lakes and water sources around the world through images showing changes over time. It discusses factors like population growth, dam construction, irrigation, and climate change that have impacted bodies of water. Examples shown include the shrinking of Lake Chad and Aral Sea, flooding from dams in Nigeria and Mozambique, and invasive species problems in Lake Victoria and Chivero. The document emphasizes that many lakes and rivers are facing threats from water diversion for agriculture and cities and calls for sustainable management of freshwater resources.
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Major Water Bodies of Africa and Asia
- 3. • Lake Chad, Nigeria, Niger, Chad, Cameroon • Challawa Gorge Dam, Nigeria • Lake Nakuru, Kenya • Lake Victoria, Uganda • Lesotho Highlands Water Project, Lesotho • Aral Sea, Kazakhstan • Lake Balkhash, Kazakhstan • Kara- Bogaz -Gol (KBG), Turkmenistan WATER AND LAKES Estimated global water loss in irrigation Source: FAO
- 4. • Dead Sea, Jordan • Lake Hamoun, Iran • Mesopotamia Marshlands, Iraq • Three Gorges Dam, China • Atatürk Dam, Turkey • Gabcikova, Slovakia • Lake Chapala, Mexico • Everglades, United States WATER AND LAKES Three Gorges Dam, October 24, 2003: Digital Globe
- 5. WATER FACTS • Demand for and use of freshwater has tripled over the past half century, as world population has grown from 2.5 to 6.45 billion people Sources: Asian Development Bank; BBC; Earth Observatory; UNEP; UNESCO • Of the 0.5% useable freshwater, irrigation accounts for 70%, industry 20% and household 10% • Experts predict that by 2025 global water needs will increase with 40% more required for cities and 20% for growing crops • The satellite photos show major freshwater depletion taking place on all continents, notably in the Dead Sea, the Aral Sea, Lake Chad, the Mesopotamian Marshlands, the Everglades and other water sources • According to UNESCO estimates, by 2030 global demands for fresh water will exceed the supply with potentially disastrous consequences • Of total world water, 97.5% is salty water and only 2.5% is freshwater of which useable freshwater accounts for about 0.5%
- 6. WATER FACTS • Water withdrawals are causing major rivers—such as the Colorado, the Nile, the Yellow Rivers—to run dry, lakes to vanish and groundwater tables and aquifers to drop almost everywhere • In 2002, around 3.16 billion people (82%) in the Asia Pacific region had access to improved water supplies, up from 74% in 1990 Sources: Asian Development Bank; BBC; Earth Observatory; UNEP; UNESCO • Over the next 20 years, average water supply per person is estimated to drop by a third, endangering human health, agriculture and the environment • Water pollution is a serious threat to the world’s water supply • Water volume in the Aral sea has dropped by about 80% since 1960s, due to extensive irrigation primarily for cotton production • Current water levels in Lake Victoria are below normal and the lowest level since September 1961
- 7. Shrinking Lake Chad Nigeria, Niger, Chad, Cameroon Persistent drought has shrunk the lake to about a tenth of its former size • 1972: Larger lake surface area is visible in this image • 2001: Impact of drought displays a shrunken lake, comparatively much smaller surface area than in 1972 image
- 8. Impact of Challawa Gorge Dam, Nigeria These images show the area before and after construction of the dam. • 1990: Image of the area before the completion of the dam in 1993 • 1999: Impact of flooding upstream from the dam; colour of the water in the flooded area indicates high sediments
- 9. Land cover degradation around Lake Nakuru, Kenya These images show the land cover degradation in the lake’s catchment • 1973: The area that hosts the world’s largest concentration of flamingos • 2000: Excision of forest in the Eastern Mau Forest Reserve (white lines) will most likely lead to disappearance of upper catchment forest cover
- 10. Water hyacinth in Lake Victoria Uganda These images show water hyacinth infestation and control of such invasive species • 1995: Image shows several water-hyacinth-choked bays (yellow arrows) • 2001: A visible reduction of Water Hyacinth, after its removal from Lake Victoria, contributes to human prosperity
- 11. Population growth around Lake Victoria Uganda • The population growth around 100 km buffer zone of the Lake Victoria • Population growth around Lake Victoria, East Africa, is the highest in Africa
- 12. Fastest growing rural population around Lake Victoria, Uganda 8.57 11.71 16.05 22.13 30.51 41.80 47.23 0.00 10.00 20.00 30.00 40.00 50.00 1960 1970 1980 1990 2000 2010 2015 Total Population Total Human Population Living around Lake Victoria (millions)
- 13. 45 61 84 115 159 9 12 16 21 26 32 36 218 246 0 50 100 150 200 250 1960 1970 1980 1990 2000 2010 2015 Lake Victoria Africa Average Lake Victoria vs. Africa
- 14. Title Body text Height variation of Lake Victoria, Uganda Lake Victoria Height Variations http://www.pecad.fas.usda.gov/cropexplorer/global_reservoir/gr_regional_chart.cfm?regionid=eafrica®ion=&reservoir_name=Victoria
- 15. Title Body text Monitoring Lake Victoria, Uganda Current water levels are below normal and the lowest level since September, 1961
- 16. The Lesotho Highlands Water Project diverts water for South Africa’s urban and industrial use • 1989: Image of the area before the completion of the dam in 1995 • 2001: Katse dam created an enormous reservoir, the extent of which can clearly be seen in this image Changes due to dam construction in Lesotho Lesotho
- 17. Death of a sea - Aral Sea, Kazakhstan Images show death of the world’s fourth largest inland sea • 1973: The surface of the sea once measured 66 100 km2 • 1987: 60% of the volume had been lost • 1999-2004: The sea is now quarter of the size it was 50 years ago
- 18. Alarming drop in Lake Balkhash’s water level Kazakhstan • 1975-1979: Excessive use and waste of lake water are causes of the drop • 2001: Smaller neighbouring lakes appear to be drying up
- 19. Kara-Bogaz-Gol – Lagoon of the Caspian sea Turkmenistan Caspian Sea is the largest inland body of water in the world • 1988: KBG is the large shallow lagoon of the Caspian sea • 2000: Caspian Sea levels are higher than 1978 levels and water flows freely into salty waters of KBG
- 20. • 1973: The Sea level is dropping at the rate of 1m/year Dramatic changes in Dead Sea, Jordan Images show dramatic changes in the Dead sea over 30 years • 2002: Notice the expansion of salt works, and near-complete closing off of the southern part by dry land
- 21. Changes in water levels on Lake Hamoun Iran Changes in water levels on Lake Hamoun • 1976: The amount of water in the lake is relatively high • 1999-2001: The lake dried up and disappeared
- 22. Demise of an ecosystem – Mesopotamian Marshlands, Iraq Upstream damming as well as drainage activities in the marshlands themselves have significantly reduced the quantity of water entering the marshes • 1973-2000: Most of the wetlands disappeared
- 23. Restoration of the Mesopotamia Marshlands in Iraq • 2000: Water returns to the Mesopotamian Marshlands • 2004: Greening of some of the Marshlands in recent years
- 24. Changes due to Three Gorges Dam construction, China Changes due to the construction of dam • 1987: Nature of the river and surrounding landscape before the dam • 2004: The enormous dam is clearly visible
- 25. Changes due to Atatürk Dam, Turkey Development of Harran region is strikingly apparent in these images Right-hand corner of the 1999 image shows irrigated fields surrounding the town of Harran The dam provides power and irrigation water
- 26. Damming around Gabcikova, Slovakia 1973-2000: Images show changes brought about by massive re-channeling of river water
- 27. Country’s largest natural lake - Lake Chapala Mexico • 1983: Level of the lake has declined; noticeable decreases in wetlands • 2001: Alteration in the contours of the shoreline is clearly visible
- 28. Urban encroachment in Florida’s Everglades United States • 1973: Rapid urban expansion has converted farmlands to cityscapes • 2002: Existence of vast wetlands “Everglades” threatened by urban encroachment
- 29. • Lake Kivu, Congo/Rwanda • Lake Alaotra, Madagascar • Lake Al Wahda, Morocco • Lake Cahora Basa, Mozambique • Lake Chivero, Zimbabwe • Lake Djoudj, Senegal • Lake Ichkeul, Tunisia • Lake Manantali, Mali • Lake Sibaya, South Africa • Songor Lagoon, Ghana • Lake Tonga, Algeria WATER AND LAKES
- 30. LAKE FACTS • According to the WORLDLAKE database, there are 677 lakes in Africa • There are 15 natural lakes that cross the political boundaries of two or more countries in Africa • Lake Chad’s surface area has shrunk by 95 per cent over the past 35 years • There are 60 transboundary river basins in Africa, covering over 63 per cent of the continent’s land area Sources: UNEP 2006 • Uncontrolled damming, the withdrawal of water for irrigation, and climate variability are the major causes of drying up of Lake Tonga in Algeria • Population growth around Lake Victoria, the continent’s largest lake, is significantly higher than the rest of Africa • Some lakes in central Africa have become known as “killer lakes,” because of the catastrophic natural events that have occurred in their vicinity
- 31. Lake Kivu-one of Africa’s “killer lakes” Congo/Rwanda These images show dramatic changes before and after the eruption of Mt. Nyiragongo in 2002 • 2001: Before the January 2002 eruption • 2003: Shows the track of the lava flow
- 32. Severe flooding around Lake Alaotra Madagascar These images show flooding over a wide area • Flooding destroys significant portion of crops • Intensive rice irrigation occurs at the western part of the lake (yellow arrows)
- 33. Impact of Al Wahda reservoir in Morocco These images illustrate the change in land cover • 1987: The area before the construction of dams • 2001: The area after the construction of 110 large dams
- 34. Cahora Basa – Mozambique’s largest dam on the Zambezi River These images show spectacular changes in the Zambezi riverine system • 1972: The Zambezi River a few years before the dam construction • 1999: This image shows part of the enormous dam and the lake
- 35. Invasive water weeds in Lake Chivero, Zimbabwe These images show overall reduction in water weeds • 1989: Weeds show up as green strands along the edges of the lake • 2000: This image shows that water weeds remains a persistent problem
- 36. Rejuvenation of the Djoudj Sanctuary in Senegal These images show the Djoudj Sanctuary before and after the construction of the Diama Dam • 1979: Shows the impact of drought on the Djoudj Sanctuary • 1999: Rejuvenation of the Sanctuary wetlands due to significant floods
- 37. Ecological changes around Lake Ichkeul, Tunisia These images show the impact of damming • 1972: Shows the three feeder rivers supplying the lake before they were dammed • 2000: Shows the location of the dams (yellow arrows)
- 38. Agricultural expansion around Lake Manantali, Mali These images show the expansion of irrigated agriculture • 1977: Shows the original meandering nature of the Bafing River • 1999: Shows the expanded irrigated land and increase in lake water quantity
- 39. Lake Sibaya – wetland of international important in South Africa These images show increase in cultivation around the lake • 1991: Lakeshore is home to the only known species of a rare climbing orchid • 2001: The yellow arrows vividly show the increase of cultivation of marginal lands around the lake
- 40. Reduction in the surface area of Songor Lagoon, Ghana These images show a conspicuous reduction in the surface area • 1990: Shows major lagoon system associated with Volta river estuary • 2000: This image shows water area dramatically reduced, exposing bare ground
- 41. Changes in and around Lake Tonga Algeria These images show the changes brought about by damming of the feeder rivers • 1988: Lake Tonga before the damming of feeder rivers • 2000: Damming increased irrigation and drastically reduced the volume of water entering the lake
- 42. One Planet Many People: Atlas of Our Changing Environment Thank You! Free Downloads: www.na.unep.net Purchase: www.Earthprint.com WATER
Editor's Notes
- The most sacred Hindu river, the Ganges, is so depleted that the Sundarban wetlands and mangrove forests of Bangladesh are seriously threatened. It is also said to contain unacceptable levels of arsenic. As more trees are chopped down, and more buildings erected along its banks, the glaciers supplying the river have been melting, raising fears of shortages and drought downstream. The river has been the subject of a long-running dispute between India and Bangladesh, although recently progress has been made in resolving the conflict. The Aral Sea in Central Asia was once the world's fourth biggest inland sea, and one of the world's most fertile regions. But economic mismanagement has turned the area into a toxic desert. The two rivers feeding the sea, the Amu Darya and the Syr Darya, were diverted in a Soviet scheme to grow cotton in the desert. Between 1962 and 1994, the level of the Aral Sea fell by 16 metres. The surrounding region now has one of the highest infant mortality in the world, and anaemia and cancers caused by chemicals blowing off the dried sea bed are common. water volume has dropped by about 80% due to extensive irrigation
- The most sacred Hindu river, the Ganges, is so depleted that the Sundarban wetlands and mangrove forests of Bangladesh are seriously threatened. It is also said to contain unacceptable levels of arsenic. As more trees are chopped down, and more buildings erected along its banks, the glaciers supplying the river have been melting, raising fears of shortages and drought downstream. The river has been the subject of a long-running dispute between India and Bangladesh, although recently progress has been made in resolving the conflict. The Aral Sea in Central Asia was once the world's fourth biggest inland sea, and one of the world's most fertile regions. But economic mismanagement has turned the area into a toxic desert. The two rivers feeding the sea, the Amu Darya and the Syr Darya, were diverted in a Soviet scheme to grow cotton in the desert. Between 1962 and 1994, the level of the Aral Sea fell by 16 metres. The surrounding region now has one of the highest infant mortality in the world, and anaemia and cancers caused by chemicals blowing off the dried sea bed are common. water volume has dropped by about 80% due to extensive irrigation
- Lake Chad, located at the junction of Nigeria, Niger, Chad, and Cameroon was once the sixth-largest lake in the world. Persistent droughts have shrunk it to about] a tenth of its former size. The lake has a large drainage basin—1.5 million km2 (0.6 million square miles)—but almost no water flows in from the dry north. Ninety per cent of lake’s water flows in from the Chari River. The lakebed is fl at and shallow; even before the drought, the lake was no more than 5-8 m (16-26 ft) deep. Considered a deep wetland, Lake Chad was once the second largest wetland in Africa, highly productive, and supporting a diversity of wildlife. The lake is very responsive to changes in rainfall. When rains fail, the lake drops rapidly because annual inflow is 20-85 per cent of the lake’s volume. Human diversion from the lake and from the Chari River may be significant at times of low flow, but rainfall is still the determining factor in lake level. This image set displays a continued decline in lake surface area from 22 902 km2 (8 843 square miles) in 1963 to a meager 304 km2 (117 square miles) in 2001.
- The Challawa Gorge Dam, completed in 1993 on the Challawa River, is the second-largest of the 23 dams along rivers in Nigeria’s Hadejia-Jama’are River Basin. Though the dam has improved the water supply for irrigation, heavy rains cause the river to break its banks upstream from the dam; farmers are driven out as the rising water floods their farms and adjoining lands. Areas downstream from the dam, on the other hand, do not receive enough water to maintain the wetlands that border the river. Under these conditions, the soil dries out and overgrazing occurs, which in turn leads to wind erosion of the topsoil. This satellite image pair gives a comparison of the area before and after construction of the dam. The 1999 image shows the degree to which flooding upstream from the dam impacts the landscape, and how the lack of water downstream negatively affects riverine wetlands and cropland. The colour of the water in the flooded area is also indicative of high-sediment content.
- Lake Nakuru is located in the Eastern Rift Valley in southwest Kenya. Lake Nakuru National Park is the second most visited protected area in Kenya. It hosts the world’s largest concentration of flamingos, as well as many of the animal species that make Kenya a highly valued tourism destination, including lions, leopards, rhinoceros, and water buffalo. In its total area of 188 km2 (73 square miles), there are over 450 bird species and 56 mammal species. Recognized as a wetland of international importance, Lake Nakuru was declared a Ramsar Site in 1990. The threat of land cover degradation in the catchments of the lake is likely to increase flow fluctuation and decrease water quality. These images show the land cover degradation in the lake’s catchment between 1973 and 2000. In 2001, the Government of Kenya announced its intention to excise 353 km2 (136 square miles) of forest in the Eastern Mau Forest Reserve (area with white boundary in the 2000 image). As a result, most of the forest cover in the upper catchment of the main rivers that feed Lake Nakuru will disappear.
- Shared by Kenya, Tanzania, and Uganda, Lake Victoria is the second largest freshwater lake in the world. The infestation of Lake Victoria by water hyacinth in the 1990s disrupted transportation and fishing, clogged water intake pipes for municipal water, and created habitat for disease-causing mosquitoes and other insects. This led to the initiation of the Lake Victoria Environmental Management Project in 1994. The focus of the Project was to combat hyacinth infestations on the lake, particularly the region bordered by Uganda, which was one of the most severely affected areas. The 1995 image shows several water-hyacinth-choked bays: Murchison Bay near Gaba; large parts of Gobero and Wazimenya Bays; an area outside Buka Bay; and near Kibanga Port (yellow arrows). Initially, water hyacinth was controlled by hand, with the plants being manually removed from the lake. But re-growth quickly occurred. A more recent control measure has been the careful introduction of natural insect predators of water hyacinth. As the 2001 image shows, this approach seems to have been successful, as the floating weeds have disappeared from all the locations noted above.
- Population growth around Lake Victoria, is significantly higher than in the rest of Africa because of the wealth of natural resources and economic benefits the lake region offers. Note the increase in population in a 100-km (62 miles) buffer zone around Lake Victoria between 1960 and 2000. During each decade, population growth within this zone outpaced the continental average.
- The Lesotho Highlands Water Project (LHWP) is one of the largest infrastructure projects ever undertaken on the African continent. The project is designed to divert water from Lesotho’s Maloti Mountains to South Africa’s urban and industrial Gauteng Province. While South Africa is set to benefit from an increased supply of much-needed water, Lesotho would gain through the generation of hydroelectric power and profits from the sale of water. An 82-km (51-mile) water transfer-and-delivery system is already in place for delivering water to South Africa. On completion of the full project, a total of four dams will be placed in key locations. However, many questions remain unanswered about the social and environmental impacts the completed dams will have. The first dam in the multi-dam scheme, called Katse, located on the Orange River, closed its gates in 1995, creating an enormous reservoir along with serious social and environmental concerns. These two images provide a comparison of the area before and after completion of the Katse dam. The effects and extent of the Katse Dam can clearly be seen in the 2001 image.
- The name “Aral Sea “ comes from the word “aral” meaning island. The sea’s name reflects the fact that it is a vast basin that lies as an island among waterless deserts. The Aral Sea was once the world’s fourth-largest inland sea. Its problems began in the 1960s and 1970s with the diversion of the main rivers that feed it to provide for cotton cultivation in arid Soviet Central Asia. The surface of the Aral Sea once measured 66 100 km2 (25 521 square miles). By 1987, about 60 per cent of the Aral Sea’s volume had been lost, its depth had declined by 14 m (45 feet), and its salt concentration had doubled, killing the commercial fishing trade. Wind storms became toxic, carrying fi ne grains of clay and salts deposited on exposed sea floor. Life expectancies in the districts near the sea are significantly lower than in surrounding areas. The sea is now a quarter of the size it was 50 years ago and has broken into two parts, the North Aral Sea and the South Aral Sea. Re-engineering along the Syr Darya River delta in the north will retain water in the North Aral Sea, thereby drying the South Aral Sea completely, perhaps within 15 years.
- Located in Kazakhstan, Central Asia, Lake Balkhash is replenished from the Ili River catchment area, most of which is located in northwestern China. The lake is a very important resource for the surrounding population. Water from the lake and its tributary rivers is used for irrigation and both municipal and industrial purposes, including supplying the water needs of the Balkhash Copper Melting Plant. Lake fish are also an important food source. However, artificially low water prices have encouraged excessive use and waste of lake water. The United Nations has warned that Lake Balkhash, which is the second largest lake in Central Asia after the Aral Sea, could dry up if current trends are not reversed. These two satellite images reveal an alarming drop in the lake’s water levels in just over twenty years. Smaller, neighboring lakes, to the southeast of Balkhash, have become detached from the main water body; they have dramatically decreased in size and appear to be drying up.
- The Caspian Sea, seen in this 2004 image, is the largest inland body of water in the world, often categorized as a large salt lake. It is salty because rivers (especially the Volga) flow into it, but none flow out. Water leaves through evaporation, and the dissolved salts remain. Changes in water levels are common in the sea, resulting both from changing climatic factors and water diversion by humans. The 2004 image highlights the area of change—the Kara-Bogaz-Gol (KBG). KBG is a large, shallow lagoon of the Caspian Sea, normally about 18 200 km2 (7 000 square miles) and a few metres deep. The Caspian’s changing water level has been a concern since the 1970s. The KBG’s water flows in from the Caspian Sea, and its fluctuations have affected the KBG dramatically. In the 1980s, a dam blocked the KBG’s inflow, resulting in the formation of a “salt bowl” that caused widespread problems of blowing salt, reportedly poisoning soil, and causing health problems for people living hundreds of kilometers downwind to the east. While the dam was in place, not only did the KBG’s water level rapidly drop by 2 m (7ft) or more, but the lagoon’s shallow bottom also rose 0.5 m (2 ft), due to the accumulation of salts. The dam was partially opened in 1985, and completely opened in 1992 when Caspian Sea water levels started to rise quickly. Today, sea levels are more than 2.6 m (9 ft) higher than the 1978 levels and water flows freely into the salty waters of the Kara-Bogaz-Gol.
- For decades, heavy demands have been placed on the land-locked Dead Sea to meet the needs of growing populations in the countries that border it. Both Israel and Jordan draw water from rivers that flow into the Dead Sea, reducing the amount of water that would naturally replenish it. The amount of area devoted to evaporation ponds for producing salt has greatly expanded over the past three decades. The creation of salt works tends to accelerate evaporation, further contributing to the reduction in water level. Currently, it is estimated that the water level of the Dead Sea is dropping at a rate of about one metre (3 feet) per year. These two images, from 1973 and 2002, reveal dramatic changes in the Dead Sea over a period of about 30 years. Declining water levels, coupled with impoundments and land reclamation projects, have greatly increased the amount of exposed arid land along the coastline. The near-complete closing off of the southern part of the Sea by dry land (2002 image) reveals the severity of water level decline.
- Iran’s Lake Hamoun is fed primarily by water catchments in neighboring Afghanistan. In 1976, when rivers in Afghanistan were fl owing regularly, the amount of water in the lake was relatively high. Between 1999 and 2001, however, the lake all but dried up and disappeared, as can be seen in the 2001 satellite image above. The “dry phase” of Lake Hamoun is a striking example of how competition for scarce water resources can transform a landscape. When droughts occur in Afghanistan, or the water in watersheds that support Lake Hamoun is drawn down by other natural or human-induced reasons, the end result is a dry lakebed in Iran. In addition, when the lake is dry, seasonal winds blow fine sands off the exposed lakebed. The sand is swirled into huge dunes that may cover a hundred or more fishing villages along the former lakeshore. Wildlife around the lake is negatively impacted and fisheries are brought to a halt. Changes in water policies and substantial rains in the region saw a return of much of the water in Lake Hamoun by 2003.
- Located at the confluence of the Tigris and Euphrates rivers, the Mesopotamian marshlands are one of the world’s great wetlands covering an estimated original area of 15 000 - 20 000 km2 (5 792 - 7 722 square miles) The marshlands are an important center of biodiversity, play a vital role in the intercontinental migration of birds, and have long supported unique human communities. Upstream damming as well as drainage activities in the marshlands themselves have significantly reduced the quantity of water entering the marshes. Together these factors have led to the collapse of the ecosystem. Restoration of the marshlands, mainly through reflooding by breaching of dykes and drainage canals has begun. As a result of these activities, vegetation and wildlife have returned to some parts of the marshes. This set of images provides a synoptic illustration of the changes. While the 1973 image (inset left) shows the extent of the original marshlands, the 2000 image (inset right) reveals the area after being drained, with most of the wetlands having disappeared. On the other hand, the 2004 image illustrates recovery in progress with major portions in the central and western sections having been restored to some extent.
- The Three Gorges Dam on the Chang Jiang (Yangtze) River in China is one of the largest single construction projects ever attempted on the planet. The dam was constructed to supply approximately one-ninth of China’s electricity—as much power as could be generated by at least fifteen nuclear power plants. It is a relatively environmentally clean option compared to coal burning or nuclear power plants. It is also hoped that the dam will help control flooding on a river where seasonal floods during the past century has caused death of over one million people. However, the Three Gorges Dam project has also had negative environmental and social impacts as a result of the massive construction efforts and the submergence of land along the river above the dam. The former village of Zigui (top center of image) has already been submerged. The 1987 image shows the nature of the river and surrounding landscape before work on the dam was begun. In the May 2004 image, the enormous Three Gorges Dam is clearly visible, as is the reservoir of impounded river water that has been created behind it.
- Built in 1990, the Atatürk Dam on the Euphrates River in southeastern Turkey is the centre piece of the Southeastern Anatolia Project. The Atatürk Dam is the largest in a series of 22 dams and 19 hydroelectric stations built on the Euphrates and Tigris Rivers in order to provide irrigation water and electricity to this arid region of the country. When the project’s entire system of reservoirs, power generation stations, and irrigation channels is operational (projected to occur in 2010), the irrigation of approximately 1.7 million hectares (4.2 million acres) of land will be possible.. In these two Landsat images, acquired in 1976 and 1999, respectively, the transformation of the region around the dam is strikingly apparent. The dam’s reservoir reached capacity in 1992 and has supplied sufficient water for irrigation to turn a once-arid landscape into a green one. This is especially obvious in the lower right-hand corner of the 1999 image, where irrigated fields completely surround the town of Harran. The development of the Harran region could not have occurred without the Atatürk Dam project, especially since the town is many kilometres from the river.
- The Gabcikova-Nagymoros hydraulic project on the Danube River was started in order to generate electric power, create an inland waterway, help manage water supplies, and aid in the region’s economic development. The river was to be dammed and its water diverted into a canal. Four decades after it was initiated the Cunovo Dam began operation in Slovakia in October 1992. The dam diverted 80 to 90 per cent of Danube River water down a diversion canal to support a hydroelectric power station. This pair of images from 1973 and 2000 reveals the striking changes the massive re-channeling of river water has brought to the region. The dam altered the hydraulic regime of the Danube River valley from a natural waterway to a controlled patchwork of channels and islands. The diversion of water by the dam brought an end to the natural, beneficial flooding that added moisture and nutrients to the soil. It also reduced the ability of wetlands and marshes to filter surface water and trap sediments. Consequently, water quality and soil nutrients levels in the region have declined. Generation of electricity has come with significant environmental cost.
- Mexico’s Lake Chapala, lying in the heart of an extremely arid region, is the country’s largest natural lake. The lake is one of the most important wetlands in the region and home to more than 70 endemic species. Since the 1950s, Lake Chapala has undergone many changes as a result of water abstraction for agricultural use both inside and outside the region and for a rapidly growing population. The level of the lake has declined, and there have been noticeable decreases in surrounding wetland areas as well as changes in the hydrological system connecting various springs. Some of these changes are visible in this pair of satellite images, including alterations in the contours of the shoreline, obvious extensions of land near various townships around the lake, and the appearance of remarkably large areas of reclaimed land at the lake’s eastern end. Like all arid areas, the land around Lake Chapala is prone to salinization. If the lake continues to shrink, researchers predict both a decrease in water availability and an increase in the salt content of the region’s soil.
- These two Landsat images of southern Florida in the United States reveal some of the changes that have occurred in this region over the past 30 years. One of the most obvious is the growth of the Fort Lauderdale- Miami urban area. Urban version of what were once farmlands to cityscapes. The city of Miami has also expanded greatly to the southwest. The advance of urban areas westward across the peninsula threatens the continued existence of the vast wetlands area known as the Everglades. The Everglades ecosystem naturally filters groundwater and helps to recharge the Biscayne Aquifer. It is also home to a remarkable collection of plants and animals for which southern Florida is famous. As urban areas encroach upon the Everglades, water resources and wildlife habitat are placed at serious risk. Protecting the Everglades to maintain its essential water filtering capacity and remarkable biodiversity is part of the mission of the Federal “Smart Growth” Task Force, which is working to better manage urban sprawl and its negative consequences.
- Lake Kivu on the Congo-Rwanda border is the highest lake in Africa at 1 459 m (4 788 ft). Beneath the lake lie vast reserves of methane gas which has not been exploited. Lake Kivu is also an important tourist center. These satellite images of Lake Kivu show dramatic changes before and after the eruption of Mt. Nyiragongo in January 2002. The 2003 image clearly shows the track of the lava flow, which traveled through Goma town and into the northeastern part of the lake, contaminating its waters. Lake Kivu is one of Africa’s “killer lakes,” containing a volatile combination of methane and carbon dioxide gases with the capacity to kill thousands of people.
- Lake Alaotra is a shallow, reed-fringed lake that lies in a tectonic basin 40 km (25 miles) long and 9.5 km (6 miles) wide. The images from March 2005 show extensive flooding of the lake, especially along its western and southern shores. Heavy rains, unusual for the time of year, caused severe flooding across Madagascar, destroying an estimated ten per cent of the region’s rice crop. This pair of MODIS images shows flooding over a wide area, including Lake Alaotra (outlined in white). In the images, vegetation shows as bright green, water as shades of blue, and clouds as light blue. Intensive rice irrigation occurs at the western part of the lake (yellow arrows).
- The center of the Kingdom of Morocco is occupied by the high Atlas Mountains which separate fertile coastal plains from inland pre-Saharan semi-arid areas. In Morocco, the rain rate varies strongly from one region to the other, when going southward or eastward. To reduce the effects of that disparity, Morocco has adopted a policy for transferring water from regions with surplus towards regions with water deficits. The dam policy initiated at the beginning of the 1960s has had beneficial fallouts for social and economic development of the country. There are now 110 large dams in Morocco, with a storage capacity of 158 000 millions of m3. These two satellite images illustrate the change in land cover before and after the Al Wahda reservoir was constructed.
- Cahora Basa Reservoir in Tete Province of Mozambique is the site of the country’s largest dam on the Zambezi River. These satellite images show spectacular changes in the Zambezi riverine system over the past three decades. The 1972 image shows the Zambezi River a few years before the Cahora Basa Dam was constructed, while the 1999 image shows part of the enormous dam and the lake. The eastern/right tip of the river is visible in both images, entering into a narrow gorge, which provides an obvious location for a power-producing barrage (dam) of this size. Although the construction of Cahora Basa was seen as a strategic move to meet the region’s growing energy needs, it has also reduced the extent of annual flooding on the Zambezi River downstream—in turn reducing the size of the floodplains on which local communities grow their crops.
- Lake Chivero holds about 250 000 million litres (264 000 million quarts) of water and is approximately 26 km2 (10 square miles) or 2 632 ha. Beginning in the mid 1980s, the lake became progressively eutrophic, after a recovery period from a previous eutrophication phase in the mid 1960s. While these two images suggest an overall reduction of the presence of invasive water weeds in Lake Chivero between 1989 and 2000, there is evidence that this remains a persistent problem. The weeds show up as green strands along the edges of the lake. Like most of Zimbabwe’s freshwater bodies, freeing Lake Chivero from the weed menace will require long-term eradication strategies, continuous monitoring, and a comprehensive integrated water basin management programme.
- Situated in the Senegal River delta, the Djoudj Sanctuary is a wetland of 16 000 ha, comprising a large lake, referred to as Lake Djoudj in this publication, surrounded by streams, ponds and backwaters. These two images show the Djoudj Sanctuary before and after the construction of the Diama Dam. The image from September 1979 shows the impact of drought on the Djoudj sanctuary, while the image from November 1999 shows rejuvenation of the sanctuary wetlands due to the signifi cant fl oods of that year. The two images vividly depict the impact of climate variability on the Djoudj Sanctuary—and demonstrate the broader need for close monitoring of the impacts of climate variability and climate change on lake environments.
- Lake Ichkeul is the last remaining lake in a chain that once extended across North Africa. The construction of three dams on rivers supplying Lake Ichkeul and its marshes has cut off almost all inflow of fresh water, causing a destructive increase in the salinity of the lake and marshes. The 1972 image shows the three feeder rivers supplying the lake before they were dammed. The 2000 image shows the location of the dams (yellow arrows) built to increase irrigation and water supplies to local communities. However, the decreasing water discharge into the lake caused by the damming lead to prolonged drought of the surrounding marshlands. Changes to the prevalent vegetation and other serious ecological changes have inevitably led to a decrease in the number of birds using the lakeshores as a breeding site.
- Lake Manantali on the Bafing River contributes to power generation and irrigation in the surrounding areas. These two images illustrate some of the physical changes that have occurred in the Bafing riverine system since the construction of the Manantali Dam, which began in 1981. The 1977 image shows the original meandering nature of the Bafing River, which annually deposited rich fluvial soils used by local people for growing sorghum and other crops on its floodplains. The 1999 image shows the extent of irrigated agriculture in the surrounding area, which rapidly expanded after the dam was filled between 1986 and 1988. The increase in water quantity is also clearly visible in 1999 image.
- Lake Sibaya is narrowly separated from the sea by a range of high forested coastal dunes. The lake is home to large hippopotamus and crocodile populations, although their numbers have dropped over the last fifteen years due principally to poaching. The lakeshore is also home to the only known population of a rare climbing orchid. The yellow arrows vividly show the increase in cultivation of marginal lands around Lake Sibaya. Agriculture in the lake catchment and along its drainage lines may cause erosion, eutrophication, pollution, and the drying up of wetlands around the lake raising concerns among environmentalists. Although Lake Sibaya has been designated a wetland of international importance, there has been little effort by communities around the lake to practice sustainable management or to protect the rare species found in the region.
- Songor Lagoon is one of the major lagoon systems, associated with the Volta river estuary, with a surface area of about 115 km2 (44 square miles). These two images show a conspicuous reduction in the surface area of Songor Lagoon—and the environmental health of the wider region. The deep blue open-water area is dramatically reduced in the 2000 image, with large areas of bare ground exposed. Although some of these changes may reflect seasonal or annual rainfall variability, closer analysis indicates a more permanent and significant decline in the lagoon’s surface area. The two main reasons for this appear to be salt extraction at the western end of the lagoon and diversion of feeder streams for irrigation.
- These two images show the dramatic human induced changes in and around Lake Tonga over the past 15 years. The damming of the feeder rivers of Lakes Tonga and Oubeira (shown in the bottom part of the 2000 image) has resulted in increasing irrigation around the dams and a drastic reduction in the volume of water entering the lake. The 2000 image was acquired during the rainy season, showing an increase in the water volume after the 1999 drought, which had left the lake virtually dry. The widespread ecological changes caused by the construction of dams around Lake Tonga should serve as an eye-opener to the community. Environmental Impact Assessments of the area could assist African policymakers with information to make informed choices about future projects.