GNR 624 : Water Resources and River basin management Lesson 2 Why river basin Prof. R. Nagarajan, CSRE , IIT Bombay
GNR 624 : Water Resources and River basin management Problems for global freshwater situation • <1% of the world's water is available for agriculture and industry, drinking and domestic purposes, and energy generation and transport. Increasing competition for water among such uses is degrades the natural resources. • One-third of the world's population live in countries that are experiencing moderate to high water stress and death due to water-borne diseases. • Pollution from towns and cities, industry and agriculture directly affect water supplies for people and freshwater ecosystems • Diversion of water for agriculture and industry is destroying freshwater lakes and rivers • Currently, 54% of accessible runoff is appropriated by humans. By the year 2025, two- thirds of the world's population could be facing serious problems with water availability. 10.1 Prof. R. Nagarajan, CSRE , IIT Bombay
GNR 624 : Water Resources and River basin management • Freshwater ecosystems are the rivers, streams, lakes, ponds, groundwater, cave water, springs, floodplains, and wetlands (bogs, marshes, and swamps) that provide water for drinking, sanitation, agriculture, transport, electricity generation and recreation. • Physical alteration, habitat loss and degradation, water extraction, over- exploitation, pollution and the introduction of invasive species threaten the planet’s freshwater ecosystems and their associated biological resources. • The most threatened rivers. Instead, it captures the diverse social, hydrological, climatic and biological factors which threaten the integrity of major watersheds • Rivers suffering from existing threats and those which are relatively intact but under imminent danger from emerging threats. It is important to note that most river basins suffer from multiple threats that often compound each other. Prof. R. Nagarajan, CSRE , IIT Bombay
GNR 624 : Water Resources and River basin management • Dams and other infrastructure have caused the fragmentation of 60% of the large river systems in the world. • Only 64 of the world’s 177 large rivers ( 1,000 km and longer) remain free-flowing, unimpeded by dams or other barriers. • There are more than 45,000 large dams in over 150 countries. • About 1,500 are currently under construction. • Some 40 to 80 million people have been displaced by dams worldwide. • But not all dams are bad, it depends how and where they are built. Prof. R. Nagarajan, CSRE , IIT Bombay
GNR 624 : Water Resources and River basin management The world’s Longest rivers River name Continent Total length Nile Africa 6695 Km Amazon South America 6400 Km Yangtze Asia 6300 Km Mississippi-Missouri-Red Rock North America 5970 Km Yeisey-Angara Asia 5550 Km Yellow River Asia 5464 Km Ob’ -Irtysh Asia 5410 Km Rio Parana-ril grande South America 4500 Km Amur-shilka Asia 4416 Km Lena Asia 4400 Km Congo Africa 4374 Km Mackenzie-Peace-Finlay North America 4241 Km Mekong Asia 4200 Km Niger Africa 4180 Km Melt waters of glaciers - Rhone (France), lakes, e.g. Nile (Africa), springs, e.g. Thames (England) Regions of steady rainfall - Zaire (Africa). End at in the sea Amazon (Atlantic), the Niger (Gulf of Guinea) and the Indus, (Arabian Sea). Sometimes the mouth could be in a lake, e.g. Volga (Caspian), or in a swamp, e.g. Chari River (Lake Chad). Prof. R. Nagarajan, CSRE , IIT Bombay
GNR 624 : Water Resources and River basin management Prof. R. Nagarajan, CSRE , IIT Bombay
Most endangered rivers that affects River impacts assessed by human population are: • • dams and infrastructure, Salween • • La Plata excessive water extraction • • Danube climate change, • • Rio Grande invasive species, • • Ganges over-fishing, • • Murray-Darling pollution. • Indus • Nile • Yangtze • Mekong
GNR 624 : Water Resources and River basin management Global Water Challenges Ratio of maximum annual flow to minimum annual flow for selected rivers 15.5 MURRAY AUSTRALIA 4705.2 DARLING AUSTRALIA 54.3 HUNTER AUSTRALIA 16.9 ORANGE SOUTH AFRICA 3.9 POTOMAC USA 2.4 WHITE NILE SUDAN 2.0 YANGTZE CHINA 1.9 RHINE SWITZERLAND 1.3 AMAZON BRAZI L Prof. R. Nagarajan, CSRE , IIT Bombay
GNR 624 : Water Resources and River basin management Rivers are managed or controlled to be useful and less disruptive to human activity. • Dams or weirs may be built to control the flow, store water, or extract energy. • Levees may be built to prevent run-off of excess river water in times of flood. • Canals connect rivers to one another for water transfer or navigation. • River courses may be modified for navigation, or straightened to increase the flow rate. • Rivers have played an important and life-sustaining role in human societies for thousands of years. World's great cities sit on the bank of a great river. • It is used them as a source of water, for food, for transport, for recreation, as a source of power to drive machinery, and as a means of disposing of waste. Prof. R. Nagarajan, CSRE , IIT Bombay
GNR 624 : Water Resources and River basin management River Facts • An unsettling number of large rivers — including the Colorado, Rio Grande, Yellow, Indus, Ganges, Amu Darya, Murray, and Nile — are now so over tapped that they discharge little or no water to the sea for months at a time. • China is proceeding with a massive $60 billion project to transfer water from the Yangtze River Basin in the south to the water-short north. If completed it would be the largest construction project on Earth and would transfer 1.5 trillion cubic feet (41.3 billion cubic meters) of water per year — a volume equal to half that of the Nile River. • After enduring 19 flood episodes between 1961 and 1997, Napa, California, opted to restore the Napa River floodplain for $366 million, instead of the more conventional flood-control strategy of channelizing and building levees. Prof. R. Nagarajan, CSRE , IIT Bombay
GNR 624 : Water Resources and River basin management M ain threats to river basins Construction of large dams and physical alterations of river flow by straightening and deepening. River course disrupt the natural flooding cycles, reduces flows, drains wetlands, cuts rivers off from their floodplains, and inundates riparian habitats, resulting in the destruction of species, the intensification of floods and a threat to livelihoods in the long term. Deforestation and loss of natural habitats including wetlands for urban, industrial or agricultural use reduces natural flood control and destroys the habitats used by fish, water birds’ breeding, feeding and migrating. Excessive water abstraction for agricultural irrigation, domestic consumption and urban/industrial use involve pumping too much water from underground supplies, or long distance transfers of water from one basin to a neighbouring river basin result in dried-up river beds and wetlands. Ecological and economic value of freshwater systems damaged or destroyed by such technical fixes are not taken properly into account. Pollution is caused by runoff from agricultural chemicals, poorly-managed / out-of-date industrial processes, and lack of adequate treatment for sewage and other urban waste. This results in water unfit to drink, massive fish kills, and loss of underwater plants. Long-term changes in rainfall, river flow and underground water supplies due to climate change aggravates the short-sighted land-use planning that affects all sectors of human society. The rate and scale of these impacts are only set to grow. Prof. R. Nagarajan, CSRE , IIT Bombay
GNR 624 : Water Resources and River basin management Threats to rivers • Salween (ASIA) faces heavy threat from damming , the Danube (Europe) from navigation infrastructure, and La Plata (South America) from both. • Rio Grande (USA) and the Ganges face very similar problems from over-extraction for increasing irrigation and domestic consumption. • Indus faces threat from climate change because of its high dependency on glacier water. The Nile basin is very sensitive to increases in temperature because of its high rate of evaporation. • Invasive species is a plant or animal that is intentionally or unintentionally introduced to a region in which it did not naturally evolve, and where in its new environment, it grows to out-compete native species and communities. Murray-Darling (Asia-Pacific) • Mekong (Asia), the importance of fisheries for human subsistence cannot be understated, but this naturally bountiful resource is not being managed for future use. • Freshwater ecosystems naturally filter and purify water. However, this ability is impaired by excessive pollution and habitat degradation (Yangtze (Asia) Prof. R. Nagarajan, CSRE , IIT Bombay
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