New Internationalist Issue 273
Rivers - The Facts
For centuries the great river systems of the South have watered the fields, put fish on the table and acted as avenues of communication with the outside world. Their importance gives them a crucial place in the cosmology of myth and religion. But now rampant industrialism has brought competing demands that threaten both traditional ways of life and the river eco-systems themselves.
Eco-system: The longest river in the world. The Blue Nile rises in the Ethiopian highlands and the White Nile flows out of Lake Victoria through the tropical plains of Southern Sudan and the great Sudd swamps. They join together just north of the Sudanese capital of Khartoum and their combined flow survives the arid journey through the Nubian and Arabian deserts to the Mediterranean. Almost all Egyptians live clustered close to the Nile's banks.
Threats: The Aswan High Dam - one of the world's largest - has proved a mixed blessing. One gallon in five of the Nile's water evaporates from Lake Nasser behind the dam. Lack of silt and improper drainage in downstream fields means serious problems with water-logging and salination. Dependable water supplies mean new agricultural production but often for thirsty export crops like cotton. Sea erosion and lack of silt have reduced the Nile's fertile delta and the river is now a mere trickle at its mouth.
Eco-system: The largest river in the world in volume of water and drainage area and one of the world's widest, varying between 6 and 10 kms. Originating in Peru, it carries 1,000 million tons of sediment a year into the Atlantic Ocean in Brazil and the patch of brown at its mouth can be seen darkening the South Atlantic in satellite photos. Vast reaches of the Amazon basin are still essentially unmapped and little-known.
Threats: Massive logging campaigns have dramatically increased erosion and caused international concern that rainforest destruction will contribute to ozone depletion and global warming. While the slow-flowing Amazon has been saved from dam construction, Brazil's official 'Plan 2010' envisages 80 dams on its tributaries. Dams like the Balbina on the Vartna are flooding arable lands, uprooting inhabitants and adding to rainforest destruction. Watershed stability is threatened by clear-cutting for cattle rearing. 4
Eco-system: Known as the 'Long River' or 'The River of Golden Sand', the Yangtze is the longest river in Asia. It rises in the Tanglha mountains very near Tibet and flows through Szechwan and Hunan to enter the Yellow Sea near Shanghai. Some of its 600 million annual tons of mud and silt gets deposited on its fertile delta and Chongming Island at the river's mouth. The Yangtze has 700 tributaries and its drainage basin covers 20% of China's total land area.6 One in 13 people on the planet live in its basin.
Threats: The Yangtze's dangerous floods have drowned 300,000 people this century alone. For centuries a system of dikes held back floods - some as ancient as the eighth century are still in working order. The Three Gorges Dam will be the world's biggest and is projected to control flooding and provide energy-inefficient Chinese factories with hydro-power. It will cost $20 billion, take 20 years to build and flood a million people from their homes. Some 300,000 farmers will lose their land and controversies rage on the dam's effectiveness in controlling floods and long-term social and ecological costs.
Eco-system: The Ganges rises in the Himalayan glaciers in the mountainous region of the north Indian state of Uttar Pradesh. It flows 2,480 kms through India to enter the Bay of Bengal where it forms one of the world's largest deltas made up of Bangladesh and the Indian state of West Bengal. The width of its flood plain varies between two and eight kms.5
Threats: The waters of the Ganges are considered sacred in Hindu mythology, but are nonetheless heavily polluted, partly from the 40,000 people cremated yearly at Benares, but mainly from the distilleries, refineries, chemical factories and fertilizer complexes along the banks, especially at the city of Kanpur. Earthquake danger due to over-damming endangers over 100 villages and the town of Hardwar.5 Large-scale irrigation projects started a century ago and 500 new ones in the last 40 years have displaced millions of poor farmers and altered the volume speed and silt load of the river's flow.
Eco-system: The source of the Zaire (meaning river) is the Lualaba river which rises in the Zairian province of Katanga near the Zambian border. It heads north, then west, then south swallowing river after river in its rush to discharge 1.4 million cubic feet per second into the Atlantic Ocean. The banks of the Zaire are heavily forested and its relatively slow and navigable course is punctuated by wild rapids at the Porte d'Enfer and the Stanley and Inga Falls.6 The Zaire has long been an African trade and communications route, home to several pre-colonial kingdoms like the Luba inland and the Kongo near the coast.
Threats: Despite the Inga dam and power site and some localized pollution the Zaire is largely unaffected by industry. Overfishing is a potential problem. But blueprints to divert a massive amount of flow north into the Sahel to solve drought problems there have the support of Zaire's President Mobutu. This would be one of the largest-ever water diversions - in one version carrying 100 cubic kilometres of water annually (more than the flow of the Nile). The developmental and ecological problems of cutting the Zaire's flow and transporting the fish, insects and diseases of tropical rainforest into a semi-arid desert are unimaginable.
Down the Drain
Global water use has tripled since 1950 to 4,340 cubic kms - 8 times the annual flow of the Mississippi. Some 65% of this is used in agriculture.
More than 10% of the world's irrigated land suffers from yield-suppressing salt build-up which is spreading at the rate of 1.5 million hectares a year. Currently less than 40% of water used in irrigation ends up benefiting crops.3
Engineers have now built 36,000 dams worldwide. Construction continues at the rate of 170 dams a year. An estimated 1% of dam capacity is lost every year as reservoirs become clogged with a million tons of silt (about 10% of global river discharge). This fertile silt is also lost to downstream farmers.4
Farmers could cut water use by 10-50%, industry by 40-90% and cities by 1/3 with no sacrifice to economic output or quality of life.3
1 Times Atlas of the World (1985).
2 Encarta '95 (Microsoft).
3 Last Oasis Sandra Postel (WW Norton, New York 1992).
4 The Dammed Fred Pearce (Bodley Head, London 1992).
5 The Ganges: Great Rivers of the World George F Mobley (National Geographic 1984).
6 Encyclopaedia of the World's Great Rivers (Rand-Macnally, New York, 1980).
©Copyright: New Internationalist 1995
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