The Atlas of Water. Maggie Black
Читать онлайн книгу.
Rising Demand
More than 4,000 cubic kilometres of fresh water are withdrawn every year – equivalent to roughly 1,700 litres per person per day. Although this is more than anyone needs for personal use, even to fill their swimming pool and sprinkle their garden round the clock, a large amount of water is consumed indirectly, embedded in food and industrial products. Meat-rich diets and other attributes of a high-consumption lifestyle, such as the acquisition of cars, television sets, and goods whose manufacturing processes require water, absorb ever larger quantities. Thus, the rapid rise in demand, experienced across all categories of water use (agricultural, industrial, and domestic/municipal), is a reflection not just of an increasing global population but of changing lifestyles. Domestic use – for drinking, bathing, cleaning, – is modest compared to demand for agriculture and industry. But industrial water use, including that for hydropower, reflects people’s demand for embedded water in the form of high-class products and high-end lifestyles. Those people still living in semi-subsistence economies make the lowest demands, often using fewer than 25 litres per person per day for all purposes. Water for agriculture is by far the largest extractive category. This reflects lower demand for industrialized lifestyle items in less developed and more agrarian regions; and the dependence, in low rainfall and monsoon areas, on seasonal storage and irrigation from rivers, reservoirs and aquifers. Increasing demand for food and growing demand for energy continue to inspire heavy investment in large-scale water infrastructure, despite the costly ecological damage and human displacement entailed. Water withdrawals for irrigation are expected to increase by 5 per cent by 2050. This may sound modest, but will mainly occur in regions already suffering from water scarcity.
WORLD WATER USE
Q 3 Water Shortage
26
HOW WATER IS USED
Copyright © Myriad Editions
5 Dwindling Supply; 6 Competition and Conflict R
27
Dwindling Supply
About a fifth of water consumed globally is from underground aquifers. These are replenished by rainwater seeping through soil and rock, but many are being over-exploited. Some non-renewable “fossil water” aquifers are being irreversibly mined. In all parts of the world, groundwater is being withdrawn recklessly. The world’s four top irrigators – China, India, Pakistan and the USA – are all pumping groundwater faster than it is being recharged. Twenty-one of the world’s 37 largest aquifers are beyond their sustainability tipping point. India is the largest groundwater user in the world, relying on it for 60 per cent of its irrigated agriculture. Cheap pumping technology and absence of fees and regulations have encouraged farmers to sink over 21 million tubewells. Some aquifers are now critically over-taxed, and existing wells constantly have to be deepened or replaced. Similarly, in North Africa and the Arabian Peninsula, aquifers created during the last ice age are rapidly being sucked dry. Satellite mapping has shown the Arabian aquifer as the most stressed of all. Many cities in Asia and the Americas rely on groundwater, which is preferred to surface water for drinking because it is less subject to contamination. However, heavy withdrawals lead to saltwater intrusion in coastal areas, turning the water supply brackish and unusable. Exhaustion of aquifers also causes land subsidence. Aquifer recharge is now an important focus of sustainable groundwater management. In some water-scarce rural areas there has been a rediscovery of traditional recharge methods, such as rainwater harvesting, check-dams in stream beds and contour bunds on slopes to contain the run-off from precious downpours.
Q 4 Rising Demand
28
Copyright © Myriad Editions
6 Competition and Conflict R
29
Competition and Conflict
Nile Basin
As populations grow and more water is extracted, competition over the exploitation of rivers, lakes and aquifers increases. Where major water sources cross national boundaries, this can lead to political tension. Many countries share rivers, and some depend heavily on water flowing in from elsewhere. When rivers are dammed or flows diverted in such a way as to benefit one population and deprive another, the potential for conflict increases sharply. The discharge of pollutants can also pit downstream against upstream inhabitants. These pressures have led to talk of “water wars”. So far, no war has been explicitly fought between nations over water, although occasional military, terrorist or activist strikes have been undertaken to destroy dams, cut off supplies or capture sites as part of a populist or other type of campaign. Sabre-rattling over some upstream hydraulic projects has also become increasingly noisy. Water supplies feature strongly in some major political disputes, including that between Israel–Palestine. In Central Asia, confrontation has developed between six republics over what used to be a centralized dam and irrigation network in the days of the Soviet Union. In India, a dry year can lead to inter-state violence over ungenerous water releases by upstream states. Competition between user groups with conflicting interests is not uncommon. Industrial users and farmers may dispute use of scarce resources, or companies with a commercial interest in water supplies may find themselves at loggerheads with local people who rely on the same supply for cultivating their basic crop. Water disputes need to be solved at the basin-wide level, whether this is within one country but between states (as in India); or international, as in the case of the Nile and Indus. An increasing number of tribunals and river basin organizations have come into existence for this purpose.
The Nile is shared by Burundi, DR Congo, Egypt,