the prospect of water shortage. Water use grew at more than twice the rate of population increase in the last century. On current trends, by 2030 global freshwater withdrawals will exceed prospective reliable supplies by 40 per cent, with the disparity in some places being more than 50 per cent. At the same time, in some settings, water infrastructure and river diversion to fill reservoirs, irrigate crops and support industrialized lifestyles have already manipulated natural watercourses to the limits of possibility. An increasing number of important rivers – including the Colorado (USA and Mexico), the Indus (India and Pakistan), the Huang He (China), the Rio Grande (North America and Mexico), and the Murray (Australia) – run dry, or almost do so, before they reach the sea for large parts of the year. Groundwater is also being pumped at rates that deplete aquifers and normal underground recharge into rivers and lakes. Erratic weather patterns associated with climate change, in the form of multi-year droughts or altered monsoon behaviours, are also increasing the prospects of water shortage in vulnerable areas.
Q 2 Water’s Unequal Distribution
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Water stress in countries supplied from Himalayan sources
Population growth, economic expansion and rising living standards are exerting ever more pressure on supplies. In India, freshwater availability per capita has declined from over 4,000 cubic metres to 1,500 cubic metres in less than 50 years. In major river basins shared by Afghanistan, China, India and Pakistan there is strong competition between farmers, industrialists, and urban consumers and the potential for conflict. The depletion of water resources, when combined with annual and seasonal rainfall variability and vulnerability to drought and/or flood, creates severe water stress.
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4 Rising Demand; 5 Dwindling Supply; 6 Competition and Conflict R
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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More than 4,000 cubic kilometres of fresh water are withdrawn every year – equivalent to roughly 1,700 litres per person per day.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
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HOW WATER IS USED
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5 Dwindling Supply; 6 Competition and Conflict R
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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
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