A World of Water Woes

(page 3 of 3)

Water use in the U.S.

Household uses of water

World water availability

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In the Southeast, the second-lowest rainfall total on record has collided with increasing populations to create a major drought. In most of the rest of the country, rainfall has been normal or above normal.

The international distribution of water is still more uneven. While the Americas and Europe have relatively abundant fresh water supplies, Africa and Asia have more limited resources (see chart). Rising populations will increase the stress in these regions, while populations in Europe and North America are growing more slowly. By 2025, the availability of water in Africa will approach crisis levels, not just in the immediate sub-Saharan regions, as it is now, but throughout the continent. The problem is aggravated by the lack of adequate water treatment facilities, which can make even the limited water supplies unusable.

How Global Warming Fits In

It seems strange that global warming may actually cause water shortages. After all, if glaciers are melting and sea levels rising, shouldn't that mean more water? But there is a difference between water and usable water. Salt water doesn't help farmers.

Global warming's effect on total rainfall is somewhat ambiguous. Some models suggest that rainfall could slightly rise, while others indicate it will decline (Peter Gleick, "Water: The Potential Consequences of Climate Variability and Change for the Water Resources of the United States," U.S. Global Change Research Project, U.S. Geological Survey, September 2000). However, all show that rainfall patterns will change. This creates a problem because current agricultural arrangements are matched to historical rainfall. If the rains change, the farmers will have to adapt or move.

The timing of the rain may also change. A reduced snow pack will mean less availability of water in the spring and early summer, when farmers need it most. Many models show more monsoon-like conditions in the southern U.S., with heavy rains for part of the year followed by seasonal droughts. This shift will require significant investment in reservoirs, and it will reduce availability at times when crops need rain most.

The problem will be much more critical in tropical countries, where almost all models show higher temperatures and less rain. The shift will further cut incomes in the poorest regions of the world, and in areas where water is already least available. Countries like Australia, which already has a severe deficiency and has been depleting the aquifers at an alarming rate, will have significant additional strain on water resources. (For an interesting discussion of Australian water, see Jared Diamond's Collapse)

Coping with rising populations and the vagaries of rainfall, and dealing with the still-debated effects of climate change will be difficult for those whose job it is to manage the world's stressed water supplies. There are solutions, although many of the proposals seem costly and, in some cases, use so much energy as to be self-defeating for the global economy. The capital required to improve water treatment, so that more of it can be used, to transport water to where it is needed, to change technologies to use less water, and, in extreme cases, to desalinate water, will be a strain on the public infrastructure. The cheapest way to create water is to conserve and reuse it.

Wyss is chief economist for Standard & Poor's in New York .