Making every drop of water count

With floods and torrential rains hitting many parts of the world, it is important to remember that the world as a whole faces an increasing shortage of usable water. Increasing the effectiveness with which water is used must become a top priority.

Recent pictures of vast areas of flooded land in Bangladesh and elsewhere, with warnings of worse to come if current patterns of global warming are not reversed, are a vivid reminder of what happens when communities are faced with too much water. At the other extreme, droughts in the Sahel and other parts of sub-Saharan Africa send an equally stark message about what happens when there is not enough water to meet basic human needs (again an increasingly likely occurrence for certain parts of the world).

Both extremes, however, tend to divert attention from the fact that in most parts of the developing world the biggest problem is not so much the overall amount of water available, but what is done with it. In many parts of South Asia, for example, rainfall is abundant at different times during the year, notably during the monsoon period. But without adequate storage and distribution facilities, an excess of supply can, at other times of the year, turn into a shortage that cripples agriculture and holds back social and economic development.

The problem is made even worse by the pressures of growing population. It has been estimated it can take between 2,000 and 5,000 litres of water to produce one person's daily intake of food. This is the amount of water that is transformed by plants into vapour as they grow, a process known as 'evapotranspiration'. The figure dwarves the amount of water used either for drinking or for other household tasks. And it implies that, as a country's population grows, agricultural demand for water can increase dramatically.

The consequences can be severe. Some are long-term; a country that cannot provide adequate food for its population will inevitably be unable to achieve sustained economic growth. Pressure on water supplies can lead to major environmental or health hazards (witness the arsenic poisoning now being experienced in large areas of Bangladesh and surrounding regions as a result of a decision to dig deep wells to replace vanishing ground-water). Wildlife conservation can be critically threatened. And perhaps most acutely, disputes over water supplies have become one of the biggest sources of tension and conflict between neighbouring states, in areas from the Middle East to Latin America.

Minimising wastage

What needs to be done? There is no quick solution. But one central component of any strategy, as a discussion paper drawn up by an international group of scientists pointed out last week, must be to ensure the better use and management of the water that is available. In a 'blue paper' entitled Investing in water for food, ecosystems and livelihoods, researchers at the International Water Management Institute (IWMI) in Sri Lanka called for a major global effort to raise levels of water productivity to ensure that, at least in those areas where adequate rainfall exists, the techniques are in place to ensure that it is not wasted.

A variety of techniques already exist to enable this. The scientists draw attention, for example, to the importance of the concept of rain-harvesting — the use of integrated technologies that seek to ensure that water is captured when it falls as rain, appropriately stored, and finally used in effective ways. They also recommend improved crop varieties capable of using water more efficiently and drought resistant seeds.

Precise micro-irrigation techniques that can avoid excess water use also have a substantial contribution to make. Indeed, according to the prediction of one official from a non-governmental organisation closely involved in small-scale technologies, the design and mass dissemination of a new generation of affordable small-plot irrigation technologies "will have a more dramatic positive impact on the lives of the rural poor than the introduction of personal computers created in the west".

Using a range of such techniques, the scientists argue, could help accommodate the food needs of increasing populations without disrupting ecological systems. Their conclusion is that "business as usual is not an option" — and that while potential solutions exist, "they are not necessarily the ones that have received the most attention".

Alternative strategies

Of course, other approaches to the problem should not be dismissed entirely. One is to encourage the use of alternative sources of water, such as wastewater or seawater. The drawback to wastewater, which is already widely used for irrigation by farmers in the developing world, is that it can pose serious health and environmental risks. The use of seawater may help in coastal areas and where saline-resistant plants have been developed. Where overall water supply is limited, its value is more restricted.

A second approach is to promote an international trade in 'virtual water', with countries lacking water resources importing staple foods from those that that have more than they need. This would certainly have the advantage of freeing up scarce water for higher value uses. But, as the IWMI researchers point out, expecting a trade-based solution to water issues is highly optimistic — look at the difficulties being encountered by climate policies that seek to adopt a similar strategy — while countries that currently lack significant water supplies are already being forced to import food.

Thirdly, some advocate a widespread change of diet, based primarily on the fact that vegetarian diets can, overall, require only about half the total amount of water needed by diets from grain-fed cattle. In principle, this seems a desirable option; in practice, achieving a massive shift of eating habits is an unrealistic goal, particularly in the short-term and while much of the developing world is already suffering from a shortage of calories.

Policy changes are needed

The scientists who compiled last week's report do not deny that each of these alternative strategies can make a contribution to resolving the overall problem. Nevertheless they argue — with considerable justification — that encouraging the more effective use of water supplies, unglamorous as it may be, is likely to provide the most realistic hope of achieving significant progress.

And progress is certainly needed. Two of the Millennium Development Goals, identified by the United Nations and endorsed by all the organisation's member states, are to halve, between 1990 and 2015, both the proportion of people who suffer from hunger and the proportion of people without sustainable access to safe drinking water and basic sanitation. Achieving each of these will require significant effort from all those concerned. And the fact that the water demands of the two often conflict will only make it more difficult.

Finding a satisfactory resolution to this conflict is thus equally urgent. "If we continue to suck our rivers dry, the effects on the environment and people's livelihoods could be calamitous," says David Molden, one of the key authors of the IWMI document, which is intended primarily to open up discussion of the issues, as part of a comprehensive assessment of water management in agriculture initiated by the Consultative Group on International Agricultural Research (CGIAR).

The eventual goal is "to enable farming communities, governments and donors to make better-quality investment and management decisions in the near future, and over the next 25 years". Few would disagree with the importance of this task.
 
Investing in water for food, ecosystems and livelihoods