In many countries, water scarcity represents a critical constraint to food production and a major cause of poverty and hunger. Improved water management is one of the keys to producing enough food to alleviate the suffering of today and feed an additional 3 000 million people by the year 2030.
WATER RESOURCES, until recently considered cheap and plentiful, are now recognized to be scarce and valuable. More than 230 million people live in 26 countries classified as "water deficient", 11 of which are in Africa. And the number of countries facing severe water shortages is likely to increase dramatically in the next decade.
By the year 2000, six out of seven East African countries and all five North African countries bordering the Mediterranean will face acute water shortages. All the countries in North Africa, except Morocco, already import half or more of their grain.
Demand for water is escalating, contributing to intensified competition among users. In many areas, giving water to one user means denying it to another. In a world where available surface fresh-water resources are extremely unevenly distributed, this has the potential to provoke national, regional and international disputes.
Water availability per caput
WITHOUT investments in water, the prospects for improving food production and increasing food security are remote.
Agriculture accounts for over two-thirds of the world's water withdrawal, yet in the future this share is likely to come under increasing pressure from other sectors with greater purchasing power. In many areas, water scarcity already severely limits food production and threatens food security.
Pressure on agricultural land is contributing to the expansion of rainfed agriculture into marginal areas characterized by risky rainfall regimes. This is forcing millions of impoverished people to undertake unsustainable farming systems in ecologically fragile areas.
To partly offset the variability of rainfall, farmers tend to select crops with the genetic capacity to withstand the risks of rainfall failure. Many poor farmers are reluctant to grow high-yielding varieties that require large amounts of water, since one crop failure can threaten the survival of their entire household.
Estimated annual world water use:
Irrigated area by region, 1990
Irrigated land is more than twice as productive as rainfed cropland. Today, only 16 percent of the world's croplands are irrigated, but those lands yield some 36 percent of the global harvest.
In the developing countries, irrigation increases yields for most crops by 100 to 400 percent. Irrigation also allows farmers to reap the economic benefits of growing higher-value cash crops.
Half or even two-thirds of future gains in crop production are expected to come from irrigated land.
In the developing world, where about 20 percent of arable land is irrigated, the prevalence of irrigation varies widely within and among countries and crops. Irrigation makes the greatest contribution to global food security in Asia. Irrigated lands account for as much as 80 percent of food production in Pakistan, some 70 percent in China and over 50 percent in India and Indonesia.
In Africa, where only about 10 percent of food production comes from irrigated lands, FAO calculates that irrigation has been developed on only 30 percent of 42.5 million hectares with irrigation potential.
A World Bank/UNDP study estimates that irrigation could be extended over an additional 110 million ha in developing countries, producing enough more grain to feed 1 500 to 2 000 million people.
POORLY managed l irrigation contributes l to water shortages and _ pollution, land degradation and the spread of waterborne diseases.
In many regions, water is being pumped out of the ground for irrigation faster than it can be replenished. Overpumping in India's Tamil Nadu state has lowered the water table by 25 to 30 m in a decade. Much of this water is wasted. As much as 60 percent of the water withdrawn for irrigation often does not reach the crop. It is lost through canal leakage, spillage, infiltration and unproductive evaporation, although some of this water reaches the river or groundwater, allowing it to be used by others downstream.
Poor drainage and irrigation practices lead to waterlogging and salinization, which have sapped the productivity of nearly 50 percent of the world's irrigated lands.
Unless irrigated fields are drained properly, salt builds up in the soil as water! evaporates, making the land infertile. Salinity now affects more than 20 percent of the irrigated land in China and Pakistan.
Irrigation losses: where the water goes
LARGE-SCALE irrigation projects are beyond the reach of many poor farmers, but a variety of small-scale, affordable techniques can increase food production. Examples include: Water harvesting. Collecting runoff and using it to irrigate crops, pastures and trees can significantly improve both yields and the reliability of agricultural production. Experience in Burkina Faso, the Sudan and Kenya shows that rain harvested from one hectare for supplementary irrigation of another can triple or even quadruple production.
Low-lift pumps. Cheap, pumps, along with increasing availability of fuel, have revolutionized irrigation. Small pump schemes, individual and communal, have begun to play an important role in augmenting food production. Pump schemes are easy to install and simple to operate. They also provide indirect benefits by linking water for domestic use to irrigation.
Treadle pumps. Simple, inexpensive walking pumps have enabled poor farmers in many Asian countries to increase their incomes and production by allowing a second crop to be harvested during the dry season, new varieties of vegetables to be planted and crops to be grown in semi-arid areas. These pumps are often operated by women, who also use them to obtain drinking-water.
Water management potential in Africa
(area in millions of heatares)
FAO recently estimated the potential for using water in agriculture on the basis of soil, climate and water conditions. The results confirmed that irrigation is far from being the only source of agricultural water control in Africa. A huge untapped potential remains available for water harvesting and agricultural management of lowland and valley bottoms.
IMPROVED water management holds the key to increasing food production through use of high-yielding varieties and improved cultural practices. Global targets by the year 2010 are:
Key steps toward achieving these goals include:
For further information, please contact:
Food and Agriculture Organization of the United Nations
Viale delle Terme di Caracalla, 00100, Rome, Italy
Information Division, Tel: (39-6) 5225-3276/5225-4781/5225-4243
Plant Production and Protection Division, Tel: (39-6) 5225-4986
Internet, http://www.fao.org or gopher.fao.org