Water Scarcities, Irrigation Setbacks Threaten Food Supplies

Worsening shortages of fresh water along with rising costs of irrigation are placing global food supplies in jeopardy, according to a new study from the Worldwatch Institute, a research organization in Washington, D.C.

"As world population grew by more than 3 billion over the course of this century, the spread of irrigation became vital to meeting food needs," said Sandra Postel, the Institute's Vice President and author of the report. "But now, crop shortages may follow on the heels of water scarcities that are rapidly emerging in many regions."

According to Water for Agriculture: Facing the Limits, irrigated area expanded nearly fivefold over this century. One-third of the global harvest now comes from the one-sixth of the world's cropland that is irrigated.

But rising costs for new water supplies, declining irrigation investments, and worsening environmental damage have dramatically slowed that expansion. As a result, world irrigated area is growing slower than population. Per capita irrigated area peaked in 1978 at .48 hectares per person. Since then, it has fallen 6 percent.

"During the nineties, irrigation will likely spread by no more than I
percent annually, while population grows nearly twice as fast," Postel said.

Moreover, irrigation's worsening ecological toll will force some existing land out of production. Poor water management leading to a steady accumulation of salt in the soil has damaged 60 million hectares, roughly onefourth of the world's irrigated land. Now suffering reduced yields, this land requires costly reclamation; some of it will eventually have to be abandoned.

"Overpumping of underground aquifers is causing water tables to fall precipitously in parts of northern China, India, the western United States, and elsewhere. One-fifth of U.S. irrigated land is watered by pumping in excess of recharge, a practice that eventually makes irrigation too costly to continue and can even drain some aquifers dry. Irrigated area in Texas, where groundwater depletion has been particularly severe, has fallen 30 percent from its peak in 1974."

In the Soviet Union, excessive water diversions for irrigation have led to a dramatic shrinkage of the inland Aral Sea. Since 1960, the sea's volume has dropped by two-thirds and salinity levels have tripled. All native fish species have disappeared, devastating the region's fishing industry.

Most unsettling is that water demands in many parts of the world are fast approaching the limits of resources, Postel said. Several areas could enter a period of chronic shortages during the nineties, including northern China, virtually all of North Africa, pockets of India, much of the Middle East, and parts of the western United States.

"Where scarcities loom, cities and farms are beginning to compete for available water. When supplies tighten, farms usually lose out."

In the western United States, supplies are being siphoned away
from agriculture by thirsty cities willing to pay a premium to secure water
for 3 future growth. Tucson, Phoenix, and other Arizona cities have purchased water rights from more than 232,000 hectares of farmland. In Pima County, where Tucson is located, irrigation is expected to disappear entirely by 2020.

Climate change from the buildup of greenhouse gases in the atmosphere further clouds agriculture's water future. Adjusting irrigation systems to altered rainfall patterns will take time and huge sums of money--potentially on the order of $150-300 billion worldwide. It seems inevitable that as global warming progresses, irrigation will be poorly matched to redistributed water supplies for several decades, further threatening crop production.

"Preventing water scarcity from undermining food security will not be easy," Postel said. "It will take vast improvements in irrigation efficiency, widespread investments in smaller and less ecologically damaging projects, and increased productivity on rainfed lands."

A top priority is to reduce water subsidies, which discourage farmers from conserving. In most of the Third World, government revenues from irrigation average only 10-20 percent of the full cost of delivery. Farmers benefiting from the huge Central Valley Project in California have repaid only 5 percent of that project's cost over the last 40 years.

"In the United States, hundreds of federal irrigation contracts will be coming up for renewal during the nineties," Postel said. "If officials seize this opportunity to establish contracts that foster efficiency instead of discouraging it, water stresses in the American West could ease measurably."

As large water projects become harder to justify and fund, investments in a wide variety of small-scale techniques can help boost food production and incomes at the village level.

For example, in India a combination of earthen check dams, small reservoirs to store rainfall, percolation tanks to recharge groundwater, and other simple measures forms a workable and less costly alternative to the huge Sardar Sarovar Dam, which will flood 40,000 hectares and displace 100,000 villagers.

"With the world projected to add some 96 million people per year during the nineties, efforts to improve water productivity can only be stopgaps," Postel said. "The imbalance between human demands and local water supplies will worsen without major efforts to slow population growth and eliminate wasteful practices.

"In a country such as Egypt, where the population leaps by I million every 8 months, modernizing irrigation systems is simply not enough. And in the western United States, using scarce water to irrigate hay for cattle may not be possible for much longer.

"Over time, spreading water scarcity will lead to food shortages and rising food prices. These and other consequences of overstepping water's limits are inescapable; for much of the world, time to avert them is rapidly running out."

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