WASHINGTON — In 2009, the most recent year for which global data are available from the United Nations Food and Agriculture Organization, 768 million acres in the world was equipped for irrigation but only 84 percent of that area was actually being irrigated, according to new research conducted by the Worldwatch Institute for its Vital Signs Online service (www.worldwatch.org).
As of 2010, the countries with the largest irrigated areas were India (96 million acres), China (46 million), and the United States (42 million), according to report author Judith Renner.
The irrigation sector claims about 70 percent of the freshwater withdrawals worldwide. Irrigation can offer crop yields that are two to four times greater than is possible with rainfed farming, and it currently provides 40 percent of the world’s food from about 20 percent of all agricultural land.
Since the late 1970s, irrigation expansion has experienced a marked slowdown. The FAO attributes the decline in investment to the unsatisfactory performances of formal large canal systems, corruption in the construction process, and acknowledgement of the environmental impact of irrigation projects.
The increasing availability of inexpensive individual pumps and well construction methods has led to a shift from public to private investment in irrigation, and from larger to smaller-scale systems.
The takeoff in individual groundwater irrigation has been concentrated in India, China and much of Southeast Asia. The idea of affordable and effective irrigation is attractive to poor farmers worldwide, with rewards of higher outputs and incomes, and better diets.
But if groundwater resources are overexploited, aquifers will be unable to recharge fast enough to keep pace with water withdrawals. Not all aquifers, however, are being pumped at unsustainable levels — in fact, 80 percent of aquifers worldwide could handle additional water withdrawals.
With predictions of a global population exceeding 9 billion by 2050, demand for higher agricultural output will put more strain on water reserves. Even without the effects of climate change, water withdrawals for irrigation will need to rise by 11 percent in the next three decades to meet crop production demands.
Source: Worldwatch Institute.