Ram Fishman at George Washington University, US, and colleagues have investigated irrigation in India because of increasing groundwater shortages. Dams in the country are often near-empty, says Fishman, while people are forced to dig deeper wells to chase the remaining groundwater. "Water tables are falling all around India, as farmers pump out more water than is naturally replenished," he added.

The researchers combined data on farming areas and irrigation in India with detailed climate data, entering it into a computer simulation to calculate what would happen to water resources under different behavioural scenarios.

Currently most farmers irrigate by flooding &nash; a highly inefficient method, since it allows a large proportion of water to evaporate. Fishman and colleagues looked at the potential benefits of more efficient irrigation technologies. These included sprinkler and drip irrigation, in which water is delivered directly to crop roots, and crop varieties that manage with less water.

The researchers found that although technologies like drip irrigation could slash excessive groundwater consumption by two-thirds, in a "realistic" scenario half of this reduction would be lost as farmers expanded their horizons.

"If farmers use a technology that requires less water per acre, they might still like to use the same total amount of water to irrigate a greater area, rather than keep the water in the ground," said Fishman. "Especially if they don’t pay any cost per unit of water they use."

Like many developing countries, India seldom regulates or charges for use of its groundwater. Meanwhile, the electricity used for pumping is heavily subsidized and, when priced at all, priced at a flat rate.

Groundwater irrigation is believed to support about half of the country’s population, and generate 70% of production. Fishman and colleagues believe there should be economic incentives for water conservation. As an example, Fishman suggests charging per unit for the electricity used to pump groundwater.

"Technology can save a lot of water, but adoption [of it] by itself my not lead to water saving, without proper economic incentives for conservation," he said.

Fishman and colleagues reported their findings in Environmental Research Letters (ERL).

Related links

Related stories