Washington, Nov 28 : A new study has suggested that modern drip irrigation, also known as micro-irrigation, may lead to the depletion of underground water.
Invented by an Israeli water engineer, micro-irrigation runs water through plastic tubes that release the flow through small holes directly to crop roots or stems.
The precise application allows drip-irrigated crops to be watered more frequently than with traditional sprinkler methods. As a result, many governments have encouraged drip irrigation as a water-conserving technology that can boost crop yields.
But, according to a report in ENN (Environmental News Network), drip irrigation may have a downside.
In traditional flood or sprinkler irrigation, "wasted" water, which is the water not absorbed by crops, seeps into the ground and recharges the below-surface aquifers used by area farmers.
As drip irrigation becomes more common, recharge of groundwater may be less frequent, according to the study.
"I think it's very true that drip irrigation and drip irrigation subsidies definitely contribute to food security and increased farm income," said Frank Ward, the study's co-author and a professor of water resource economics at New Mexico State University.
"The only downside is that drip irrigation could be using more water," he added.
If Ward's study is true for areas beyond the study's focus area - the U.S. Rio Grande Basin - agricultural development organizations may need to evaluate whether costly drip irrigation is truly an efficient technique.
Ward first became aware of drip irrigation's potential to diminish water reserves when several irrigation engineers, farming consultants, and water agency administrators in the Rio Grande Basin informed him of the problem.
They told Ward that farmers who adopted the technology were using a larger portion of the region's groundwater.
After initially dismissing the concerns, Ward and Spanish researcher Manuel Pulido-Velazquez created a model of the basin's hydrology, which included the total water diverted from streams, applied to crops, evaporated into the air, and returned to the ground.
At maximum levels of drip irrigation subsidies, the analysis concluded that farmers in the irrigation district would apply 40,000 acre-feet less of water per year.
Yet due to the loss of "wasted water" and the additional water demands associated with the higher yields of drip irrigation, the entire district would face a deficit of 36,700 acre-feet of water per year.
"Farmers themselves believe they are using less water," Ward said. "They apply less, but because plants unknowingly may use more, they deplete more," he added.
This is of particular concern as global food crises and water shortages force many regions to decide between growing food or conserving water.