The study, co-authored by NMSU water resource economist Frank Ward and Manuel Pulido-Velazquez of Spain and published in the Proceedings of the National Academy of Sciences, looks at the big picture of water conservation — how much is removed from an entire river basin as opposed to how much comes out of a single faucet. Specifically, the authors focus on whether subsidizing drip irrigation would improve basin-wide conservation, and they say it would not.

As The Los Angeles Times notes today, “It’s the opposite of conventional wisdom.” The study conducted on the upper Rio Grande found that drip irrigation provides more water to each plant, but that increases crop yields and therefore loses more water to evapotranspiration. A key finding is that the centuries-old method of flood irrigation initially uses more water, but that the excess flows back into the aquifer and can be used by another farmer downstream.

In their abstract, the authors conclude:

Adoption of more efficient irrigation technologies reduces valuable return flows and limits aquifer recharge. Policies aimed at reducing water applications can actually increase water depletions. Achieving real water savings requires designing institutional, technical, and accounting measures that accurately track and economically reward reduced water depletions. Conservation programs that target reduced water diversions or applications provide no guarantee of saving water.

Ward told the Independent that he expects his study will raise some eyebrows around a state where water conservation is seen by many as the holy grail and where flood irrigation is often seen as wasteful and inefficient.

“It could have an effect on how water is administered and how water is subsidized,” he said. “Paying for (drip irrigation) subsidies would make farmers better off and increase food production” at one farm or area, but the study suggests it would reduce the amount of water available to farmers downstream, Ward said. “Then it becomes a political decision.”