San Luis Valley: Aquifer levels are moving in the wrong direction #codrought


From The Pueblo Chieftain (Matt Hildner):

The shallow groundwater aquifer leaned on heavily by farmers in the north­central part of the San Luis Valley continued its drought-driven slide in 2012. Allen Davey, engineer for the Rio Grande Water Conservation District, released calculations showing the aquifer declined by 123,000 acrefeet from 2011. Since the district began monitoring the section of the aquifer in 1976, its volume has dropped by 1.2 million acre­feet.

The drop comes despite the fallowing of nearly 30,000 acres and a roughly 20 percent decline in groundwater pumping from wells in Subdistrict No. 1. Subdistrict No. 1, which includes roughly 3,400 irrigation wells in the north­central valley, assesses fees on its members to take farm ground out of production and reduce pressure on the aquifer also while providing mitigation to other water users who are harmed by the pumping.

Steve Vandiver, the district’s manager, pointed to a sustained history of poor flows on the Rio Grande as the cause of the decline. “The problem as I see it is the recovery rate, whether we’re pumping or not, is dependent on what the river runs,” he said. “If we’re in sustained drought, we’re going to have little or no diversions and little or no recovery.” The main source of recharge for the shallow, or unconfined, aquifer comes in the spring when ditches divert from the Rio Grande and deposit that water on farmers’ fields where it waters crops, then filters down. Once the river’s flows dwindle in summer, many valley farmers then turn on their groundwater pumps to pull water from the aquifer and finish their crops through the remainder of the growing season.

“If we don’t have runoff to support this system we have to do more and more to get this turned around,” Vandiver said. He said the subdistrict would have more money to pay for fallowing in 2013.

Travis Smith, who represents the valley on the Colorado Water Conservation Board, said expanded regulation of pumping through the rest of the valley was needed to help recover the aquifer.

More Rio Grande Basin coverage here.

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