San Luis Valley: Fallowing of acreage irrigated by pumping to start this season, reduction of 5,000 acre-feet is the target

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The Rio Grande Water Conservation District has been working diligently for several years to set up groundwater subdistricts to reduce pumping from the aquifer underlying the valley. The hope was to avoid having the State Engineer’s office come in a shut down wells as has happened in the South Platte and Republican River basins. The effort in the Valley has led to the creation of groundwater Subdistrict No. 1 which will start operations this season with a goal (set by the State Engineer’s office) of a 5,000 acre-foot reduction. Here’s a report from Matt Hildner writing for The Pueblo Chieftain Click through and read the whole article. Here’s an excerpt:

The unconfined aquifer, or shallower of the valley’s two major groundwater bodies, is recharged every spring when irrigation canals pull water from the Rio Grande River to fields in the district where it percolates down. Farmers pump it back up later in the growing season. But drought and largely unregulated use have seen the aquifer drop by 740,000 acre-feet, down to its lowest level since water managers began monitoring it in 1976. The subdistrict aims to reverse that trend by retiring up to 40,000 acres of farm ground over the next decade, a move they hope would return between 340,000 and 540,000 acre feet to the aquifer.

While the subdistrict doesn’t expect to finalize all of ifs fallowing contracts until April 1, up to 10,000 acres could be pulled from production this growing season, said Steve Vandiver, manager of the subdistrict’s parent organization, the Rio Grande Water Conservation District. “That will probably be 20,000 acre feet we’re not pumping,” he said. “That’s a big start.”[…]

The subdistrict’s other main task will be to replace the injury pumping of wells causes to surface water users. The valley’s aquifers and streams are connected to varying degrees depending on where one is in the area. And for more than four decades the valley’s surface users have had to bear the burden of the state’s compliance with the Rio Grande Compact as irrigation ditches were curtailed so water could be sent downstream. Groundwater wells faced no such burden. But that will change this season. State computer modeling has determined that the subdistrict will have to return 5,000 acre-feet to the river to make up for the injuries caused to surface water owners. While the subdistrict will have to formally submit its replacement plan to the Office of the State Engineer next month, Vandiver said the subdistrict could have between 6,500 acre-feet and 7,000 acre-feet at its disposal. Most of that water is stored in reservoirs on the Rio Grande upstream of the subdistrict.

More San Luis Valley groundwater coverage here and here.

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