Higher streamflow, groundwater Subdistrict No. 1 curtailments, boost unconfined aquifer by 71,440 acre-feet in 2014

Blanca Wetlands via the National Park Service
Blanca Wetlands via the National Park Service

From The Pueblo Chieftain (Matt Hildner):

Irrigators and water officials looking to conserve groundwater in the San Luis Valley got a small dose of good news this week. The volume in the unconfined aquifer — the shallower of the valley’s two major groundwater bodies — increased by 71,440 acre-feet in 2014.

“We did turn the corner,” said Allen Davey, an engineer who conducts the Rio Grande Water Conservation District’s groundwater monitoring.

The increase was the first since 2009.

Davey attributed the hike to better stream flows than had been seen in recent years.

He also pointed to a decline in pumping in Subdistrict No. 1, which has used a combination of fees on pumping and the fallowing of farm ground to reduce demand on the aquifer in the north-central part of the valley.

The unconfined aquifer has traditionally been used by farmers in the valley to water crops like potatoes, barley and alfalfa when the availability of surface water declines in mid- to late-summer.

Recharge to the shallow aquifer occurs from streams entering the San Luis Valley floor, canal leakage and irrigation return flows.

Despite this year’s slight improvement, the unconfined aquifer has declined by more than 1.2 million acre-feet since monitoring began in 1976.

An acre-foot is the equivalent of roughly 325,000 gallons of water.

The long-term decline is of concern to the managers of Subdistrict No. 1, who have the goal of increasing the volume of the unconfined aquifer by 800,000 to 1 million acre-feet.

David Robbins is an attorney for the Rio Grande district, which acts as the umbrella organization for the subdistrict.

He said the subdistrict’s board is wrestling with the question of whether to seek a change in its water management plan.

“There are many within the subdistrict boundaries and elsewhere who are concerned there hasn’t been a more dramatic increase in water supply within the subdistrict,” he said.

More San Luis Valley groundwater coverage here and here.

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