August 22, 2016-- Warmer world may not impact Upper Colorado groundwater (Grand Junction Sentinel)

A new U.S. Geological Survey finds groundwater levels in the Upper Colorado River Basin may hold steady over the rest of this century despite a warming climate. The revelation comes just months after another study by the same agency found that groundwater accounts for 56 percent of streamflow in the Upper Colorado basin. The studies offer some hope of groundwater helping mitigate other water-related impacts of a changing climate in coming decades. Perhaps most importantly, groundwater could help maintain later-season streamflows at a time when snowpack runoff is expected to occur earlier in the year, resulting in additional strains on water supplies and reservoir storage during the summer months. The climate-change study is published in the journal Geophysical Research Letters. It finds that increased precipitation predicted by climate-change models should be enough to offset the impacts of warmer temperatures on groundwater levels in the basin.

Fred Tillman, a USGS scientist and the report’s lead author, said researchers considered how groundwater outputs and inputs would be affected by climate change. Earlier snowmelt as temperatures warm will mean native vegetation greens up and begins using water through a process called transpiration earlier each year. This and more evaporation of water from soils and water bodies will increase water loss from the basin. “We knew that we had more going out from the higher temperatures. What we found was, well, we actually had more precipitation coming in too, according to these (climate-change) models,” Tillman said. Researchers view the base flow of streams as a proxy for the groundwater discharge into them, apart from surface flows from snowmelt and rain. Eric Kuhn, general manager of the Colorado River District in Glenwood Springs, said one thing water managers have been concerned about is that future late-summer base streamflows will be extremely low as the climate changes. He said he hasn’t yet read the new study, but it may be that groundwater levels will hold up better than expected due to higher precipitation. “Perhaps the late-season, low-flow period will not be as bad as we once thought it would be,” he said. “With a little more groundwater it offers a little more help” late in the season, Kuhn said. To view the full article visit the Grand Junction Sentinel.