A new paper in JGR-Atmospheres raises some significant questions about snowmelt and groundwater in the western U.S. in a CO2-warmed world. Sam Earman of the Desert Research Institute and colleagues used isotopic analysis to try to tease out the relationship between snowmelt and groundwater recharge. They found that, while 25 to 50 percent of precipitation falls as snow, snow is responsible for 40 to 70 percent of groundwater recharge at their study sites. Given the clear evidence of declining snowpacks in the west (see here), the implications are significant:

On the basis of these results and presently accepted scenarios for alterations in precipitation in the western United States over the next 50 years (significantly decreased snowpack due to increased atmospheric CO2), investigations of how climate change may affect groundwater resources are needed.

No answers here, just interesting questions.