Environmental Isotopes Delineate Recharge Sources in the Coachella Valley Aquifer, California
Wednesday, December 5, 2018: 11:40 a.m.
Exhibit Hall- C4 & C5 (Las Vegas Convention Center)
Groundwater in the Coachella Valley is a critical resource satisfying water demands in Palm Springs, other nearby communities, and farms. To support sustainability planning, this study was conducted to determine areas and sources of groundwater recharge in the Coachella Valley Aquifer. Field data collection included water sampling for stable water isotopes and major ions at feeder tributaries and water wells in subbasins in the Coachella Valley Aquifer, and integration of published radioisotope and stable isotope data collected by water purveyors, USGS and other entities. Springs and surface flows were also collected at different elevations in the San Bernardino and San Jacinto Mountains at tributary streams that feed into the Coachella Valley Aquifer. Data indicate variable stable water isotope signatures related to origin and source of recharge water, suggesting that subbasins are recharged by precipitation falling closer to valley floors and peripheral mountain fronts, rather than from runoff of rainfall and snowmelt from high elevations in the San Bernardino and San Jacinto Mountains. Carbon-14 and tritium data reinforce these interpretations. In addition, recharge in different subbasins in the Coachella Valley Aquifer suggest unique tributary inputs in the upper parts of the subbasins, along with water mixing due to groundwater underflow between subbasins. Recharge by water imported from the Colorado River was also detected, but is limited to areas near recharge basins in the western part of the Coachella Valley Aquifer where recharge basins have existed for decades.