Groundwater Recharge in the Southern Amargosa Desert Using Surface- Runoff Chemistry-11489

ABSTRACT Accurate estimates of groundwater recharge are necessary components for understanding longterm sustainability of groundwater resources and predictions of groundwater flow rates and flow directions. Amargosa Desert regional groundwater studies show that the surface runoff infiltration occur in the arroyos following runoff producing storms, and this infiltration is considered to be a major source of groundwater recharge. The present study attempts to investigate how water chemistry evolves during the surface runoff and infiltration processes, in the southern Amargosa Desert. In this ongoing study, four surface runoff samplers (SRS) were installed at two different arroyos in the southern Amargosa Desert to capture the surface runoff water. The sampling process included sediment, precipitation, and SRS water samples. In total, four SRS, six sediment, and two precipitation samples were collected between September, 2009 and January, 2010. Analysis of chloride and the stable isotopes of water show substantial overlap of values with underlying groundwater consistent with the concept that infiltration of surface runoff is a major contributor to groundwater recharge in the study area. Groundwater ion concentrations represent a large collection of infiltration events occurring over time, and an exact match with surface runoff samples is unlikely. The SRS design proved its ability to function in arid weather conditions and capture surface-runoff. Further sample collection, statistical analysis, and infiltration modeling will be required to fully describe the evolution of water chemistry between infiltration and old groundwater