Identifying Hydrological Inputs to New Wetlands on the Shores of the Retreating Salton Sea, Imperial County, California

The Salton Sea, located in the Salton basin between the Imperial and Coachella valleys, started shrinking in 1999 when surrounding farms shifted to more efficient agriculture and transferred irrigation water to large coastal cities for short-term use. Since then, the shrinking lake has become a hazard to surrounding towns as it contains toxins from the agricultural irrigation runoff that once sustained the lake. Wetlands have emerged near Bombay Beach's town on the northeast shores of the retreating Salton Sea. This study aims to identify water sources contributing to the wetlands. Understanding water sources and quality is vital in sustaining the wetland's biodiversity. This wetland is unique because, unlike the other wetlands in the area, agricultural irrigation runoff is not a contributing water source. On the north shore, lining of the Coachella Canal in 2006 is responsible for depleting a significant input of canal seepage of Colorado River project water. Other terrestrial water inputs along the north shore are not especially common, except for temporary winter and local monsoonal rains. At Bombay Beach, the main perennial source of terrestrial water comes from a thermal artesian aquifer that supplies water to recreational spas and a fish farm through artesian wells. Waste flows from the thermal spas and fish farm provide input to several local channels that drain into the new wetlands, providing a constant perennial source of water. Water isotopes tested in the thermal artesian water and in the wetlands indicate wetlands are supplied primarily from the locally derived thermal artesian source (averaging -71 del D and -8.7 del O18) with no evidence of mixing with imported Colorado River water. Salinity of groundwater issuing from these artesian wells is in the 4300 to 5200 mg/L TDS range. The thermal groundwater is old, with no tritium detected and carbon-14 near 3.5 pmc.