Hydrogeologic and hydrochemical inputs to emerging wetlands on the shores of the receding Salton Sea, California

Abstract

The Salton Sea has experienced significant recession over the past two decades due to changes in the diversion of Colorado River water to the Salton Trough for agricultural irrigation. As a result, wetlands have emerged in some exposed playa areas along the Salton Sea, primarily in regions with extensive agricultural return flows and agricultural drainage. One notable wetland system, known as the Bombay Beach Wetlands, has formed on the north shore of the Salton Sea, in an area devoid of agriculture. In many other areas with limited or no agriculture, wetlands have failed to develop, leaving exposed playa surfaces as the Salton Sea recedes. These dry playa surfaces pose a significant threat to the health of local residents due to the presence of toxins contained in windblown dust associated with playa deposits. In this study, stable water isotope data, combined with other hydrological information, led to identification of two potential water sources for the Bombay Beach Wetlands. The first possibility proposes that thermal artesian waters alone contribute to the wetlands' water source, while the second hypothesis involves a combination of drainage from Salton Sea bank storage water mixing with the thermal artesian water. The thermal artesian water discharges into drainage channels that flow towards the Bombay Beach Wetlands, initially devoid of possible groundwater baseflow until reaching the wetlands. Studies were subsequently done along the full reach of the drainage channels receiving thermal artesian water. Dissolved solids content, P and N nutrients, arsenic, and stable water isotopes were tested synoptically along the drainage channels. Channel investigations led to the development of a novel model of salinization, which is linked to channel discharge, channel morphometrics, and channel incision.