The Salton Sea is the largest lake in California and is an endorheic, shallow, hypersaline lake. The surface water elevation of the Sea is currently 238 feet below sea level, and has been maintained by agricultural return flows from Imperial Valley farming, and two rivers- the New River and Alamo River- which originate in Mexicali, Mexico. The current salinity is at 74 ppt and is expected to increase due to the Quantification Settlement Agreement that was signed in 2003, stipulating the transfer of 500,000 acre-ft of Colorado River water to urban areas until 2075. This results in less flow to the Salton Sea and the declining water level has exposed 220 square miles of dried up playa, creating dust storms that have become the highest risk factor for asthma and cardiovascular diseases to the population around the Sea. Massive fish and bird kills began in the 1980s and continue to occur periodically. The Sea that was once the main Pacific flyway is now named as “IBA in Danger” by BirdLife International.
In this study, the Delft3D numerical modeling suite- FLOW, WAVE and WAQ- was utilized to investigate transport and cycling of nutrients under the influence of wind-induced sediment resuspension activity. The three-dimensional hydrodynamic and water quality combined model was applied to simulate mitigation scenarios to assess long-term effects on salinity and water quality of 1) emerged islands, 2) seawater import/export, and 3) seawater import/export in addition to treating tributary rivers to remove nutrients treatment.
Overall, this study supports the findings from previous studies and showed that sediment resuspension is an important factor that influences orthophosphate concentration in the water column, and that emerged islands have long term potential on enhancing burial activity for pollutants removal in the Salton Sea. Furthermore, the seawater import/export mitigation scenario showed promising results of reducing salinity level from 46 ppt to 38-39 ppt in two years. The three-dimensional hydrodynamic/water quality model developed in this work is the latest numerical model tailored to the Salton Sea’s system, and has the potential to improve understanding of biogeochemical processes of chemical substances that lead to detrimental effects, and facilitate future restoration plans for the Salton Sea.