The Santa Clara River Lakes, located along the San Andreas fault 19 miles northwest of Palmdale, California, were placed on the state’s “303(d) List” or “Impaired Water List” in 1996 for eutrophic conditions, high pH, and low dissolved oxygen. In 2016, the state adopted a Total Maximum Daily Load (TMDL) for nutrients (nitrogen and phosphorus) in the Santa Clara River Lakes. This study focuses on the largest of the three lakes, Lake Elizabeth, which is surrounded by the unincorporated town of Elizabeth Lake, CA. The local community uses on-site wastewater treatment systems instead of a centralized sewer system, resulting in potential contamination of groundwater. In response to concerns over the quality of water in the area and fluctuating water levels in Elizabeth Lake, the U.S. Geological Survey (USGS) cooperated with the Los Angeles Regional Water Quality Control Board to assess hydrologic conditions and water quality near Elizabeth Lake. As part of this work, the USGS did electrical resistivity tomography (ERT) survey lines at two locations across the southern edge of the lake near the community in March 2019.