Assessing Fish Habitat and the Effects of an Emergency Drought Barrier on Estuarine Turbidity Using Satellite Remote Sensing

Estuaries worldwide are experiencing stress due to increased droughts, which often prompt intervention by environmental managers and government agencies. Effective management of water resources in estuarine systems can be enhanced by new technologies and methodologies to support decision‐making processes. Here, we evaluate the use of high‐frequency, high‐resolution satellite remote sensing within two management‐relevant case studies in the San Francisco Estuary and the Sacramento–San Joaquin River Delta. We used a remote sensing‐derived time series of turbidity maps to (1) identify favorable turbidity conditions for the endangered fish species, delta smelt ( Hypomesus transpacificus ), during the height of the great California drought in the dry season of 2015, and (2) evaluate changes in turbidity following the installation of an emergency saltwater intrusion barrier. The mapping results indicate several persistent areas of turbidity refugia throughout the summer in the north and west Delta; however, there was infrequent connectivity. A comparison of images captured during ebb tides before and after barrier installation showed a mean increase of 6.6 Nephelometric Turbidity Units (NTU) in the San Joaquin River and 4 NTU in Fisherman’s Cut. Our assessment of the barrier supports previous findings, which used field samples to conclude barrier installation may have resulted in increased turbidity near the barrier and enhances these findings by providing spatial context.