The San Francisco Coastal South Watershed (HUC 18050006) spans an area of approximately 317 square miles in California. The watershed is characterized by a Mediterranean climate with cool, wet winters and dry summers. Precipitation in the form of rain and snow is the primary source of water for the watershed. The snowpack in the Sierra Nevada mountains contributes significantly to the water supply, especially during dry seasons. The watershed contains several small reservoirs that are used for water storage and supply. The reservoirs are mainly composed of sediment and organic matter. Interesting climatic facts include the high variability in precipitation and temperature, which can lead to droughts and flooding events. Recent trends show an increase in temperature and a decrease in precipitation, which could have significant impacts on water resources in the watershed.