The Middle San Joaquin Lower Watershed (HUC 18040001) is located in the central valley of California and covers approximately 5,663 square miles. The watershed is fed by the Sierra Nevada snowpack and experiences a Mediterranean climate with hot, dry summers and mild, wet winters. The snowpack typically peaks in April and May, providing a significant source of surface water for the region. Agriculture is the dominant land use, and irrigation is necessary due to the semi-arid climate. The surface water in the watershed is primarily stored in several large reservoirs, including Millerton, Pine Flat, and Eastman, which are used for both irrigation and recreation purposes. The reservoirs' constituents include sediment, nutrients, and harmful algal blooms. Interesting climatic facts include the high variability in precipitation and the increase in temperature and frequency of extreme weather events over the past several decades.