The Lower St. Johns Watershed covers an area of 1,378 square miles in northeastern Florida. The hydrology of the watershed is primarily influenced by the St. Johns River, which is the longest river in the state. The watershed receives an average annual rainfall of around 50 inches. The snowpack is not a factor in this region due to its subtropical climate. The surface water of the watershed is used for various purposes including irrigation, drinking water supply, and recreational activities. The constituents of the reservoirs within the watershed include sediment, nutrients, and organic matter. Some interesting climatic facts and trends in the region include the increase in sea level and frequency of extreme weather events due to climate change. The watershed is also susceptible to flooding during major storm events such as hurricanes.