The Myakka, Peace and Caloosahatchee rivers are the primary tributaries flowing into the estuary. Additional freshwater inflow comes from the Floridian and Hawthorne aquifers.
Barrier islands separate the estuary from the Gulf of Mexico.
Several significant passes between the islands provide access between the open waters of the Gulf and the waters of the estuary. Demographics Inhabited since pre-Columbian times, the Charlotte Harbor watershed remained a sparsely populated agricultural area until the 1980s when major residential growth began. Citrus farming remains the primary agricultural use of the area, but urbanization is replacing farming areas. In recent years, highway and airport construction have made the area far more accessible and is largely responsible for the tremendous population growth that is expected to result in more than doubling the 1980 population of 407,000 to 847,000 by 2020. This continued and rapid population growth and associated urbanization have created numerous challenges for land and water managers.