Coastal springs and seeps, including Rainbow Springs, a tributary of Withlacoochee River, discharge as much as a billion gallons of water per day to low-lying coastal swamps and estuarine marshes along the Guld Coast of Citrus and Hernando Counties, Florida. Although Weeki Wachee Spring has long been regarded as an obvious source of freshwater supply, long-term diversion of large volumes of water from Weeki Wachee River will cause encroachment of brackish water throughout the residential canals in the lower reach of the river to about 4.4 miles below Weeki Wachee Spring. Weeki Wachee Spring is analogous to a flowering well tapping an artesian aquifer. Flow characteristics of Withlacoochee River and Rainbow Springs indicate that about 600 cubic feet per second is available on a perennial basis, disregarding the downstream requirements for control of saltwater encroachment. (Woodard-USGS)