Coastal aquifers are susceptible to a variety of salt water intrusion forms, including lateral intrusion, upconing, and downward infiltration of brackish water. Recent advances in the development of practical integrated groundwater models make it possible to simulate these forms of salt water intrusion in support of coastal water supply planning and coastal aquifer management programs. Three dimensional groundwater flow models, dual phase sharp interface intrusion models, radial upconing models, and single phase contaminant transport models are being successfully applied to meet regulatory permit requirements, to develop coastal aquifer management plans, and to support water supply planning.
This paper discusses salt water intrusion modeling and its successful application for both water supply planning and consumptive use permitting. A case study is discussed to highlight some of these techniques in a project situation. The study highlights salt water intrusion modeling for a water supply company in the western part of Florida. Relying on wells located along the coast of the Gulf of Mexico tapping the limestone formations of the Floridan Aquifer, the supplier is vulnerable to both lateral salt water intrusion in the Upper Floridan Aquifer, as well as upconing of salt water from the saline Lower Floridan Aquifer. The Northwest Florida Water Management District (NWFWMD) required extensive, regional groundwater flow modeling, sharp interface salt water intrusion modeling, and the development of well field specific upconing models to support an application for a new well permit. An integrated suite of models was used to assess the threat to the coastal wellfield, to locate potential new well locations, and to provide the required estimates of the vulnerability of the selected new wellfield sites to eventual salt water intrusion.