Evaluating Coastal Aquifer Recharge as a Barrier to Saltwater Intrusion and Improving Aquifer Water Levels

West Central Florida has exhibited declining groundwater levels in the Upper Floridan aquifer over the last 50 years in the area of southern Hillsborough County and western Polk County. These water level declines have caused saltwater intrusion along the coastal area of Hillsborough County. The Southwest Florida Water Management District (District) designated this area as the Southern Water Use Caution Area (SWUCA) to limit additional groundwater withdrawals and implemented a recovery strategy to mitigate the Most Impacted Area (MIA) that exhibited the greatest water level decline.

The District initiated an aquifer recharge feasibility study to identify recharge concepts that may provide the highest level of beneficial use of locally available reclaimed water flows. This study concluded that coastal aquifer recharge can be a viable permittable solution to support recovery of declining water levels in the SWUCA. The District implemented a regulatory water level mitigation policy that would allow groundwater mitigation offset credits to be earned for up to 90 percent of the regional water level improvements within the SWUCA which may be used to develop future water supplies further inland.

The county has taken the regional initiative by implementing an aquifer recharge pilot project to beneficially utilize available reclaimed water as a saltwater intrusion barrier and for the improvement of aquifer water levels. The pilot project includes construction and injection testing of an aquifer recharge well and development of a semi-regional variable-density groundwater model to assess the system’s ability to impede saltwater intrusion and improve aquifer water levels. The pilot project will also evaluate the potential for mobilization of arsenic within the aquifer recharge zone during operation of the recharge system.

This presentation will explain site hydrogeology, conceptual site model, and numerical model development, as well as the results that will be used to evaluate the regional aquifer recharge system.