Water Resources Modeling Evaluation, for the Apalachicola, Chattahoochee, and Flint River Basin, Florida


For the Northwest Florida Water Management District (NWFWMD), HGL performed a comprehensive analysis of transient stream flow reduction caused by groundwater pumping in the Apalachicola, Chattahoochee, and Flint (ACF) River Basin in portions of Florida, Georgia, and Alabama. The starting point of this analysis was a U.S. Geological Survey (USGS) study that focused on steady-state conditions and addressed seasonal fluctuations in only a limited manner. HGL reviewed the USGS-developed groundwater model, including its adequacy for simulating the Floridan aquifer system and groundwater/surface water interactions. HGL extended the model and performed 55-year transient model simulations for 1995, 2010, and 2050 projections. These projections included both “expected” and “high” demands, as well as “dry” and “normal” conditions. Various future operating conditions were also analyzed for the ACF River reservoir system with respect to water supply and water quality. HGL used the U.S. Army Corps of Engineers’ HEC-5 model, along with a 55-year record of observed daily stream flows to evaluate the upper limits of available water after all reservoir uses, other than flood protection, had been satisfied.

Project Highlights
Extended the USGS-developed MODFE model for transient simulations to better define the reasonably expected regime of stream-aquifer flow reductions over the course of a typical growing season, taking into account recharge from the overburden that includes storage effects.
Provided expert assistance to NWFWMD in the setup, application, analysis, and review of the HEC-5 model for system alternatives and assistance in the application of the HEC-5Q model to evaluate water quality environmental conditions in the Apalachicola River and Bay.
Provided technical assistance to Florida’s General Counsel with respect to interstate compacts and contracts pertaining to water allocation and rights for Florida, Georgia, and Alabama.
Conducted a comprehensive analysis of water availability through development and calibration of a regional groundwater flow model using MODHMS® over Walton, Okaloosa, Santa Rosa, and Escambia Counties that included the Surficial and Floridan Aquifer Systems.