Rainfall-Runoff Time Lags from Saltwater Interface Interactions in Atlantic Coastal Plain Basins

The dynamic behavior of the freshwater-saltwater interface (FSI) in coastal aquifers can introduce unexpected lags between recharge and stream discharge, especially when is forced by long-term cyclical precipitation patterns. This work seeks to assess these FSI impacts at watershed scale. Recharge-discharge time were evaluated 68 watersheds overlying Floridan Aquifer System region southeastern United States (Florida, Georgia, South Carolina). Utilizing strength Atlantic multidecadal oscillation (AMO) signal this region, 10–20 year averaged discharge series used for selected watersheds. Lags 10–25 years found 16% basins considered, possibly induced a which responded slowly AMO-scale signal. Freshwater storage coefficients (S) estimated from change-in-storage groundwater level, with 11 showing S>1.5 indicating water well above that expected unconfined aquifers. These both recharge-discharge high S values showed positive linear relationship lag depth slope 0.016 yr/m (R-squared = 0.30). large may be directly impacting management as they obscure solute mass balances US.