Evaluating climate change impacts in a heavily irrigated karst watershed using a coupled surface and groundwater model

Study region: Lower Apalachicola-Chattahoochee-Flint (ACF) River Basin of southeastern United States Study focus: The threats of climate change on the surface- and groundwater resources of the lower ACF River Basin of southeastern U.S. is an important concern for the long-term ecological as well as agricultural sustainability. This study developed a coupled SWAT-MODFLOW for the study region and evaluated the impacts of climate change projected under RCP4.5 and RCP8.5 emissions scenarios. New hydrological insights into the region: Evaluation of simulated streamflow and groundwater levels showed that SWAT-MODFLOW can adequately replicate the hydrology of a karstic watershed such as that present in the study domain even without the incorporation of conduit flows/karst features. Comparison to baseline conditions indicates a shift in the monthly streamflow pattern in the region with a reduction from April to June and increases in the rest of the year under future climate. The region will also likely see an increase in low-flow as well as high-flow events, thus increasing streamflow variability in the region. More frequent low flow conditions in the future can lead to increased drying of ephemeral streams threatening the ecological sustainability of the region due to habitat loss. This, along with the projected reduction in groundwater levels can lead to increased stress on water resources of the region for irrigation, thus threatening the agriculture sustainability and increasing water conflict between the neighboring states.