Anthropogenic and Climate Impacts on Groundwater Resources in the Lower Apalachicola-Chattahoochee-Flint River Basin

Abstract

El Niño Southern Oscillation (ENSO) is one of the major climate variability cycles around the world and is responsible for droughts in the Southeast United States. These ENSO-induced droughts have been responsible for agricultural losses, water disputes and promotion of water restrictions in the Southeast. In the Apalachicola- Chattahoochee-Flint (ACF) River Basin, in addition to drought, rapid population growth, urban sprawl, and increased agricultural production are threatening the availability of freshwater resources and causing endangered species concerns. As a result, Alabama, Georgia, and Florida have been fighting over the allocation of ACF River Basin water for the past two decades. The water conflict heats up every time there is drought in the basin. This research was conducted to study the effects of ENSO-induced droughts and irrigation pumpage on groundwater levels and groundwater budget components of the Upper Floridan Aquifer (UFA) in the lower ACF River Basin. Results indicate that ENSO exhibits teleconnection with groundwater levels in the UFA. The teleconnection was more prominent during the winter season. The study also found that prolonged droughts severely affect groundwater levels and the groundwater recovery periods can be as much as 2 years. The groundwater model, MODular Finite-Element Model (MODFE), was used to study the effect of irrigation water withdrawal during droughts years of 2010 – 2012. The results showed that groundwater levels and stream-aquifer flux are affected by irrigation water withdrawal. Most of the irrigation water pumped is contributed by loss in aquifer storage and losses in stream-aquifer flux. The results also showed that irrigation during the year 2012 resulted in groundwater levels to fall by as much as 6 ft, and in areas with endangered species concerns. Finally, MODFE was also used to study the effect of possible future increased irrigation levels on groundwater levels and stream-aquifer flux in the study area during the drought water year of 2012. The effect of application of irrigation restrictions in vulnerable regions was also studied. Results showed that elevated irrigation levels severely affect groundwater levels in the vulnerable regions. Doubling of irrigation resulted in as much as 11 ft decline in groundwater levels in the Spring Creek subwatershed. Additionally, the study also found that irrigation water-withdrawal exhibits a linear relationship with stream-aquifer flux in the study area.