Study region: Apalachicola-Chattahoochee-Flint (ACF) Basin in the Southeast US
Study focus: Operational rules of managed river systems are typically developed based on historical hydrology. This approach fails to consider alternative plausible hydrologic conditions that may occur outside the observational period-of-record. Here, we evaluated operational rules of a transboundary managed river system—the ACF Basin—with multiple reservoirs under historical observations and 100 stochastic streamflow realizations representing the current streamflow conditions of the basin. These scenarios, which had comparable averages as the historical records but greater extremes, were simulated by coupling a stochastic streamflow model with a basin-wide river system model. We used these scenarios to evaluate the response of the ACF Basin against metrics for urban water supply, required freshwater inflows, floodplain forest ecosystem water needs and hydropower generation. The evaluation was done based on the magnitude, frequency, duration and seasonality of these metrics.
New hydrological insight of the region: The unique aspect of this paper is using a stochastic streamflow model coupled with a river basin model to evaluate the response of the ACF Basin’s current operational rules under several hypothetical plausible stationary hydrologic scenarios. We found that, overall, the basin response in terms of all the metrics used here was less favorable under the alternative stationary hydrologic scenarios than the historical hydrology. Our evaluations suggested that the reservoir operational rules should be revisited to consider a broader range of plausible hydrologic conditions.