Simulated irrigation reduction improves low flow in streams—A case study in the Lower Flint River Basin

Abstract

Study region: The Ichawaynochaway Creek watershed within the Lower Flint River Basin in the Southeast US. Study focus: Freshwater resources are facing increasing pressure globally, even in areas not generally accustomed to water shortages. The Apalachicola-Chattahoochee-Flint River basin has experienced episodic water stress over the past three decades due to population growth, climate variability, land use change, and agricultural intensification. While precipitation in the region is relatively high, declines in streamflow suggest a growing need to develop water management options focused on reducing water consumption. Many efforts have focused on reducing water use by irrigation, the primary water consumer in the region; however, the effectiveness of irrigation reduction at restoring streamflow is uncertain. New hydrological insights of the region: We used the Soil and Water Assessment Tool to simulate the effects of a range of irrigation reduction scenarios on streamflow during a 16-year period that included extreme drought and extremely wet conditions. Simulated irrigation reduction had a consistently positive effect on streamflow. In the absence of irrigation, annual streamflow increased 7 %, or ∼6 million m3/year, compared to normal irrigation. Proportional changes in streamflow were much greater during low flow periods. Additional flow during extremely low flow periods is critically important for conserving imperiled aquatic species and maintaining healthy stream habitats. Results indicate that increased flow is achievable by broadly implementing existing water conservation technologies. Keywords: Irrigation reduction, Streamflow, Flint River, SWAT, Environmental flows, Center-pivot