Estimating the influence of water control infrastructure on natural low flow in complex reservoir systems: A case study of the Ohio River

Abstract

Study region:: The Ohio River in the northeast United States (US). Study focus:: Low streamflows are critical for urban water security, agricultural irrigation, water quality regulatory thresholds, navigation passage, and ecological well-being. However, there is insufficient understanding of the natural low flow conditions in rivers containing dams and artificial reservoirs, in part because we have inadequate records of natural flows prior to the introduction of the water control infrastructure. We demonstrate an improved technique for estimation of human impact on low flow, and describe the analytical innovations necessary to apply the technique. The primary innovation necessary was the development of a parsimonious streamflow routing algorithm to aggregate naturalized flow from reservoirs operated by the US Army Corps of Engineers (USACE) to locations of concern along the Ohio River mainstem. New hydrological insights for the region:: This study shows that, in dry years, releases from USACE reservoirs during autumn months account for up to approximately half of the mainstem flow, and the influence of USACE water control infrastructure is more pronounced on many of the Ohio River’s tributaries. The Flow Duration Curves also show significant differences in low flow throughout the mainstem. This has implications for dry season river functionality in all the categories listed above; if the infrastructure were to fail, or lose effectiveness due to climate change, these river functions would be threatened.

Keywords

• Drought
• 7Q10
• Dams
• Flow duration curve
• River routing
• Ohio River