A tool for drought planning in Oklahoma: Estimating and using drought-influenced flow exceedance curves

Abstract

Study region: The study region is the state of Oklahoma, USA, which has a varied climate. Precipitation increases west to east, and temperature decreases south to north across the state. Accordingly, Oklahoma has been divided into nine Climate Divisions, which reflect those climatic as well as regional differences in agricultural practices. Study focus: Surface water is the dominant source for public water systems in Oklahoma and these supplies may be impacted by drought or climatic change. Hydrologic modeling is an important component of water resource planning, but may be beyond the budget of smaller communities. To create a freely available tool for initial assessment of drought streamflows, this study uses publicly available long-term precipitation records for climate divisions in Oklahoma to create flow duration curves (FDCs) from the drought-influenced subsets of streamflow records. New hydrological insights for the region: The FDCs created from those subsets showed increased likelihood of reduced streamflows. The reduced flows were shown to increase water supply risk to run-of-river users. To eliminate the need for users to re-create these analytic steps, study results were compared to published FDCs and reasonable estimates of drought-influenced FDCs were produced by offsetting the expected exceedance by 10%.

Keywords

• Drought
• Flow duration curve
• Oklahoma
• Streamflow
• Water supply