Evaluating low flow patterns, drivers and trends in the Delaware River Basin

In the humid, temperate Delaware River Basin (DRB) where water availability is generally reliable, summer low flows can cause competition between various human and ecological uses. As temperatures continue to rise, population increases development expands, it critical understand historical flow variability anticipate plan for future flows. Using a sample of 325 U.S. Geological Survey gages, we evaluated spatial patterns in several metrics, biophysical climatic drivers these trends two periods: 1950–2018 1980–2018. We calculated annual 7-day date, deficit as departure below long-term daily threshold number discrete periods this threshold. also aggregated climate metrics watershed scale used existing properties quantifying land cover, topography, soils, geology, activity. Random forest models were assess hierarchy variable importance explaining mean-annual each metric using all gages. find muted regional variability, likely due myriad anthropogenic, landscape, modifications that obscure regimes from their natural characteristics. contrast, individual years show markedly different magnitude severity. Coincident with precipitation, have increased deficits decreased both 1980–2018 periods. However, Coastal Plain physiographic province use impervious area recent decades, highlighting effects management on With continued change expected DRB, additional research needs are highlighted enable estimation prolonged flow.