A comparison of watershed storage trends over the eastern and upper Midwestern regions of the United States, 2003-2015

Basin-scale groundwater storage trends calculated from long-term streamflow records provide insight into the evolution of watershed behaviors. Our study presents the first spatially relevant validation of recession-based trend approaches by comparing three independent storage trend estimates using GRACE-derived groundwater storage, in situ groundwater elevation observations, and recession-based approaches for the time period of 2003-2015. Results documented consistent agreement between spatially interpolated groundwater observation trends and recession-based storage trends, while GRACE-derived groundwater trends were found to exhibit variable, poor comparisons. A decreasing trend in watershed storage was identified in the southeastern U.S. while increasing trends were identified in the northeast and upper Midwest estimated from recession-based approaches. Our recession-based approach conducted using nested watershed streamflow records identified variable watershed storage trends at scales directly applicable for comparative hydrology studies and for assisting in watershed-based water resources management decisions.