Datasets used to map the base-flow recession time constants in the Niobrara National Scenic River in Nebraska, 2016-18

The base flow recession time constant (tau) is a hydrologic index that characterizes the ability of a ground-water system to supply flow to a stream draining from that system. Tau and other correlated hydrologic indices have been used as explanatory variables to greatly improve the predictive power of low-flow regression equations. Tau can also be used as an indicator of streamflow dependence on groundwater inflow to the channel. Tau values were calculated for 10 streamgages in the Niobrara National Scenic River study area. The calculated tau values were then used to create a kriged map. Kriging is a geostatistical method that can be used to determine optimal weights for measurements at sampled locations (streamgages) for the estimation of values at unsampled locations (ungaged sites). The kriged tau map could be used (1) as the basis for identifying areas with different hydrologic responsiveness, with differing potential to demonstrate the effects of management changes and (2) in the development of regional low-flow regression equations. The Geostatistical Analyst tools in ArcGIS Pro version 2.5.2 (Environmental Systems Research Institute, 2012) were used to create the kriged tau map and perform cross validation to determine the root mean square error (RMSE) of the tau map.