Supporting data for low-flow statistics computed for streamflow gages and methods for estimating selected low-flow statistics for ungaged stream locations in Ohio, water years 1975–2020

This data release comprises the tabular data used to develop regression equations for estimating selected low-flow statistics for ungaged streams in Ohio that are not substantially affected by regulation, diversions, or other anthropogenic influences, and the geographic information systems (GIS) layer to implement them in the U.S. Geological Survey StreamStats application (https://streamstats.usgs.gov).

A statewide recharge-based estimate of streamflow variability index (SVI) was used as an explanatory variable in developing many of the equations to estimate selected low-flow statistics at ungaged sites in Ohio and is included as part of this data release. Regressions, using SVI as the explanatory variable, were used to develop equations for predicting annual and seasonal minimum 1-, 7-, 30-, and 90-day mean flows with 10-year recurrence intervals, the harmonic mean flow, and the 80 percent duration flow. The resulting equations are presented in VonIns and Koltun (2024). To apply the equations to ungaged sites in Ohio, a raster (grid) of estimated streamflow variability index (SVI) for Ohio is included. The raster was developed using Environmental Systems Research Institute (ESRI) Spatial Analyst Software’s Empirical Bayesian kriging (EBK) geoprocessing function with at-gage computed SVIs used as the dependent variable and a recharge raster (grid) of estimated mean annual natural ground-water recharge (Wolock, 2003) as the explanatory variable. Other explanatory variables used to develop the equations and included in tabular form as part of this data release include decimal longitude and drainage area. A statewide coverage of decimal longitude and drainage area were not included as part of this data release because they are aleady available for ungaged streams within StreamStats.