Seasonal streamflow enhanced unit runoff method estimates across the conterminous United States, 2000 through 2020

This data release contains seasonal streamflow estimates across the conterminous United States (2,691,587 NHDPlusV2 flowlines with defined from nodes) for 21 water years from November 1999 through December 2020. Streamflow was estimated using the Enhanced unit RunOff Method (EROM) following McKay and others (2012) with updated diversion representation and extended here to include seasonal estimates for each year. Monthly unit runoff from a water balance model (McCabe and Wolock, 2011) were used together with observed streamflow at 2,057 reference gages to estimate natural streamflow conditions at all ungaged reaches. Natural streamflow estimates were then adjusted for diversions and conditioned upstream and downstream to observed streamflow at all gages (5,875 in total including reference) to reduce error in the final streamflow prediction. Two seasonal definitions were applied, and two seasonal sets of streamflow predictions are provided in this data release. The first seasonal definition set winter as December, January, and February; spring as March, April, and May; summer as June, July, and August; and fall as September, October, and November. The second seasonal definition set winter as January, February, and March; spring as April, May, and June; summer as July, August, and September; and fall as October, November, and December. Data inputs and computer scripts are provided in this data release to fully reproduce streamflow results (see ReadMe_erom.txt for contents).