Average Estimates of Water-Budget Components Based on Hydrograph Separation and PRISM Precipitation for Gaged Basins in the Appalachian Plateaus Region, 1900-2011

As part of the U.S. Geological Survey’s Groundwater Resources Program study of the Appalachian Plateaus aquifers,
estimates of annual water-budget components were determined at 849 continuous-record streamflow gaging stations
from Mississippi to New York. Base flow, which can serve as a proxy for annual recharge, streamflow, and runoff
were estimated from computer programs—PART (Rutledge, 1993), HYSEP (Sloto and Crouse, 1996), and BFI
(Wahl and Wahl, 1988)—that are included in the hydrograph analysis component provided with version 1.0 of the
U.S. Geological Survey Groundwater Toolbox. Only complete years (January to December) of record at each
gage were used to determine annual estimates. Estimates of base-flow index, which is the percentage of
streamflow from base flow, are included in the annual and average tables. Precipitation was estimated by
calculating the average of cell values in the PRISM dataset intercepted by basin boundaries where previously
defined in the GAGES-II dataset (Falcone, 2011). Estimates of evapotranspiration were then calculated from
the difference between precipitation and streamflow.