Local water year for 4-digit hydrologic unit areas across the conterminous United States

Identifying and predicting precipitation variability trends and their influence is sometimes challenged by the asynchrony between precipitation and water fluxes. To account for this asynchrony, scientists and managers use “water year” for estimating precipitation and its impacts on water flow and ecosystems. Although a variety of definitions have been proposed, those water years either did not consider areal variations in climate and hydrology or cannot be generalized to a macroscale. Using an existing definition where the water year begins in the month with the lowest average monthly streamflow, we developed a local water year (LWY) timeframe that considers spatial variations and can be applied at the continental scale. We employed a spatial interpolation technique to assign LWY start and end months to local areas (i.e., 4-digit hydrological unit areas, which are 4,384-134,755 km2 subregions) across the conterminous U.S. This dataset can be linked with diverse climate, terrestrial, and aquatic data for broadscale studies.