This dataset is part of the National Water Census ongoing development of best estimates of daily historical water budgets for over 100,000 hydrologic units across the United States. In this release, estimates of total flow and snowmelt for each hydrologic unit are added to the already released estimates of actual evapotranspiration, snowpack water-equivalent storage, soil moisture, recharge, streamflow, and precipitation. All these estimates are made available per twelve-digit hydrologic unit code watershed as contained in the NHDPlus v2.1 dataset and associated Watershed Boundary Dataset (WBD) snapshot. As this project progresses, it is expected that a complete closed water budget generated from the same water budget model will succeed this data release. Users are advised to ignore the first two years of the simulations to account for model initialization.<br /><br /> For background on source data and generation of these water budget variables, see nhru_hru_outflow.csv and nhru_snowmelt.csv from:<br /><br /> Hay, L.E. and LaFontaine, J.H., 2020, Application of the National Hydrologic Model Infrastructure with the Precipitation-Runoff Modeling System (NHM-PRMS), 1980-2016, Daymet Version 3 calibration: U.S. Geological Survey data release, https://doi.org/10.5066/P9PGZE0S <br /><br /> The water budget variables were converted to a HUC12 basis using area-weighted spatial interpolation. The HUC12 version is the one included with WBD snapshot associated withe NHDPlus v2.1. All code used for conversions are published by Blodgett (2020) referenced below.<br /><br /> Summary of files included:<br /> 1) hu12_ids.csv.zip - twelve digit hydrologic unit (HUC12) code identifiers used in all files.<br /> 2) timesteps.csv.zip - timesteps used in all files.<br /> 3) nhm_total_flow_timeseries.csv.zip - One HUC12 per row, one date per column, version of total flow data.<br /> 4) nhm_snowmelt_timeseries.csv.zip - One HUC12 per row, one date per column, version of snowmelt data.<br /><br /> This data release compliments the following related data releases:<br /><br /> Actual evapotranspiration and snowpack water equivalent storage:<br /> Blodgett, D.L., 2020, Twelve-digit hydrologic unit actual evapotranspiration and snowpack water equivalent storage from the National Hydrologic Model Infrastructure with the Precipitation-Runoff Modeling System 1980-2016: U.S. Geological Survey data release, https://doi.org/10.5066/P9IH7CB8.<br /><br /> Soil moisture and recharge:<br /> Blodgett, D.L., 2019, Twelve digit hydrologic unit soil moisture and recharge from the National Hydrologic Model Infrastructure with the Precipitation-Runoff Modeling System: U.S. Geological Survey data release, https://doi.org/10.5066/P9ZZAWK4.<br /><br /> Streamflow:<br /> Russell, A.M., Over, T.M., and Farmer, W.H., 2018, Statistical daily streamflow estimates at HUC12 outlets in the conterminous United States, Water Years 1981-2017: U.S. Geological Survey data release, https://doi.org/10.5066/P9DPSY6G.<br /><br /> Precipitation:<br /> https://www.sciencebase.gov/catalog/item/52a7bed0e4b0de1a6d2dd0fd <br /> Thornton, P.E., Thornton, M.M., Mayer, B.W., Wei, Y., Devarakonda, R., Vose, R.S., and Cook, R.B., 2017, Daymet—Daily surface weather data on a 1-km grid for North America, Version 3: ORNL DAAC website, accessed March 8, 2017, at https://doi.org/10.3334/ORNLDAAC/1328.