This data release provides a monthly irrigation water use reanalysis for the period 2000-20 for all U.S. Geological Survey (USGS) Watershed Boundary Dataset of Subwatersheds (Hydrologic Unit Code 12 [HUC12]) in the conterminous United States (CONUS). Results include reference evapotranspiration (ETo), actual evapotranspiration (ETa), irrigated areas, consumptive use, and effective precipitation for each HUC12. ETo and ETa were estimated using the operational Simplified Surface Energy Balance (SSEBop, Senay and others, 2013; Senay and others, 2020) model executed in the OpenET (Melton and others, 2021) web-based application implemented in Google Earth Engine. Results provided by OpenET/SSEBop were summarized to hydrologic response units (HRUs) in the National Hydrologic Model (NHM; Regan and others, 2019) to estimate consumptive use and effective precipitation on irrigated lands. Irrigated lands for the CONUS were provided by the Landsat-based Irrigation Dataset (LANID; Xie and others, 2019) for each year of the reanalysis period. Consumptive use estimates provided by the NHM were disaggregated to HUC12s using area weighted intersections with HRUs and the relative proportion of irrigated lands in each intersected area. The Landsat-based Irrigation Dataset (LANID) uses a random-forest machine-learning model with greenness and vegetative indices, climate data, and crop masks to identify irrigated crops (Xie and others, 2021, Xie and Lark, 2021). Separate western US and eastern US methods are used to train and validate the model. Annual LANID maps for 2018 -20 were created using the same techniques in Xie and others, 2021, and Xie and Lark, 2021.