This data release accompanies the USGS Techniques and Methods report titled: "The Basin Characterization Model - A Regional Water Balance Software Package", and includes all necessary Basin Characterization Model version 8 (BCMv8) inputs and outputs for water years 1896 to 2023. The BCMv8 was refined from the previous BCMv65 version to improve the accuracy of the water-balance components, particularly the recharge estimate. The new version includes seven new features: (1) monthly vegetation-specific actual evapotranspiration (AET) for 65 vegetation types, (2) spatially distributed calibration coefficients for snow accumulation and snowmelt, (3) mapped soil organic matter, (4) soil hydraulic properties calculated from soil texture and soil organic matter (model simulations run using water content at field capacity of –0.01 megapascal (MPa) and wilting point of –6 MPa), (5) soil dry-out below wilting point at a rate driven by average statewide aridity, (6) a switch allowing for the incorporation of urban impermeable surfaces, and (7) internally calculated gaining and losing streams. The model has been run at a monthly time scale to calculate the unimpaired water balance for every 18-acre (270 by 270-meter) grid cell for all of California, including all basins draining into the State for water years 1896–2022. Version 2.0 Changes from previous version: 1) Added BCMv8 climate inputs and outputs for water year 2021 2) Updated climate inputs and outputs for water 2020 to correct error.
Version 3.0 Changes from previous version: 1) Added BCMv8 climate inputs and outputs for water year 2022 Version 4.0 Changes from previous version: 1) Added BCMv8 climate inputs and outputs for water year 2023