This data release documents the datasets and procedures used to update the Los Angeles Basin Watershed Model (LABWM) (Hevesi and Johnson, 2016) from INFIL3.0 (USGS, 2008a, 2008b) to INFIL4.0. The LABWM provides gridded monthly infiltration, evaporation, recharge, and runoff estimates for the Los Angeles region using the water balance recharge model, INFIL. INFIL is a grid-based, distributed-parameter, deterministic model that uses a daily time step to simulate the temporal and spatial distribution of the root-zone water balance, including net infiltration and potential recharge across the lower boundary of the root zone. INFIL3.0 was originally released and documented in 2008 (USGS, 2008a) and has been used and documented in several studies as the water-balance model used to develop spatially and temporally distributed estimates of recharge and runoff (Rewis and others, 2006; Hevesi and Christensen, 2015; Flint and Martin, 2012; Nishikawa and others, 2005; Hevesi and others, 2003; Paulinski, 2021a) including the LABWM (Hevesi and Johnson, 2016). The LABWM used the INFIL3.0 code with estimates of urban (landscape) irrigation to simulate the near-surface water balance from water years 1905 to 2014 for the Los Angeles Basin Watershed (Hevesi and Johnson, 2016) and to develop components of the recharge boundary condition for the Los Angeles Coastal Plain Groundwater Model (Reichard and others, 2003; Paulinski, 2021). Recently, there has been increased interest from stakeholders to update the Los Angeles Coastal Plain Groundwater Model (LACPGM) and thus there is a need to update the associated LABWM to include water years 2015 to 2020. To provide the updated water balance and recharge estimates, the INFIL3.0 code used in Hevesi and Johnson (2016) needed a modification to allow simulations to run past water year 2014. The modification made to update INFIL3.0 that result in the creation of INFIL4.0 involved increasing the array dimensions used for daily input variables, including precipitation, maximum and minimum air temperature, and surface water inflow, to allow for the increase in the total number of days in the extended simulation period (water years 1905 through 2020). The model archive included with this data release of the updated LABWM using INFIL4.0 includes the INFIL4.0 Fortran source code, the compiled INFIL4.0 executable file and related batch file, all input files needed to run the model from water year 1905 to 2020 for the 12 subdomains used in the LABWM, all simulation outputs for all subdomains, and a post-processing script (Monthmap). In addition to calculating the total potential recharge from contributing recharge areas outside the LACPGM boundary and recharge from interior LACPGM cells, the Monthmap script performs unit conversions (from millimeters per month to feet per day) and clips the output grid to match the areal extent of the LACPGM grid (Paulinski and others, 2021b).

This data release contains monthly 270-meter gridded Basin Characterization Model (BCMv8) climate inputs and hydrologic outputs for Los Angeles (LA). Gridded climate inputs include: precipitation (ppt), minimum temperature (tmn), maximum temperature (tmx), and potential evapotranspiration (pet). Gridded hydrologic variables include: actual evapotranspiration (aet), climatic water deficit (cwd), snowpack (pck), recharge (rch), runoff (run), and soil storage (str). The units for temperature variables are degrees Celsius, and all other variables are in millimeters. Monthly historical variables from water years 1896 to 2019 are summarized into water year files and long-term average summaries for water years 1981-2010. Four future climate scenarios were spatially downscaled from 6 kilometers to 270 meters, and run through the BCMv8 using the same model parameters. The future climate scenarios are all Representative Concentration Pathway (RCP) 8.5 and include: CanESM2, CNRM-CM5, HadGEM2-ES, and MIROC5 from California's Forth Climate Change Assessment. Future climate scenarios span from water year 2007 to 2099, and monthly variables were summarized by water year and the average 2070 to 2099 period. Streamflow for each calibration basin was calculated using a post processing Excel spreadsheet and BCMv8 recharge and runoff, and are provided in tabular comma separated *.csv files. Raster grids are in the NAD83 California Teale Albers, (meters) projection in an open format ascii text file (*.asc).

This data release contains monthly 270-meter gridded Basin Characterization Model (BCMv8) climate inputs and hydrologic outputs for Los Angeles (LA). Gridded climate inputs include: precipitation (ppt), minimum temperature (tmn), maximum temperature (tmx), and potential evapotranspiration (pet). Gridded hydrologic variables include: actual evapotranspiration (aet), climatic water deficit (cwd), snowpack (pck), recharge (rch), runoff (run), and soil storage (str). The units for temperature variables are degrees Celsius, and all other variables are in millimeters. Monthly historical variables from water years 1896 to 2019 are summarized into water year files and long-term average summaries for water years 1981-2010. Four future climate scenarios were spatially downscaled from 6 kilometers to 270 meters, and run through the BCMv8 using the same model parameters. The future climate scenarios are all Representative Concentration Pathway (RCP) 8.5 and include: CanESM2, CNRM-CM5, HadGEM2-ES, and MIROC5 from California's Forth Climate Change Assessment. Future climate scenarios span from water year 2007 to 2099, and monthly variables were summarized by water year and the average 2070 to 2099 period. Streamflow for each calibration basin was calculated using a post processing Excel spreadsheet and BCMv8 recharge and runoff, and are provided in tabular comma separated *.csv files. Raster grids are in the NAD83 California Teale Albers, (meters) projection in an open format ascii text file (*.asc).

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 2024. 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 1896–2024. First release: January 19, 2021 Version 2.0: February 2023 Version 3.0: June 2023 Version 4.0: May 2024 Version 5.0: June 2025

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

This dataset represents locations of major inflows to the CA Central Valley. All but the two southernmost locations are associated with CalSim II. CalSim II is an operations model for estimating State Water Project and Central Valley Project Deliveries of surface water. CalSim II was used as part of the CA Water Commission Water Storage Investment Program (WSIP) to estimate projected deliveries associated with projected Climate Change Conditions. The related records are for model results from the 2030 Central Tendency, 2070 Central Tendency, 2070 Dry-Extreme Warming and 2070 Wet-Moderate Warming projections. All projections are based on an ensemble of 10 GCMs using two different emissions scenarios (RCP 4.5 and RCP 8.5).

This dataset represents locations of major inflows to the CA Central Valley. All but the two southernmost locations are associated with CalSim II. CalSim II is an operations model for estimating State Water Project and Central Valley Project Deliveries of surface water. CalSim II was used as part of the CA Water Commission Water Storage Investment Program (WSIP) to estimate projected deliveries associated with projected Climate Change Conditions. The related records are for model results from the 2030 Central Tendency, 2070 Central Tendency, 2070 Dry-Extreme Warming and 2070 Wet-Moderate Warming projections. All projections are based on an ensemble of 10 GCMs using two different emissions scenarios (RCP 4.5 and RCP 8.5).

This dataset represents locations of major inflows to the CA Central Valley. All but the two southernmost locations are associated with CalSim II. CalSim II is an operations model for estimating State Water Project and Central Valley Project Deliveries of surface water. CalSim II was used as part of the CA Water Commission Water Storage Investment Program (WSIP) to estimate projected deliveries associated with projected Climate Change Conditions. The related records are for model results from the 2030 Central Tendency, 2070 Central Tendency, 2070 Dry-Extreme Warming and 2070 Wet-Moderate Warming projections. All projections are based on an ensemble of 10 GCMs using two different emissions scenarios (RCP 4.5 and RCP 8.5).

The hydrologic modeling approach used to predict functional flows relies on daily streamflow data from gages operated by the U.S. Geological Survey (USGS) in California. This dataset contains, for each of 219 gages, a collection of metrics computed on each water year for the period of record to and including Water Year 2016.

The hydrologic modeling approach used to predict functional flows relies on daily streamflow data from gages operated by the U.S. Geological Survey (USGS) in California. This dataset contains, for each of 219 gages, a collection of metrics computed on each water year for the period of record to and including Water Year 2016.