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).