This data set includes 1 km resolution monthly timescale estimates of the effective recharge component of the water budget over the time period from October 2003 - December 2015. These estimates were developed as water budget residuals using previously published data sets for other water budget components: PRISM precipitation (Daly et al., 2004), SNODAS snow water equivalent (National Operational Hydrologic Remote Sensing Center, 2004), SSEBop-WB evapotranspiration (Reitz et al., 2017), a map of groundwater-sourced irrigation (Reitz et al., 2017), and monthly surface runoff maps (Reitz et al., 2019). The recharge data were estimated as the difference between water supply (precipitation plus snow melt plus irrigation) and the other water budget components (snow accumulation, surface runoff, and ET) for a given month. In locations / months where the SNODAS snow accumulation data indicated greater snow accumulation than PRISM precipitation for that month, the snow accumulation was capped to the precipitation value. The monthly recharge maps represent the implications of these water budget component estimates on resulting recharge rates, and are not accompanied by an evaluative and interpretive journal article or report, so ought to be taken as preliminary estimates. The authors plan to follow this work with further efforts that will result in updated versions of monthly recharge maps, and accompanying interpretive and evaluative work. The data set here includes two versions of the monthly recharge maps. The raw version (e.g., "2003_raw.zip") includes negative values where the water budget component estimates for ET, runoff, and snow accumulation exceeded the water supply from precipitation and snow melt. The positive version (e.g., "2003_positive.zip") replaces these negative values with zeros. The positive version is the one that should be used for application of these data sets, but the raw version can be useful as an indication of the quality of the water budget estimates in a given location.