Potential areas of groundwater discharge were delineated for the Humboldt River Basin to estimate groundwater evapotranspiration from phreatophyte vegetation, the primary component of natural groundwater discharge in the region. The boundary that defines the potential area of groundwater discharge represents the maximum spatial extent of groundwater discharge by phreatophyte vegetation, and areas within this boundary may discharge little to no groundwater where bare soil or sparse vegetation is the primary land cover. The boundaries are based on the original delineations of phreatophyte vegetation published in Reconnaissance Series Reports and Water Resource Bulletins for the state, which are also provided in this database with the filename "Historical_recon_and_wrb_phreatophyte_boundaries.shp". These data are meant to be used for estimating annual groundwater evapotranspiration following the methodology described by Beamer et al. (2013) and Huntington et al. (2022).