The updated Central Valley Hydrologic Model (CVHM2) is similar to the original Central Valley Hydrologic Model (CVHM) in terms of the basic units of model discretization. Both versions simulated monthly stress periods on the same one square mile cell spatial discretization. Although the simulation period for CVHM1 was water years 1962-2003, the CVHM2 simulation period is water years 1962-2019. Both CVHM and CVHM2 have a 6 month spin up period from April-September of 1961. The CVHM2 is now composed of 13 layers compared to the ten in the CVHM. As in CVHM, hydraulic properties are generally based on percentage of coarse-grained deposits and these values are adjusted based on depth, spatial location (geomorphic province), and geologic units as described by Faunt and others (2009).