DETAW (Delta Evapotranspiration of Applied Water) is a computerized mathematical model of the Sacramento –San Joaquin Delta Service Area (DSA). It estimates both the consumptive water demands and the source of the water to meet the demand (precipitation, diversions, seepage from channels) on a daily time step for the historical hydrological period of water years 1922-2016. The historical consumptive demands use historical land use (where acreages change annually), and the projected consumptive demands assume a fixed land use for every year of the simulation (e.g., 1920 level, or 1950 level, 2000, 2050, etc.).