The following computer application programs have been cooperatively developed and released between California Department of Water Resources and the University of California, Davis. These programs consist of the Consumptive Use Program PLUS, the original Consumptive Use Program (CUP) and the Simulation of Evapotranspiration of Applied Water (SIMETAW).

Click the images below to download the latest version of the models.

Consumptive Use Program+ (CUP+) - The CUP+ program is an MS-Excel application written to make accurate estimates of both crop evapotranspiration (ETc) and evapotranspiration of applied water (ETaw), which is a seasonal estimate of the irrigation water requirement for evapotranspiration of a crop minus any water supplied by effective rainfall and effective seepage. In addition to using monthly climate data, the program uses daily measured weather data to estimate daily soil water balances for surfaces that account for ET losses and water contributions from rainfall, seepage, and irrigation. Soil water-holding characteristics, effective rooting depths, and irrigation frequency are used with rainfall and ETc data to calculate a daily water balance and determine effective rainfall and ETaw, which is equal to the seasonal cumulative ETc minus the effective rainfall. ETaw information is needed to determine the demand side of water requirements. The application also can be used to study the impact of climate change on evapotranspiration and irrigation water needs. It outputs a wide range of tables and charts that are useful for irrigation planning.

Consumptive Use Program (CUP)  - CUP was developed to help growers and water agencies determine their crop coefficient (Kc) and crop evapotranspiration (ETc) values. By using newly improved methods, CUP computes ETo using the daily Penman-Monteith equation, and then it uses a curve fitting technique to drive one year of daily weather and ETo data from monthly data. In addition, the program accounts for rainfall, cover crops, and immaturity factors for estimating crop evapotranspiration. 

SIMETAW - The SIMETAW program was developed to help water planners and researchers to improve their long term estimates of net crop water requirements. This program can simulate many years of weather data from monthly climate data and to estimate reference evapotranspiration (ETo) and crop evapotranspiration (ETc) with the simulated data. In addition, simulated daily rainfall, and soil crop information are used to determine effective rainfall and ET of applied water (ETaw), where ETaw is an estimate of the crop evapotranspiration minus any water supplied by effective rainfall. The simulation program allows one to investigate how climate change might affect water demand. In addition, the use of the widely adopted Penman-Monteith equation for reference evapotranspiration (ETo) and improved methodology to apply crop coefficients for estimating crop evapotranspiration is used to improve ETaw accuracy.

SC-SIMETAW - The South Coast Simulation of Evapotranspiration of Applied Water (SC-SIMETAW) was specifically designed to evaluate the Department's Surface Storage Program work. The application simulates daily weather data from monthly means from PRISM and estimates daily soil water balances for surfaces within the South Coast region that account for evapotranspiration losses and water contributions from rainfall and irrigation. It computes daily reference evapotranspiration (ETo), crop coefficient factors (Kc), crop evapotraspiration (ETc), daily water balance, effective rainfall, evapotranspiration of applied water (ETaw), etc. for agricultural crops and warm-season grass within each of the 13 DAUs (Detail Analysis Unit) in the South Coast region for the water years 1922-2003. The results of this study will allow the Department’s Least-Cost Planning Simulation (LCPSIM) Model to better simulate regional urban water management operations in the South Coast.

California Weather Data - The California Weather Data program was developed in Microsoft Excel to provide daily mean weather and ETo data from CIMIS to input into the CUP and SIMETAW models. (xls: 3.52 MB - 635 KB ZIP)