WATER BUDGET METHODOLOGY

The District uses a precise water budget calculation to create its budgets.

Only developed (landscaped) areas are used to calculate the water budget. CCWD uses real time ETo data from the local California Irrigation Management Information System (CIMIS) station.

The District also calculates water demand for the turf areas and other plant material separately due to their different water demands. These are referred to as Plant Factors.

Different plant factors are used for each of the two plant types for each month of the year. This accounts not only for the difference between the plant types, but for the different demands during the year, based on the annual growth cycle. The budget also takes into account rainfall and how much of that water can be stored in the root zone of that water use group.

Finally, the efficiency of the irrigation system is taken into account, recognizing that no irrigation system can be 100 percent efficient.

The equation used in the CCWD water budget program is:

Site Water Budget = (Actual ETo x Kl) - ER x Area / IE x CF

Where:
Eto = Daily Reference Evapotranspiration
Kl = Landscape Coefficient (used to adjust ETo to monthly water needs of turf and non-turf)
ER = Effective Rainfall (portion of usable daily rainfall)
Area = Measurement of the square footage of turf and non-turf
IE = Irrigation Efficiency (increases water budget to account for system inefficiencies.)
CF = Conversion factor to put result into HCF per time period