1Evapotranspiration ETo is an estimate of atmospheric demand and is a useful reference point when determining plant irrigation need. ETa is an estimate of the water lost when a plant transpires or "sweats "through its leaves plus the water evaporated from the soil surface. This value is always a percent of ETo and varies according to species and other factors.

2 California Department of Water Resources, Captured Rainfall: Small-Scale Water Supply Systems, Bulletin 213. May 1981.

3 The tables are for determining potential storage, they are not for weather prediction. Weather may vary from the average at any time.

4 Household water collected from sinks, showers, washing machines for reuse as landscape irrigation. In Arizona greywater systems require a permit from the Arizona Department of Environmental Quality.