Abstract: A system and method for using evapotranspiration (ET) and/or predicted precipitation data in controlling automated and semi-automated irrigation systems. In accordance with the present invention, meteorological data is monitored and used to adjust watering schedules for an irrigation site. A central computer uses the meteorological data and ET data to compute a watering factor. The watering factor represents the difference between a reference watering schedule (which can be stored at the irrigation site) and a new watering schedule. The new watering schedule can be based on similar climatic conditions of a geographic area in which the irrigation site is located. The watering factor is then sent to the irrigation site, which uses the watering factor to modify the reference watering schedule, if appropriate.

Abstract: A method and apparatus for using predictive evapotranspiration (ET) and precipitation data in controlling automated and semi-automated irrigation systems. In accordance with the present invention, the conventional use of ET values is modified to take into account predicted or forecast weather events. By using forecast weather data in computing ET values, a substantial savings in water use can be achieved. Past or historical meteorological data is used to make corrective adjustments to the watering schedules that have been predicted using meteorological forecasting. That is, as each day becomes past or historical, adjustments to the overall cumulative depletion of water in the soil need to be made. When an irrigation site is to be updated with a new watering schedule, actual meteorological data is first used to correct any differences between the previously forecast and actual meteorological data to the current day.