Irrigation is a requirement for productive crop growth in most of the agricultural areas of Idaho.  The determination of an allowable water-use period for irrigation should be based on the period when water can be beneficially applied to initiate or enhance crop growth.  Different crops will begin and end growth at different times of the year for a given location; those times will vary from year to year as well. Temperature and the availability of water are two important factors that influence the beginning and ending of growth for crops.  A temperature-based approach has been found to be a simple and adequate method to determine an allowable water-use period of irrigation.  A standard irrigation season map was developed to account for the temperature variations across the state.  The standard map will ensure that the allowable water-use period can be simply and consistently applied. The 45-degree average daily temperature threshold was selected as the basis for standard irrigation seasons because it provides for the longest allowable water-use period.

Irrigation is a requirement for productive crop growth in most of the agricultural areas of Idaho.  The determination of an allowable water-use period for irrigation should be based on the period when water can be beneficially applied to initiate or enhance crop growth.  Different crops will begin and end growth at different times of the year for a given location; those times will vary from year to year as well. Temperature and the availability of water are two important factors that influence the beginning and ending of growth for crops.  A temperature-based approach has been found to be a simple and adequate method to determine an allowable water-use period of irrigation.  A standard irrigation season map was developed to account for the temperature variations across the state.  The standard map will ensure that the allowable water-use period can be simply and consistently applied. The 45-degree average daily temperature threshold was selected as the basis for standard irrigation seasons because it provides for the longest allowable water-use period.