WATER DUTY FOR AGRICULTURE IN THE WESTERN UNITED STATES.

The agricultural water duty is a measure of the quantity of water reasonably required for use in agricultural crop production. For some time in the western United States, the agricultural water duty has been used in the settlement of allocational disputes, adjudication proceedings, canal sizing, for conservation programs, and irrigation scheduling. This paper presents a very brief inquiry into the definition and use of the water duty as an allocator of water to agriculture in the western United States. The objectives of the paper are threefold: (1) to examine the existing definitions of the water duty concept, (2) to analyze the scientific bases of the water duty, and (3) to describe the implementation of the concept by the Arizona Department of Water Resources within the Tucson Active Management Area.