Irrigation sagacity: a measure of prudent water use

Abstract

Within the western United States, water rights are granted for reasonable and beneficial water use, and a measure of irrigation performance that embodies this standard is needed. A new performance parameter, irrigation sagacity (IS), is recommended for this purpose. The term `sagacity' comes from `sagacious', meaning wise or prudent. IS is more closely tied to the water rights granted, and to the potential for water conservation and reallocation than is the traditional irrigation efficiency, which considers only beneficial uses. Sagacious uses are either beneficial, or non-beneficial but reasonable. Reasonable uses are those that, while not directly benefiting agronomic production within the boundaries of the water rights area, are nonetheless justified under prevailing conditions. Non-sagacious uses (non-beneficial and unreasonable) are those uses which are without economic, practical, or other justification. Determination of sagacity involves checking alternate irrigation practices for practical, technical, economic, and environmental feasibility. Feasibility includes the requirement for a reasonable implementation schedule for any new practices. Only if a feasible alternate using less water is found should a current practice be considered in any part non-sagacious. The results of a sagacity determination may vary depending on geographic scale, time frame, and perspective.