A Framework for Assessing the Effect of Irrigation Improvements: Economic Rivalry, Irrigation Abstraction, and Partition to Fates

Abstract

Responsible application of finite resources to infinite needs means that proposals for irrigation improvement must be weighed and assessed. The assessment requires an understanding of the changes in flux, and the social, ecological and economic effect of such changes. This paper is focused on evaluation of changes in flux, not discounting the vital components of weighing the implications of the changes. A useful criterion for the assessment of the flux implications of improvements to irrigation efficiency is the net effect to basin water supplies. The flux assessment can be performed with four necessary and sufficient exercises: (1) Consider irrigator response to the change; (2) Close the water budget on all changes in flux resulting from the irrigator response; (3) Consider the economic rivalry effects of the changes in flux; (4) Quantify changes in supply to all affected participants. This paper focuses on the effect that these four factors have upon water flow, with the implicit assumption that flow impacts ecosystem services, private user benefits, and social equity. Knowledge of changes in flow is a necessary but not a sufficient input to the evaluation of these factors. Irrigator response can be assessed based on an assumption of rational profit-maximizing behavior, and on the legal and social bases of water use. Closing the water budget can be performed using methods found in an extensive literature describing evaporation, transpiration, irrigation requirements, irrigation efficiency, and the various fates of the non-consumed fraction of field-applied irrigation water. The physical effects of irrigation improvements can be further partitioned using the concepts of economic rivalry. The framework presented allows policy makers to evaluate the effects that improvements will have not only upon the improved water use and the new use to which “saved” water will be devoted, but also to the secondary effects and beyond, upon human uses or ecosystem services that currently rely upon the “waste” stream resulting from nominally inefficient application and use. While it is acknowledged that evaluation of ecosystem services requires greater knowledge of ecosystem functions than is available in many basins, at least this framework calls attention to the services and provides a quantification of the flux of water delivered to them.