DEFICIT IRRIGATION .2. OBSERVATIONS IN COLUMBIA BASIN

A companion paper demonstrates that deficit irrigation can be profitable when irrigation costs are high or water supplies are limited. The present paper provides specific examples of deficit irrigation practices in the Columbia Basin with the aim of developing a better understanding of the practice and economic merits of this irrigation-management technique. The fundamental concepts developed in the companion paper are illustrated with data from nine cooperating farms. The economic analyses account for all costs of production, including the following: (1) Variable costs of irrigation; (2) variable costs not directly associated with irrigation operations; and (3) capital and other fixed costs of production. The second and third cost categories were of greater importance to the analysis than were the direct costs of irrigation. Estimates of average 10-year incomes were derived from farm data. Based on these estimates, farms that were practicing deficit irrigation achieved lower net incomes per hectare but higher net incomes per unit of applied water than the fully irrigated farms. This suggests that their irrigation practices were nonoptimal, but that they were benefiting financially from deficit irrigation. © ASCE.