Economic Analysis Approach for Identifying Optimal Microirrigation Uniformity

Abstract

Nonuniform pressure of microirrigation systems negatively impacts crop productivity, water utilization, and nonpoint source pollution. However, achieving network pressure uniformity can be prohibitively expensive. This paper presents an economic optimization method that seeks to balance competing costs and benefits. A custom computer software script is developed to implement the method and an irrigation case study is presented. Regression analysis showed that the relationship between economic efficiency and Christiansen uniformity (CU) is a cubic function with an optimum uniformity (i.e., in reference to CU) at 0.78 for cotton and 0.86 for olive trees. The results also indicate that water cost is the most important factor influencing total cost and economic efficiency, and next is capital cost. Also, irrigation systems with a relatively small subunit size (0.1–0.42 ha for cotton and 0.72–2.16 ha for olive) commonly lead to a high economic efficiency. Finally, to guarantee adequate uniformity, the most efficient microirrigation system design will necessarily use the smallest possible size of the manifold.