5. An economic analysis of irrigation systems.
Irrigation Science, 11, 1990, pp. 37-43
The objective of this paper is to determine the economically optimal irrigation system for a set of conditions which are specified.
Irrigation systems are evaluated based on their performance and costs in relation to cotton production and drainage volumes. The latter factor is becoming increasingly important in some irrigated lands such as in the San Joaquin Valley of California where appropriate disposal of subsurface drainage water may become very expensive because of the total dissolved solids and presence of toxic elements in the drainage water.
Cotton was selected as the crop for analysis because it is a major crop on irrigated lands and it is amenable to irrigation by several systems.
Furthermore, it is a principal crop grown in the western San Joaquin Valley of California which will serve as a case study for the report.
An array of irrigation systems are available which can be broadly classified as being gravity flow or pressurized. Pressurized irrigation systems provide better control on the amount of applied water and, in most cases, better irrigation uniformity than gravity flow systems. They also have a higher initial capital cost than gravity flow systems and an analysis is required to determine whether the improved performance of pressurized systems justifies the additional costs. An economic analysis was done on several irrigation systems which included consideration of farm management costs associated with a given irrigation system, shifts in crop yield and drainage volumes associated with the optimal management of each irrigation system, and costs associated with disposal of drainage waters. Irrigation uniformity is a significant determinant to the results. Although irrigation uniformities can be highly variable based on design, maintenance and management, a typical uniformity for each irrigation system was selected. For the conditions of the analysis, gravity flow systems were calculated to be more profitable than pressurized systems if there was no constraint on the amount of drainage water generated or cost for its disposal. Imposition of costs for drainage water disposal induced a shift whereby pressurized systems became more profitable than gravity flow systems.
Irrigation systems can be broadly classified as being either gravity flow or pressurized.
Because of the limited number of irrigations, a furrow system might be very difficult to manage in a manner to obtain the desired drainage volume without missing the mark considerably resulting in either higher or lower drainage volumes and profits. One advantage of the pressurized irrigation systems is that they can be managed to obtain maximum yields and yet produce low drainage volumes.
In conclusion, the economic advantages of a given irrigation system depend on an array of factors. Variations in farm management costs associated with a given irrigation system must be considered in addition to initial capital investment costs. Furthermore, shifts in yield and drainage volumes under optimal management for different irrigation systems can provide additional costs or benefits associated with a given irrigation system. Imposition of costs on drainage water could induce a significant shift in profitability associated with a given irrigation system.
1228 92 - 11/49
USA, Mexico, arid regions, semiarid regions, field trials, crop production, microcatchments, desert-strip-farming systems, rainfed production
[Ukrainian] [English] [Russian]