Sensitivity Indicator for Pressurized Irrigation Distribution Systems

Providing adequate pressure at the hydrant is an issue of great importance in the operation of pressurized irrigation distribution systems (PIDS). The hydraulic performance of these systems can be quantified by selected performance indicators to describe the performance of an irrigation system with regard to the objectives set for that system. Several indicators have been developed and used so far for the performance analysis of pressurized irrigation systems. However, none of them provides a comprehensive definition of the sensitivity of operating hydrants to the variation in the upstream discharge. The objective of this study is to develop an indicator that can quantify the sensitivity of a hydrant to the changes occurring upstream of an irrigation system. A new definition of the indicator is proposed, by considering the changes in the hydrant reliability to the changes in the upstream discharge. In other words, the sensitivity of a hydrant is simulated on the basis of the variation of its reliability to satisfy the required pressure for adequate on-farm service. This concept was applied to a case study in Italy and it showed the importance of the sensitivity indicator as defined herein in the decision-making process for proper operation of pressurized irrigation systems.