A comprehensive performance assessment system for diagnosis and decision-support to improve water and energy efficiency and its demonstration in Portuguese collective irrigation systems

Abstract

In regions with a strong seasonal or interannual asymmetry in the distribution of precipitation and higher frequency of droughts, collective irrigation systems are vital infrastructures for agricultural activity. Although operating for decades, several systems have ageing infrastructures, with relevant water losses and pumping energy inefficiencies. Consequently, the systems are not adequately designed or operated to meet current and future water demand. Therefore, rehabilitation to improve water and energy efficiency while ensuring infrastructure, economic sustainability and service quality is crucial. In this sense, comprehensive approaches using performance assessment to support the planning process or benchmarking between water users associations play an essential role in improving efficiency in collective irrigation systems. However, few methodologies assess interdependencies between water losses, energy efficiency, infrastructure condition, service quality, economic and operational dimensions. Additionally, these approaches rarely were applied to the different stages of the planning process (diagnosis, planning, monitoring, and reviewing the impact of measures) and to different types of collective irrigation systems (gravity, pressurised, combined) for comparative analysis. This paper presents a comprehensive performance assessment system (PAS) for diagnosis and decision support about measures to improve water and energy efficiency in collective irrigation systems. Afterwards, the PAS is applied for diagnosis and prioritisation of alternatives to enhance the efficiency of a gravity system. The results indicate significant water losses due to the canal and intermediate reservoirs discharges and leakage in canals and low-pressure pipes, related to network ageing and insufficient flow monitoring and control for the gravity system. Ranking allowed identifying the gravity network area with high priority of intervention due to poor performance in non-revenue water, water losses due to discharges, energy efficiency of pumping stations and system energy in excess. Several alternatives were studied for this network area, and infrastructural solutions involving canal rehabilitation and water discharge control significantly impact global performance improvement besides the substantial investment associated. Subsequently, the PAS is used for comparing gravity and pressurised systems. In opposition to gravity, the pressurised system, with efficient use of water resources, presents a poor performance in pumping energy efficiency. Furthermore, the significant energy costs indicate the importance of energy improvement measures for the pressurised system. Besides assessing water and energy efficiency, the novel PAS may help managers and policymakers identify every system's best practices and weak points.