The use of resilience metrics to support decision making in drinking water systems.

Abstract

Performance assessment is essential for effectively managing drinking water systems. It allows to understand the system's behaviour, identify critical components and subsystems, and help with the decision analysis of measures to improve economic, infrastructural and water and energy resources. The current paper proposes an updated methodology for diagnosing drinking water networks, considering different perspectives: water and energy efficiency, infrastructural sustainability, and the quality of service provided, including resilience and redundancy concepts. Several performance indicators and indexes, including Resilience index and Entropy, are recommended to describe each perspective. The methodology is applied to a real-life network, and the attained results are discussed. The status quo situation for the network area is assessed, and the main problems are identified (i.e., high friction losses, inefficient pump operation, old pump equipment). Different improvement solutions are considered (e.g., pipe replacement with higher diameter, pump operation improvement, pump replacement). These interventions are considered individually or combined. Using the resilience-based perspective with other performance assessment criteria has provided a broader assessment. The resilience index has proven sensitive to the different alternatives, endorsing the system's efficiency. Smaller values of the resilience index indicate that a small amount of energy in excess is available as surplus energy in the consumption nodes, being dissipated, either as pumping inefficiencies, water losses, or friction and singular head losses. The Entropy metric is sensitive to the network layout and is helpful in alternatives that consider flow path alterations to prevent the impact of pipe failure. The best improvement alternative achieves a considerable enhancement in energy efficiency, maintains a good quality of service, improves the system's infrastructural sustainability, and corresponds to the highest resilience index value.