Resilience of regional water supply systems

Resilience is defined as the ability of a system to limit the impact of a disturbance and to return to its full functionality after a disturbance. Resilience is becoming a distinct topic in several different fields of research, but it has yet to be implemented in water resources and in particular to regional water supply systems (RWSS). According to Bruneau et al. (2003), resilience is a function of the loss of system functionality and the duration of a failure event. The loss of functionality is related to the redundancy and robustness of the system while the recovery time is a function of system resourcefulness in developing and the rapidity of responses. As failure likelihoods and recovery times in RWSS are difficult to assess, this paper focuses on redundancy and robustness and the internal dynamics of the underlying RWSS while it is impaired. To that end, a linear programming (LP) flow allocation model is employed. The model represents a portion of the Tucson metropolitan area and was designed to be adaptable so that it can be applied to a general RWSS. The model determines the optimal flow allocation within a RWSS that minimizes cost. Greenhouse gas production and energy consumption are computed as secondary outputs. Various infrastructures were modeled by adding satellite waste water treatment plants (decentralization) in different locations to compare with a centralized system. RWSS resilience is measured as the volume of water that is not delivered to users (shortages) for several infrastructure failure scenarios. Results were compared between various system configurations to identify the most resilient system structure and critical infrastructure components that affect system resilience.