Performance of water supply operations measured by reliability and marginal cost

This study develops and applies a concept of combining marginal cost and reliability in an operational water supply model. This concept can be used to gauge the performance of various water supply strategies. Traditional methods of water supply planning typically capture capital costs of new supplies but do not necessarily capture measurements of reliability and operational efficiencies. Reliability and efficiency can significantly impact performance of producing and delivering water. Rapid population growth, climate change, extended droughts, and increasing public scrutiny are all reasons why it is becoming more important for water supply planners to develop strategies that provide reliable and cost-efficient solutions to the public. Based on a concept previously developed, this study uses an approach of assessing reliability of water supply and marginal costs by incorporating both supply and demand-side management options. Risk-based reliability of the system is estimated as a function of shortages in flow rate and system storage volumes. The new approach is applied to a water supply planning model for the Washington County Water Conservancy District (District), a regional water wholesaler located in St. George, Utah. The results of this study show that increased operational efficiencies can be found while maintaining higher reliability in the system. The results also show that this approach can provide better insight into timing of large future supply acquisitions.