Extending the Decision-Making Lead time of Municipal Water System Management through Teleconnections and Novel Methods for Estimating Supply and Demand

With populations increasing in arid regions and greater uncertainty in the timing and volume of surface water supplies, western water system management requires estimates of system performance with sufficient lead time to identify and mitigate potential vulnerabilities. Given the dependence of these systems on winter snowpack and the resulting timing of surface water availability contrasting to that of peak municipal water demand, there is a need to deliver earlier estimates of system performance to increase the lead time for decision-making. Addressing this need, we assemble an interdisciplinary team of climatologists, hydrologists, and engineers to develop a long to short-term water systems operations workflow that provides operators with performance estimates up to a 24-month lead time. We apply this workflow as part of a collaborative partnership with Salt Lake City Department of Public Utilities, where we develop a Probabilistic Supply Estimator informing the probability of supply based on observed streamflow deficits out to two years and use the correlated state of the hydroclimate to estimate demand; leverage teleconnections with global climate signals to estimate the precipitation anomaly for use in models forecasting surface water yield and demand for the proceeding ten months; use NOAA seasonal climate outlooks to refine estimates of supply and demand out to 6 months; and integrate the National Water Model for 30-day estimates of supply to support short-term analysis. For each lead time, we use the estimates of supply and demand to drive a water systems model that provides a range of likely reservoir levels, volume of groundwater withdrawals, and volume of out-of-district water needs. We determine potential system vulnerabilities by evaluating these projections to critical performant thresholds, providing management with an extended period to assess preemptively and develop mitigation strategies to a range of hydroclimate phenomena to enhance water system-climate resilience.