HDR Engineering Inc 7/9/2019 - Laserfiche WebLink

FYR of the other project meetings scoped under other tasks and will not require a separate trip by HDR staff. 8.5 Deliverables 1. Chapter for CWP covering Water Rights and Source Reliability. Task 9 Water Yield Analysis 9.1 Objective For the 2007 CWP HDR updated the 2000 yield analysis for Spada Reservoir and the Jackson Hydropower Project. Three operational scenarios were modeled in combination with an "optimistic" and a"pessimistic" projection of runoff representing year 2050 and 2100 conditions. Climate change data came from the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. The results of that work included the following conclusions: Climate change has the potential to negatively impact Everett's safe yield. Regardless of the Spada Reservoir system scenario or whether the forecast reflected best or worst case conditions, safe yield decreased in comparison to the baseline 2000 safe yield. Safe yield declined by between 3 and 50 percent, with the greatest climate impacts occurring under the year 2100 climate and under the scenario constrained by hydropower operations. Safe yield was adequate to meet projected demands under the worst case conditions evaluated. Objective: For the 2020 CWP update the City's 2007 water supply yield analysis by obtaining more recent available information on projected runoff from the Sultan River watershed, and combining it with previously developed models of watershed runoff and system operations. Produce revised estimates of 2050 and 2100 safe yield from the watershed. 9.2 HDR Services 1. Update the 2007 watershed yield analysis to account for changes in projections of potential climate change Impacts. Potential climate change impacts will be evaluated related to the overall long-term yield of the Spada Reservoir watershed: • HDR will work with the University of Washington Climate Impacts Group (CIG) or another subconsultant to obtain three recent and accepted projections of future Sultan River meteorological conditions. (the City anticipates discussing assignment of this activity with HDR and Snohomish PUD before proceeding). • The subconsultant will use these three meteorological datasets in the previously developed and calibrated hydrological model of Sultan watershed to develop three runoff datasets for 2050 conditions, and three runoff datasets for 2100 conditions. • HDR will provide updated future demand datasets and up to three changes to system operations to be incorporated into the previously developed Everett Yield Analysis Model Everett Comprehensive Water Plan June 12, 2019 Exhibit A—Scope of Services Page 12 of 30