Item 3 - Preliminary WAVE Results — original pdf

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Water Forward WAVE evaluation Water Forward Task Force Meeting June 2024 Our analysis identifies candidate 50-year portfolios of supply and demand WMS UNCERTAINTIES Future Hydrologic Sequences Regional Supply Scenarios Future Water Demand Forecasts WAM WAM Needs Assessment Projected water demands and supplies Mini-WAM Model Water balance model of AW system WMS Optimization System Performance MAXIMIZES Cost MINIMIZES 50-Year Candidate WMS Portfolios INPUTS MODELING OUTPUTS Candidate portfolios are built from an optimization of nearly 2M combinations of WMS WMS Description ASR BGD IPRLBL OCR OCR+ Decker AddLCRA Additional Supply from LCRA, regional Colorado River partnerships, and/or water rights optimization Aquifer Storage and Recovery Brackish Groundwater Desalination Indirect Potable Reuse through Lady Bird Lake with local Inflows New Off Channel Reservoir, Colorado River water New Off Channel Reservoir, Colorado River and reclaimed water Off-channel reservoir supplied by Colorado River water (Decker Lake) Seawater Desalination Direct Potable Reuse from Wastewater Treatment Plant Interbasin Transfer (surface water) Importation of conventional groundwater CR - Current Ordinance, DCR - Phase 1, OR - Current Ordinance CR - Larger System, DCR - Phase 1, OR - Smaller Building Threshold CR - Larger System, DCR - Phase 1, OR - Adjusting Benchmarks SWD DPR IBT GW DR1 DR2 DR3 DR4 DR5 DR6 DR7 CR - Larger Connection Area, DCR - Phase 1, OR - Smaller Building Threshold CR - Larger Connection Area, DCR - Phase 1, OR - Adjusting Benchmarks CR - Larger System, Larger Connection Area, DCR - Phase 1, OR - Smaller Building Threshold, Adjusting Benchmarks CR - Larger System, Larger Connection Area, DCR - Phase 1, 2, OR - Smaller Building Threshold, Adjusting Benchmarks Individual WMS can be organized into specific pathways over time Can start with DR1 and continue indefinitely DR1 Time (2030 to 2080) Individual WMS can be organized into specific pathways over time Or, can start with DR1 and then jump to DR2 at some point in the future DR1 DR2 Time (2030 to 2080) Individual WMS can be organized into specific pathways over time Or, can start with DR1, then jump to DR2, and finally to DR7 DR1 DR2 DR7 Time (2030 to 2080) Individual WMS can be organized into specific pathways over time Pathways map shows full set of possible Demand Reduction Pathways DR1 DR2 DR3 DR4 DR5 DR6 DR7 Time (2030 to 2080) Rhodium selects among possible combinations to build a set of equally-optimal candidate portfolios For each candidate portfolio: 1. Portfolio configured in mini-WAM 2. Portfolio tested under 36, 30-year futures 3. Portfolio evaluated on: • Resiliency • Reliability • Vulnerability • Cost Front of optimized solutions: no objective can be improved without sacrificing another objective t s o C : 2 e v i t c e b O j Ideal solution: cheap & reliable Rhodium selects equally-optimal portfolios Those that offer the “best” performance and cost, or those that can’t do better on one metric without sacrificing another. Objective 1: Performance metrics Candidate portfolios will be further evaluated by Austin Water Front of optimized solutions: no objective can be improved without sacrificing another objective t s o C : 2 e v i t c e b O j Ideal solution: cheap & reliable Objective 1: Performance metrics e r o c S o i l o f t r o P 1 o i l o f t r o P 2 o i l o f t r o P 3 o i l o f t r o P 4 o i l o f t r o P Of nearly 2M options, the optimization identified ~550 candidate portfolios for 2080 Resilience of system without WMS We can look at a few candidate portfolios on this curve Portfolio 3 10 WMS (460,000 AFY) Portfolio 2 7 WMS (340,000 AFY) Portfolio 1 4 WMS (200,000 AFY) Tradeoffs between optimization metrics will be assessed by Austin Water as a part of a fuller multi- criteria analysis Portfolio Number of WMS 4 Total Yield (AFY) 200,000 7 10 340,000 460,000 1 2 3 Reliability Resiliency Vulnerability Cost* 92 97 100 66 88 90 97 99 100 $1.4B $6.2B 4.3 times as much as Portfolio 1 $12.8B 8.8 times as much as Portfolio 1 Implementing more adaptive strategies by 2080 could soften the cost and performance tradeoff *Total portfolio costs are estimated for all WMS as the sum of O&M and capital costs over a 30-year period