Reservoir Operations for Climate Change Adaptation in the Washington, D.C. Metropolitan Area

Transcription

1 Reservoir Operations for Climate Change Adaptation in the Washington, D.C. Metropolitan Area M. Wiley Rivera, S. Nebiker, C. Schultz, B. Wright, G. Day, D. Sheer, B. Stanford 14 AWRA Annual Water Resources Conference

2 Overall Project Goals Demonstrate the potential value of dynamic reservoir operations (DRO) in improving system reliability, resilience, and performance under challenging climate conditions; Provide utilities with practical guidance to decide if and how to implement DRO. 2

3 Dynamic Reservoir Operations Dynamic operations are more flexible and capitalize on more information than static ops: Current reservoir storage Groundwater levels Water quality conditions Time of year Inflows Demand Antecedent conditions (e.g. first, second or third year of a drought) Forecasts - long and short term (hydrology, meteorology, demand, economic, etc.) 3 Climatic conditions (e.g. El Niño) Environmental conditions Fish spawning Instream flow requirements Flow requirements for aquatic species Antecedent flow Water temperature Electricity prices (for generation) Water Treatment and pumping costs

4 Utility Participants New York City WSSC/ Fairfax/ ICPRB City of Calgary Existing Tools Yes Yes Yes Population Served Major Drainage Basins Interbasin Transfers SEQ Grid Manager Under development Kansas Water Office Yes Newport News Waterworks ~9 million ~5 million ~3, ~2.5 million ~1 million ~4, Delaware and Hudson Potomac Bow Multiple Kansas Yes No No Yes, for treated water No Yes Chickahominy No Water Quality Issues Turbidity/ organics Watershed development Nutrients Watershed Development TDS Watershed development Regulatory Context Active Climate Change Planning Existing Dynamic Operations 4 Interstate Compact/ Filtration Avoidance Determination Contractual water sharing Water licenses State allocation of water rights Water Assurance District State regulations Yes Yes Yes Yes Yes Yes Yes Yes No No Yes Yes Geography Northeast Mid Atlantic Mountain West Tropical Great Plains Mid Atlantic

5 Washington Metro Region Demand and Supply 5

6 Framework for WMA s Operations Negotiated Using Drought Exercise 6

7 Washington Metro Region Operations Primary Operational Issues Shifting between Potomac and local sources Efficient conjunctive use of Jennings Randolph and Little Seneca 7

8 Creating a Starting Point for Operations Development See WaterRF report Washington, D.C. Metro Region already has DRO 8

9 Step 1: Develop Performance Measures & Evaluation Tools % Usable Storage Minimum Storage Each Simulated Year in Potomac Reservoirs a) b) Alternative 1 Alternative % of Years Percent of Simulated Years that Patuxent Reservoir Refills (9% full) on June Alternative Number of Days c) Number of Days with Pump Switching, <3 MGD Flow Days Year of Simulation Alternative 1 Alternative d) % of Years Percent of Years with Water Use Restrictions (Highest Level for the Year Shown) Voluntary Mandatory Emergency Alternative

10 Water Management Model OASIS Used to Simulate System Jennings Randolph Reservoir Westernport Demand Savage Reservoir North Branch at Luke 14 Little Seneca Reservoir Patuxent Reservoir Broad Run WW Return 5 Misc.Consumptive Use Little Seneca WWTP Return WSSC Demand 136 Pat MinRelease Node FCWA Potomac Intake Rockville Demand 18 WSSC Intake UOSA WW Return Rockville Intake FCWA West (Potomac) Demand Aqueduct Demand 163 Great Falls Intake FCWA East (Occoquan) Demand Water budgets Reservoir operations Inflows and withdrawals 125 Little Falls Intake 2 Occoquan Reservoir Flow Downstream of Little Falls 127 Production loss terminal

11 Step 2: Develop Climate Change Inflow Scenarios 11 Delta change method using Climate Change Decision Support System (CCDSS) 112 Bias Corrected and Statistically Downscaled (BCSD) GCM datasets NWS Middle Atlantic River Forecast Center s (MARFC) hydrologic model used for Potomac (with bias correction)

12 O f C OOP93621 TMEAN Step 3: Evaluate System Reliability under Different Climate Change Scenarios and Recommend Changes to Operating Rules Historical temperature and precipitation records Delta Transform Ensemble of 112 climate-adjusted temp & precip traces Hydrologic Model Ensemble of 112 inflow and evaporation traces Water Management Model Performance Measure Tool 12 Ensemble of 112 flow and reservoir stage traces Decision Support Displays

13 Working with Select Traces Is Part of the Process Developing operations is an art as well as a science Following your nose is part of the process This is difficult with an ensemble vs Usable Storage (%) Jennings Randolph Water Supply Account Storage Optimization techniques are helpful tools 13 but not a substitute for human ingenuity Year

14 An Approach to Operations Development with Ensembles Are there operational responses that address the MOST EXTREME climate scenario(s)? Do these operations perform well under historical hydrology, the ensemble of climateadjusted streamflows, and synthetic hydrology? Work with less extreme traces and consider structural responses Consider instituting operations immediately Develop climate (or other) thresholds that would suggest implementing operations; work with less extreme traces; and/or consider structural responses 14

15 An Approach to Operations Development with Ensembles Inmcm3_ srsae1b Are there operational responses that address the MOST EXTREME climate scenario(s)? 15 Do these operations perform well under historical hydrology, the ensemble of climateadjusted streamflows, and synthetic hydrology? Consider instituting operations immediately Work with less extreme traces and consider structural responses Adjusted trigger levels for drought restrictions Increased demand reductions Develop climate (or other) Adjusted the existing rule ( buffer ) to thresholds that would suggest better balance drawdown in reservoirs implementing operations; work Adjusted trigger level for reducing with less extreme traces; and/or withdrawals to emergency levels consider structural responses Adjust trigger for source shifting Reduce seasonal drawdown in reservoir Reduced minimum release based on low storage level

16 An Approach to Operations Development with Ensembles Inmcm3_ srsae1b Are there operational responses that address the MOST EXTREME climate scenario(s)? 16 Do these operations perform well under historical hydrology, the ensemble of climateadjusted streamflows, and synthetic hydrology? Consider instituting operations immediately Work with less extreme traces and consider structural responses Adjusted trigger levels for drought restrictions Increased demand reductions Develop climate (or other) Adjusted the existing rule ( buffer ) to thresholds that would suggest better balance drawdown in reservoirs implementing operations; work Adjusted trigger level for reducing with less extreme traces; and/or withdrawals to emergency levels consider structural responses Adjust trigger for source shifting Reduce seasonal drawdown in reservoir Reduced minimum release based on low storage level

17 Operational Changes Prevent System Failure, But With Difficult Cutbacks Usable Storage (%) Jennings Randolph Water Supply Account Storage Year Usable Storage (%) Little Seneca Storage Year CC35 (Current Ops) CC35 (Modified Ops) CC35 (Current Ops) CC35 (Modified Ops) Usable Storage (%) Patuxent Storage (WSSC Source) Year CC35 (Current Ops) CC35 (Modified Ops) Usable Storage (%) Also emergency production levels at treatment plant Demand Reduction (%) Occoquan Storage (Fairfax Water Source) Year CC35 (Current Ops) 15 5 Demand Restrictions CC35 (Modified Ops) Year CC35 (Current Ops) CC35 (Modif ied Ops)

18 The Cutbacks are Only Triggered in the Most Extreme Hydrologic Traces 18

19 Similar Results for Low Flows at Water Treatment Plant 19

20 Conclusions Operational changes prevented system failure under the 112 climate-adjusted hydrologic traces analyzed The primary trade-off was an increase in the frequency and magnitude of predicted demand restrictions and an increase in time with low flow to treatment plant The operational response provides a cushion in the case of severe hydrologic shift while other responses are developed