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Optimized Flood Control in the Columbia River Basin for a Global Warming Scenario Se-Yeun Lee1, Alan F. Hamlet 2,1 Carolyn J. Fitzgerald3 Stephen J. Burges1 Dennis P. Lettenmaier1, 2 1 Dept. of Civil and Env. Engineering, UW 2 CSES Climate Impacts Group, UW 3 U.S. Army Corps of Engineers, Seattle District Motivation Trends in April 1 Snowpack from 1950-1997 Red - Negative Trend Blue – Positive Trend Mote P.W.,Hamlet A.F., Clark M.P., Lettenmaier D.P., 2005, Declining mountain snowpack in western North America, BAMS, 86 (1): 39-49 As the West warms, spring flows rise and summer flows drop Stewart IT, Cayan DR, Dettinger MD, 2005: Changes toward earlier streamflow timing across western North America, J. Climate, 18 (8): 1136-1155 Red - Negative Trend Blue – Positive Trend Hydrologic Impacts of Global Warming on Snowmelt Dominant Rivers 1200 20th Century Increased Winter Flows Earlier Melt Earlier Spring Peak Flow Inflow (KAF) Reduced Spring Snowpack Climate Change 800 400 Decreased Summer Flow 0 Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Month 8000 7000 6000 5000 4000 3000 2000 1000 0 Sep 20000 15000 Sep Aug Jul Jun May Apr Mar Feb Jan Dec Nov 10000 Oct Jul Full 25000 Storage : Current Climate Aug Jun Apr May Mar Feb Jan Dec Oct 30000 Nov Reservoir Inflow Flood Control vs. Refill Flood Control vs. Refill Streamflow timing shifts can reduce the reliability of reservoir refill 8000 + 2.25 oC 6000 5000 4000 3000 30000 Full 2000 1000 25000 : Current Climate Storage Sep Jul Aug Jun Apr May Mar Jan Feb Dec Oct 0 Nov 20000 : + 2.25 oC No adaption 15000 Sep Aug Jul Jun May Apr Mar Feb Jan Dec Nov 10000 Oct Reservoir Inflow 7000 Flood Control vs. Refill Streamflow timing shifts can reduce the reliability of reservoir refill 8000 7000 + 2.25 oC 5000 4000 30000 3000 Full 2000 1000 : Current Climate Storage Aug 25000 Sep Jul Jun Apr May Mar Jan Feb Dec Oct 0 Nov 20000 : + 2.25 oC No adaption 15000 Sep Aug Jul Jun May Apr Mar Feb Jan Dec 10000 Nov : + 2.25 oC plus adaption Oct Reservoir Inflow 6000 Objective: Develop Systems Engineering Procedures for Rebalancing Flood Control and Reservoir Refill Flood Control Refill Test Case: The Columbia River Basin Multi-objective Reservoir System Flood Control Hydropower Instream Flow Water Supply Recreation Navigation Major U.S. Flood Control Checkpoints Bonners Ferry Columbia Falls The Dalles Methods Optimization –Simulation Models Developing Optimized Flood Control Curves Testing and refining Proposed Rule Curves HEC-PRM (Hydrologic Engineering Center’s Prescriptive Model) Optimization model developed by the US Army Corps of Engineers Penalty functions are used to constrain the Columbia River basin system operation Flood control penalties Storage penalties ColSim (Columbia Simulation Model) Flood control Hydropower Irrigation Instream flow Navigation Recreation Calibration Strategy Select Objective Function Parameters Generate Optimized Flood Rule Curves Adjust AdjustParameters Parameters Evaluate Flood and Refill Statistics Using Simulation Calibration Results Calibration Results (Refill) Refill Probability (unit :%) Dam Arrow 20th Century Flow Current FC 20th Century Flow Optimized FC 8.1 18.6 Brownlee 36.0 36.0 Duncan 98.8 98.8 9.3 14.0 Grand Coulee 33.7 37.2 Hungry Horse 29.1 31.4 Libby 54.7 53.5 Mica 66.3 67.4 Dworshak Calibration Results (Flood Control) 60 Bonners Ferry 50 Peak flow at Columbia Falls (kcfs) Peak flow at Bonners Ferry (kcfs) 60 20th Cent_CurFC 20th Cent_HecFC 40 30 20 Columbia Falls 50 20th Cent_CurFC 20th Cent_HecFC 40 30 20 10 10 -2 -1 0 1 2 3 4 -2 5 -1 0 1 2 Y Y 600 Red - Current FC Blue - Optimized FC Peak flow at The Dalles (kcfs) The Dalles 500 20th Cent_CurFC 20th Cent_HecFC 400 300 200 100 -2 -1 0 1 2 Y 3 4 5 3 4 5 VIC Hydrologic Model (Variable Infiltration Capacity Hydrologic Model) Macroscale Hydrologic Model developed by University of Washington Climate Change Scenario Remove historic monthly temperature trends from the daily time step forcing data Increase the temperatures by 2 oC (annual average) in a seasonal pattern derived from several GCM simulations Observed precipitation Monthly Simulated Reservoir Inflows Dworshak 1200 20th Century Inflow (KAF) Climate Change Scenario 800 400 0 Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Month Libby 2,500 : Current Climate : Climate Change Scenario Inflow (KAF) 2,000 20th Century Climate Change Scenario 1,500 1,000 500 0 Oct Nov Dec Jan Feb Mar Apr Month May Jun Jul Aug Sep Creating New Flood Control Rule Curves Current Flood Rule Curves Flood Control Rule Curves are selected by Apr-Jul Flow Volume Dworshak Flood Control Curves 3700 Storage (KAF) 3300 2900 2500 2100 1700 1300 Nov Dec Jan Feb Mar Month Apr May Jun New Flood Rule Curves Find Flow Volume Ranges for each category with an equal number of events Number of samples DW Apr-Jul Flow Volume FC 1 18 < 1.8 MAF FC 2 17 < 2.6 MAF FC 3 17 < 2.9 MAF FC 4 17 < 3.2 MAF FC 5 17 >=3.2 MAF New Flood Rule Curves Find Flow Volume Ranges for each category with an equal number of events Use 80th percentile values for each categories as a Flood Rule Curve DW Apr-Jul Flow Volume FC 1 18 < 1.8 MAF FC 2 17 < 2.6 MAF FC 3 17 < 2.9 MAF FC 4 17 < 3.2 MAF 4,000 3,500 Storage (KAF) Number of samples 3,000 2,500 2,000 FC 4 1,500 1,000 Oct FC 5 17 >=3.2 MAF Nov Dec Jan Feb Mar Apr May Jun Jul Months : 17 ensemble traces : 80th percentile of ensembles Optimization Model Results Current Climate vs Climate Change Scenario Dworshak storage (Dworshak Apr-Jul flow volume >2.40 MAF) a) 20th Century Climate Mar 4,000 3,000 2,500 2,000 b) Climate Change Scenario 1,500 1,000 Oct Nov Dec Jan Feb Mar Apr May Jun Jul 4,000 Months Feb 3,500 : Ensemble traces : 80th percentile of ensembles Storage (KAF) Storage (KAF) 3,500 3,000 2,500 2,000 1,500 1,000 Oct Nov Dec Jan Feb Mar Apr May Jun Months Jul Libby storage (Libby Apr-Aug flow volume >5.5 MAF) a) 20th Century Climate Apr 6,000 Storage (KAF) 5,000 4,000 3,000 2,000 b) Climate Change Scenario 1,000 0 Oct Nov Dec Jan Feb Mar Apr May Jun Mar Jul 6,000 Months : Ensemble traces : 80th percentile of ensembles Storage (KAF) 5,000 4,000 3,000 2,000 1,000 0 Oct Nov Dec Jan Feb Mar Apr May Jun Months The changes in flood control rule curves are different for different projects Jul Simulation Model Results: Reservoir Storage Results Refill Probability of Libby (Libby Apr-Aug flow volume>5.5 MAF) 20th Century Flow CC Scenario Flow CC Scenario Flow Current FC Current FC HEC-PRM FC June 54 39 71 July 61 42 61 Full Storage (KAF) 6000 5000 4000 3000 2000 1000 CC_Scen_CurFC CC_Scen_HecFC 0 Oct Nov Dec Jan Feb Mar Apr May Jun Jul Month Refill Probability of Dworshak (Dworshak Apr-Jul flow volume >2.40 MAF) 20th Century Flow CC Scenario Flow Current FC Current FC CC Scenario Flow HEC-PRM FC May 0 0 25 June 49 19 44 July 14 0 0 Storage (KAF) 3500 3000 CC_Scen_CurFC CC_Scen_HecFC 2500 2000 1500 Oct Nov Dec Jan Feb Mar Apr May Jun Month Jul Changes in Reservoir Storage Total System Wide July Storage (KAF) CC_Scen _HecFC 55000 50000 45000 : The Dalles Apr-Aug < 68 MAF : 68 <= The Dalles Apr-Aug <100 MAF : The Dalles Apr-Aug >=100 MAF 40000 40000 45000 50000 55000 CC_Scen _CurFC Greatest Improvement occurs in Mid flow years ( ) Simulation Model Results: Flood-Frequency Results Flood-Frequency Curves for Bonners Ferry Peak flow at Bonners Ferry (kcfs) 60 50 20th_Cent_CurFC CC_Scen_CurFC CC_Scen_HecFC 40 30 20 10 -2 -1 0 1 2 Y 3 4 5 Flood-Frequency Curves for Columbia Falls Peak flow at Columbia Falls (kcfs) 50 40 20th_Cent_CurFC CC_Scen_CurFC CC_Scen_HecFC 30 20 10 0 -2 -1 0 1 2 Y 3 4 5 Flood-Frequency Curves for The Dalles Peak flow at The Dalles (kcfs) 600 500 20th_Cent_CurFC CC_Scen_CurFC CC_Scen_HecFC 400 300 200 100 -2 -1 0 1 2 Y 3 4 5 Conclusions Optimization studies provide an objective method for rebalancing flood control and refill objectives in complex reservoir systems in response to hydrologic changes. The changes in flood control rule curves are different for different projects, corresponding to different changes in flow volume and timing associated with warming in each sub basin. Conclusions Optimized flood control rule curves show reduced flood evacuation and earlier refill timing; up to one month earlier for a climate change scenario, compared with 20th century climate. For the climate change scenario, optimized flood rule curves increase reservoir refill as well as the system storage in moderate and high flow years, while providing comparable levels of local and system-wide flood protection in comparison to the current flood control rule curves. Future Work Extension and refinement of our methods using daily time step optimization and simulation models is needed to evaluate the robustness of these techniques in more detailed planning studies. Questions?