The Impacts of Climate Change on Portland s Water Supply Richard Palmer and Margaret Hahn University of Washington Department of Civil and Environmental Engineering Joe Dvorak, Dennis Kessler, Azad Mohammadi Portland Bureau of Water Works
Bull Run Watershed Area
Talk Overview Summary Introduction Watershed Hydrology Models Impacts on Watershed Impacts on Demands Impacts on System Performance Conclusions
Summary Temperatures will increase by 2 C by 2040, with higher temperatures in the summer Precipitation will increase in the winter and decrease in the summer. These changes will increase winter streamflows and decrease summer flows. Climate change will decrease system inflows by about 1.3 billion gallons during the drawdown cycle and increase water demands by 1.5 billion gallons. By 2040, increase in demand, without climate change could be 5.5 billion gallons
Evaluation of Climate Change Meteorological data Climate Shift Hydrology model Calibration Impacts Evaluation Precip and temp Downscaled GCM DHSVM Historic vs Simulated System Simulation model
Watershed Hydrology Bull Run has x square miles Average elevation Average productivity Average Rainfall Average snowpack
Hydrology Highlights Bull Run is a rainfall driven watershed
800 Average Monthly Values for Flow and Precipitation Bull Run Watershed Bull Run Flows near Multnomah Falls Bull Run Precipitation at Headworks 35 700 30 flow, cfs 600 500 400 300 200 100 25 20 15 10 5 precipitation, cm 0 Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep 0
7 Average Monthly Snow Water Equivalent (1979-1999) North Fork Bull Run Snotel Site # 22D02S Snow Water Equivalent, (inches) 6 5 4 3 2 1 0 Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep
Hydrology Highlights Snow Melt comes of typically before July
Combined Bull Run Reservoir Level 1952 Hydrology with 2000 System Configuration 20,000 Top of conservation pool Dam1 and 2 Combined Reservoir Level Bottom Conservation Pool 18,000 16,000 14,000 Million Gallons 12,000 10,000 8,000 6,000 4,000 2,000 0 Jan-52 Mar-52 May-52 Jul-52 Sep-52 Nov-52 Jan-53
Hydrology Highlights There is very little water needed to fill Bill Run Reservoirs in the spring
General Approach to Modeling Climate Change Three models used Figure 19 Some models we built, some we used. GCMs DHSVM STM
Describe each GCMs
DHSVM Figure 20 How well does the hydrology model capture the system. Figures 21 and 22 Why is it not better? Data Groundwater
STM What is the STM Figures 25 and 26
What are the basics climate signals? Figures 29, 30, 31 and 32.
4 3.5 3 Temperature Change for Climate Change Scenarios 2020 Climate Change 2040 Climate Change Degrees C 2.5 2 1.5 1 0.5 0 Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep
1.2 1.15 Precipitation Fraction for Climate Change Scenarios 2020 Climate Change 2040 Climate Change Fraction Precipitation 1.1 1.05 1 0.95 0.9 0.85 0.8 Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep
35 Observed and Climate Change Average Monthly Precipitation at Headworks for Bull Run observed (1961-1990) 2020 Climate Change Average 2040 Climate Change Average Monthly Precipitation, cm 30 25 20 15 10 5 0 Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep
25 Observed and Climate Change Average Monthly Temperature at Headworks for Bull Run observed (1961-1990) 2020 Climate Change Average 2040 Climate Change Average Temperature, degree C 20 15 10 5 0 Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep
DHSVM Distributed Hydrology-Soil-Vegetation Model
Hydrologic Characteristics of PNW Rivers Normalized Streamflow 3.0 2.5 2.0 1.5 1.0 0.5 Snow Dominated Transient Snow Rain Dominated 0.0 10 11 12 1 2 3 4 5 6 7 8 9 Month
800 Average Monthly Values for Flow and Precipitation Bull Run Watershed Bull Run Flows near Multnomah Falls Bull Run Precipitation at Headworks 35 700 30 flow, cfs 600 500 400 300 200 100 25 20 15 10 5 precipitation, cm 0 Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep 0
1600 Annual Average Bull Run Inflows 1950-1999 Observed Average Annual Flows DHSVM 1400 1200 Inflows, cfs 1000 800 600 400 200 0 Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep
1800 1600 Annual Average Bull Run Inflows 1950-1999 Current Climate Average Annual Inflow- BR Average 2020 Climate Change Average 2040 Climate Change 1400 1200 Inflows, cfs 1000 800 600 400 200 0 Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep
Jun-66 Jul-66 Aug-66 Sep-66 Oct-66 May-66 4000 3500 3000 2500 2000 1500 1000 500 0 Bull Run River Flows into Dam 1 DHSVM 2020 Climate Change Average 2040 Climate Change Average Oct-65 Nov-65 Dec-65 Jan-66 Feb-66 Mar-66 Apr-66 cfs
Supply and Transmission Model Simulation model of Portland water supply system Inputs are streamflow and demand forecasts Considers: future demands, policies, supplies and infrastructures Evaluates system and scenario performance Uses daily time step Developed in Stella
MainMenu
STMdrawdown
Analysis Scenario Status Quo No infrastructure or management changes to the system for the next 50 years Examine both climate and demand forecasts Analysis scenario, not a planning scenario Look at Annual Minimum Storage for period of record
Annual Minimum Storage less Shortfalls Combined Bull Run Reservoirs Dam 1 and Dam 2 2000 System Configuration and 2000 demands 16000 Current Climate Average 2020 Climate Average 2040 Climate 14000 12000 million gallons 10000 8000 6000 4000 2000 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995
Annual Minimum Storage less Shortfalls Combined Bull Run Reservoirs Dam 1 and Dam 2 2000 System Configuration 16000 Current Climate - 2000 Demand Current Climate - 2020 Demand Current Climate - 2050 Demand 14000 million gallons 12000 10000 8000 6000 4000 2000 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995
Annual Minimum Storage less Shortfalls Combined Bull Run Reservoirs Dam 1 and Dam 2 16000 Current Climate/ 2000 Demand 2020 Climate Change / 2020 Demand 2040 Climate Change / 2050 Demand 14000 12000 million gallons 10000 8000 6000 4000 2000 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995
Combined Bull Run River Reservoir Volume - 1982 Top Conservation Pool Reservoir Volume - 2000 Demand / 2000 Climate Reservoir Volume - 2000 Demand / 2040 Climate Reservoir Volume - 2050 Demand / 2000 Climate Reservoir Volume - 2050 Demand / 2040 Climate Bottom of Conservation Pool River Excess Million Gallons 20,000 18,000 16,000 14,000 12,000 10,000 8,000 6,000 4,000 2,000 0 Jan-82 Mar-82 May-82 Jul-82 Sep-82 Nov-82 Jan-83
Planning Scenarios GW and Improve Infrastructure Raise Dam 1 Treat dead storage in Dam 2 Reliance on GW Conservation and Improve Infrastructure Raise Dam 1 Treat dead storage in Dam 2 Full Conservation Measures Build 3 rd Dam in Watershed
Drawdown Length in Days 1982 Hydrology for System Configurations GW, Cons and Dam 3 Current Climate and Climate Change 250 Current Climate Climate Change 200 150 Days 100 50 0 GW 2000 GW 2020 GW 2050 Cons 2000 Cons 2020 Cons 2050 Dam 3 2000 Dam 3 2020 Dam 3 2000 System Configuration and Demand Year
Annual Storage Used for 1982 Hydrology for System Configurations GW, Cons and Dam 3 Current Climate and Climate Change 16,000 Current Climate Climate Change 14,000 12,000 Million Gallons 10,000 8,000 6,000 4,000 2,000 0 GW 2000 GW 2020 GW 2050 Cons 2000 Cons 2020 Cons 2050 Dam 3 2000 Dam 3 2020 Dam 3 2000 System Configuration and Demand Year
Annual Minimum Storage for 1982 Hydrology for System Configurations GW, Cons and Dam 3 Current Climate and Climate Change 30,000 Current Climate Climate Change 25,000 Million Gallons 20,000 15,000 10,000 5,000 0 GW 2000 GW 2020 GW 2050 Cons 2000 Cons 2020 Cons 2050 Dam 3 2000 Dam 3 2020 Dam 3 2000 System Configuration and Demand Year
Groundwater Pumped during Drawdown for 1982 Hydrology for System Configurations GW and Cons Current Climate and Climate Change 4,500 Current Climate Climate Change 4,000 3,500 Million Gallons 3,000 2,500 2,000 1,500 1,000 500 0 GW 2000 GW 2020 GW 2050 Cons 2000 Cons 2020 Cons 2050 System Configuration and Demand Year
Planning Scenario Conclusions Planning scenarios remain reliable under climate change. For all planning scenarios Drawdown start date is sooner Length of drawdown increases Groundwater use reduces impacts of climate change on surface system