Columbia River Basin Water Supply and Irrigation Demand Forecast for the 2030s Jennifer C. Adam, Assistant Professor Civil and Environmental Engineering Washington State University

WSU Modeling Team Civil and Environmental Engineering / State of Washington Water Research Center Jennifer Adam, Assistant Professor Michael Barber, Professor and Director of SWWRC Kiran Chinnayakanahalli, Postdoctoral Associate Kirti Rajagopalan, PhD Student Shifa Dinesh, PhD Student Matt McDonald, MS Student Biological Systems Engineering Claudio Stöckle, Professor and Chair Roger Nelson, Research Associate Keyvan Malek, PhD Student School of Economics Michael Brady, Assistant Professor Jon Yoder, Associate Professor Tom Marsh, Professor and Director of IMPACT Center Center for Sustaining Agriculture and Natural Resources Chad Kruger, Director Georgine Yorgey, Research Associate

Background  The economic, ecologic, and cultural well being of Washington's Columbia River Basin depends on water  Irrigation largest water user  Economic value of agriculture (5 billion $ in WA)  Water resources sensitive to climate change  Better understanding of future range in supply and demand needed to guide investment decisions

Predicted Climate Changes  Temperature  Annual temperature increase (0.2 to 1.0°F / decade)  Summer increases are greater than other seasons  Precipitation  Annual precipitation: less agreement among Global Climate Models (small on average: +1 to +2%)  Summer precipitation decreases; other seasons increase  Net Result: shifting of water availability away from summer season of peak irrigation water demand

Goals  To project 2030s water supply and (agricultural and municipal) demand in the Columbia River Basin  WA Dep. of Ecology Report to State Legislature (November, 2011)

Linked WSU Study Components 1. Biophysical modeling of historical and future water supply and irrigation demand 2. Municipal Demand Forecast 3. Hydropower Review 4. Regional survey of Columbia River Basin water managers 5. Economic analyses of domestic and international factors driving agricultural production 6. Outreach

Unique Aspects of Approach: *Integration of Surface Hydrology and Cropping Systems *Incorporation of Water Management (Reservoirs and Curtailment of Interruptible Irrigation Rights) *Integration with Economic Modeling Modeling Framework

Models Used VIC Hydrology Liang et al, 1994 CropSyst Cropping Systems Stockle and Nelson 1994

VIC-CropSyst Model 1. Weather (D) 2. Soil Soil layer depths Soil water content 3. Water flux (D) Infiltrated water 4. Crop type Irrigation water = Crop Water Demand /irrigation efficiency Sow date Crop interception capacity Crop phenology Crop uptake (D) Water stress (D) Current biomass (D) Crop Water demand (D) Harvest day Crop Yield VICCropSyst D – communicated daily

Crops Modeled  Winter Wheat  Spring Wheat  Alfalfa  Barley  Potato  Corn  Corn, Sweet  Pasture  Apple  Cherry  Lentil  Mint  Hops  Grape, Juice  Grape, Wine  Pea, Green  Pea, Dry  Sugarbeet  Canola  Onions  Asparagus  Carrots  Squash  Garlic  Spinach Generic Vegetables  Grape, Juice  Grass hay  Bluegrass  Hay  Rye grass  Oats  Bean, green  Rye  Barley  Bean, dry  Bean, green Other Pastures Lentil/Wheat type  Caneberry  Blueberry  Cranberry  Pear  Peaches Berries Other Tree fruits Major Crops

Overview of Framework I. Coupled simulation of hydrologic cycle and crop growth: all irrigation requirements met II. Runoff, baseflow, and return flow routed through flow network; reservoir simulation accounts for irrigation diversions III. Irrigation and municipal diversions compared to water availability and instream flow requirements; curtailment in dry years IV. Iteration of coupled simulation to account for reduced irrigation in dry years ColSim

Biophysical Modeling: VIC-CropSyst, Reservoirs, Curtailment Crop Yield Irrigation Water Applied Adjusted Crop Acreage Selective Deficit Irrigation 1.Water Supply 2.Irrigation Water Demand 3.Unmet Irrigation Water Demand 4.Effects on Crop Yield Economic Modeling: Agricultural Producer Response Water Management Scenario Future Climate Scenario Inputs Modeling StepsOutputs Integration with Economics Economic Scenario

Model Scenarios: Low, Middle, High  Climate Change (Biophysical) Scenarios  Precipitation changes  Temperature changes  Water Management Scenarios  Additional Storage Capacity  Cost Recovery for Newly Developed Water Supplies  Economic Scenarios  Trade  Economic Growth  Supply is also shown for wet, dry, and average conditions

1. Columbia Basin-Scale and Columbia Mainstem 2. Example Watershed-Scale: Yakima Results

Water Supply Entering Washington Eastern: increasing Western: decreasing Top: 2030 Flow (cfs) Bottom: Historical Flow (cfs)

Water Supply Entering Columbia Mainstem Eastern: increasing Western: decreasing Top: 2030 Flow (cfs) Bottom: Historical Flow (cfs)

Snake River and Columbia River Supplies Snake RiverColumbia River

Regulated Supply vs Demand for Columbia River Basin (at Bonneville) 2030 results are for - HADCM_B1 climate scenario - average economic growth and trade Note: Supply is reported prior to accounting for demands SUPPLY: Annual : +3% Jun – Oct: -10% Nov – May: +27% DEMAND: Annual: +10%

Regulated Supply and In-Stream Flow Requirements at Key Locations Future (2030) Historical ( ) Note: Supply is reported prior to accounting for demands

Watersheds Included in Study

Out-of-Stream Demand by Watershed

Conclusions and Future Directions  Changes in supply (average of all climate scenarios)  3% increase in annual flow at Bonneville  However, 16% decrease in summer flow at Bonneville  Changes in demand (middle econ and climate scenarios)  10% increase in agricultural demand over basin  12% increase in agricultural demand over state  Some watersheds more impacted than others (see our poster on the Yakima River Basin)  Increased irrigation demand, coupled with decreased seasonal supply poses difficult water resources management questions, especially in the context of competing in stream and out of stream users of water supply.  Thinking towards the 2016 Forecast

Acknowledgements  Peer reviewers Alan Hamlet, Bob Mahler, Ari Michelson, Jeff Peterson  University of Washington Climate Impacts Group  Dana Pride  WA Dep. of Ecology

THANK YOU!

SUPPLEMENTARY SLIDES

Yakima

Yakima Unregulated Supply

Yakima Demand

Yakima Unregulated Supply and Demand: Historical vs Future Historical Middle Climate Scenario

Yakima Future Supply and Demand: Unregulated vs Regulated Supply Unregulated Supply Regulated Supply

Yakima Curtailment and Unmet Demand  Historical ( )  At least some curtailment of proratable irrigation rights 45% of years (higher than observed)  Unmet Demand: 7,200 – 278,600 ac-ft per year; average of 108,000 ac-ft per year  Future (2030s)  At least some curtailment of proratable irrigation rights for 90% of years  Unmet Demand: 14,300 – 434,000 ac-ft per year; average of 154,000 ac-ft per year

Curtailment Uncertainties  1) monthly time step of model 2) we are using a very simplified model and need something like the riverware model to capture all details 3) USBR uses a "forecast" of supply which may be different from VIC supply 4) demand does not match seasonally with entitlement expectations of USBR in managing the reservoir

Longer-Term Directions  2016 Report to State Legislature, improvements that are being considered  Groundwater dynamics  Columbia-basin scale economics (not just state-level)  Fuller inclusion of climate change scenarios  More ground-truthing

Model Calibration/Evaluation  Calibration:  Streamflows (we used calibration from Elsner et al and Maurer et al. 2002)  Crop Yields (using USDA NASS values)  Irrigation Rules (using reported irrigated extent by watershed)  Evaluation:  Streamflows (Elsner et al and Maurer et al. 2002)  USBR Diversions from Bank’s Lake (for Columbia Basin Project) USBR Diversions: 2.7 MAF/yr (with conveyance losses) VIC-CropSyst: 2.5 MAF/yr (no conveyance losses) Results in a reasonable ~20% conveyance loss

Physical System of Dams and Reservoirs Reservoir Operating Policies Reservoir Storage Regulated Streamflow Flood Control Energy Production Irrigation Consumption Streamflow Augmentation VIC Streamflow Time Series The Reservoir Model (ColSim) (Hamlet et al., 1999) Slide courtesy of Alan Hamlet

ColSim Reservoir Model (Hamlet et al., 1999) for Columbia Mainstem Model used as is, except for  Small reservoirs included for Yakima and Chelan  Withdrawals being based on VIC-CropSyst results  Curtailment decision is made part of the reservoir model Green triangles show the dam locations

Curtailment Rules (Washington State) Curtailment based on instream flow targets  Columbia Mainstem  Lower Snake  Central Region (Methow, Okanogan, Wenatchee)  Eastern Region (Walla Walla, Little Spokane, Colville) Prorated based on a calculation of Total Water Supply Available  Yakima

Yakima Reservoir Model Irrigation demand from VIC/CropSyst Curtailment rules Proratable water rights prorated according to Total Water Supply Available (TWSA) calculated each month Monthly Inflows from VIC-CropSyst Total System of Reservoirs (capacity 1MAF approx.) Objectives : Reservoir refill by June 1 st Flood space availability Instream flow targets Gauge at Parker

T – Transpiration I P – Interception capacity I – Infiltration Ir – irrigation Wd- Water demand Q – Runoff Q 01 – Drainage from 0 to 1 Q 02 – Drainage from 0 to 2 Q b – Baseflow W 0 – water content in 0 W 1 – water content in 1 W 2 - water content in 2 Tmin, Tmax – daily minimum and maximum temperature Ws – wind speed RH – Relative humidity SR – Solar radiation QbQb Q 12 T IPIP Redistribute I, W 0, W 1 and W 2 to CropSyst layers Q Q 01 W 0,W 1, W 2 T 0, T 1, T 2, I P, Wd I CropSyst VIC Ir Daily Tmin, Tmax, Ws, RH, SR, I VIC-CropSyst : Coupling Approach

Invoking CropSyst within VIC gridcell Crop 1 VIC grid cell (resolution=1/16°) (~ 33 km 2 ) Crop 2 Non-Crop Vegetation CropSyst is invoked

courtesy of Alan Hamlet The UW CIG Supply Forecast

Application of the UW CIG Water Supply Forecast  WSU is building directly off of the UW water supply forecasting effort (Elsner et al. 2010) by starting with these tools that were developed by UW Climate Impacts Group:  Implementation of the VIC hydrology model over the Pacific Northwest at 1/16 th degree resolution  Reservoir Model, ColSim  Historical climate data at 1/16 th degree resolution  Downscaled future climate data at 1/16 th degree resolution  WSU added elements for handling agriculture:  integrated crop systems and hydrology  irrigation withdrawals from reservoirs, and including some smaller reservoirs, curtailment modeling  economic modeling of farmer response

Uncertainties 1-Future climate (due to GCMs, greenhouse emission scenarios and downscaling approach) 2-Model structure (VIC-CropSyst) 3-Water management and economic scenarios 4-Cropping pattern - discrepancy between multiple data sources 5-Irrigation supply – poor data on groundwater and surface water proportions of the supply 6-Irrigation methods a)No information for upstream states b)Conveyance loss is not modeled (This is a proportion of the demand at each WRIA)

Walla

Walla Walla Supply

Walla Walla Demand

Walla Walla Supply and Demand Historical Hadcm_B1

Example WRIA Results: – Supply in WENATCHEE

Example WRIA Results - Demand in WENATCHEE

Example WRIA Results – Supply and Demand in WENATCHEE