Designing Hydrologic Modeling Studies to Support Diverse Climate Change Planning Needs in the Columbia River Basin Alan F. Hamlet Amy K. Snover Kurt Unger Philip W. Mote Dennis P. Lettenmaier JISAO/CSES Climate Impacts Group Dept. of Civil and Environmental Engineering University of Washington WA State Department of Ecology

Simulated Changes in Natural Runoff Timing in the Naches River Basin Associated with 2 C Warming Impacts: Increased winter flow Earlier and reduced peak flows Reduced summer flow volume Reduced late summer low flow

PNW Pilot Climate Change Planning Efforts: West Side Cascades Partnerships: Portland Water Bureau Seattle Public Utilities Tualitin Basin White River-Lake Tapps Snohomish River Basin King Co. Columbia Basin Partnerships: Northwest Power and Conservation Council (BPA) US Bureau of Reclamation (Boise) Seattle District Corps of Engineers Idaho Department of Water Resources

Recession of the Muir Glacier On the left is a photograph of Muir Glacier taken on August 13, 1941, by glaciologist William O. Field; on the right, a photograph taken from the same vantage on August 31, 2004, by geologist Bruce F. Molnia of the United States Geological Survey (USGS). According to Molnia, between 1941 and 2004 the glacier retreated more than twelve kilometers (seven miles) and thinned by more than 800 meters (875 yards). Ocean water has filled the valley, replacing the ice of Muir Glacier; the end of the glacier has retreated out of the field of view. The glacier’s absence reveals scars where glacier ice once scraped high up against the hillside. In 2004, trees and shrubs grow thickly in the foreground, where in 1941 there was only bare rock. Aug, 13, 1941 Aug, 31, 2004 Image Credit: National Snow and Ice Data Center, W. O. Field, B. F. Molnia http://nsidc.org/data/glacier_photo/special_high_res.html

Collapse of the Larsen B Ice shelf, Antarctica March 5, 2002

Annual area (ha × 106) affected by MPB in BC 1910 1930 1950 1970 1990 2010 1.0 2.0 3.0 4.0 5.0 6.0 Year 8.0 7.0 1999 2001 2000 2003 2002 Annual area (ha × 106) affected by MPB in BC 2005 9.0 2004 Bark Beetle Outbreak in British Columbia By last year, the total area of beetle-caused mortality spread over some 10 million hectares (Figure courtesy Allen Carroll)

Trends in April 1 SWE 1950-1997 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

spring flows rise and summer flows drop 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 Spring snowmelt timing has advanced by 10-40 days in most of the West, leading to increasing flow in March (blue circles) and decreasing flow in June (red circles), especially in the Pacific Northwest.

An Opportunity to Provide Improved Access to Hydrologic Scenarios for Planning As the public and professionals in the water management and policy arenas have become increasing concerned about the impacts of climate change on PNW water resources, demand for hydrologic scenarios suitable for planning purposes at a range of spatial scales has increased dramatically. Currently there does not exist an up-to-date, comprehensive, and self-consistent data base of hydrologic scenarios for the Columbia River basin that is suitable for the range of planning activities the Climate Impacts Group is being asked to support.

WA House Bill 2860 $16 Million for studies related to enhancing water supplies in the Columbia River basin for irrigation and municipal water supply. Up to $200 Million for implementing improvements identified by these studies. Answers to FAQ regarding WA 2860 from the Department of Ecology website: http://www.ecy.wa.gov/pubs/0611014.pdf

Water Planning Framework Schematic of a Typical Water Planning Framework Observed Streamflows Planning Models System Drivers

Climate Change Scenarios Schematic of Climate Change Water Planning Framework Observed Streamflows Planning Models Altered Streamflows Climate Change Scenarios System Drivers

The Need to Encompass Multiple Spatial Scales

Large Scale Planning Studies Examples: Hydro System Performance Flood Control Main Stem ESA Transboundary Issues Large-Scale Irrigation Impacts

Medium Scale Planning Studies Examples: Water Supply Planning Yakima Basin Okanogan Basin Methow Walla Walla Basin WA State Water Resources Inventory Areas

Observed 20th century variability Curves are fits to ln(CO2) for A2 (solid) and B1 (dashed) Warming ranges are shown for 2020s, 2040s and 2090s relative to 1990s. Central estimates: 0.7C by 2020s, 1.7C by 2040s, 3.2C by 2090s. Pink box shows +/- 2 sigma for annual average temperature (sigma=0.6C). Red lines show previous generation of change scenarios. Until mid-century, emissions scenarios play a minor role in the temperature impacts. Towards the end of the century they play a big role. Conclusions: 1) Adaptation will be an essential component of the response to warming over the next 50 years. 2) Mitigation of greenhouse gas emissions will play an important role in determining the scope of late 21st century impacts. 0.4-1.0°C Pacific Northwest

Observed 20th century variability % -1 to +3% +6% +2% +1% Curves are fits to ln(CO2) for A2 (solid) and B1 (dashed) Precip changes are shown for 2020s, 2040s and 2090s relative to 1990s. Central estimates: 1% by 2020s, 3% by 2040s, 6% by 2090s. Pink bar shows +/- 2 sigma for PNW annual precip. Observed 20th century variability -1 to +9% -2 to +21% Pacific Northwest

Daily Precipitation, Tmax, Tmin Result: Daily Precipitation, Tmax, Tmin 1915-2003

Schematic of VIC Hydrologic Model and Energy Balance Snow Model 6 km 1/16th Deg. 6 km PNW Snow Model

Streamflow Locations Currently Under Consideration Blue = Large Scale Planning Sites Green = Snake River Sites Red = Additional Sites in WA Partnerships with OR, ID, and BC are being discussed with the intent to extend the number of sites in these areas.

Alternate Approach: DHSVM Developed in the UW Land Surface Hydrology Research Group at UW for over a decade a research tool, also is used operationally applied to small catchments DHSVM: Distributed Hydrology-Soil-Vegetation Model

Medium Scale Planning Studies WA State Water Resources Inventory Areas

Some Potential Advantages of DHSVM Approach Increased spatial resolution down to the watershed scale Increased temporal resolution (high and low flow extremes) Water temperature simulations Simple ground water scheme improves base flow simulations Future access to sediment transport capability (research)

Proposed Downscaling Approaches Statistical Downscaling (GCM) 10 scenarios Dynamic Downscaling (nested MM 5) 2 scenarios Improvements in downscaling techniques will be implemented to allow evaluation of daily effects on flooding and low flow events.