Hydrology and Water Resources

Key Findings

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The Climate Impacts Group’s (CIG) research on the relationship between climate and Pacific Northwest (PNW) hydrology and water resources has made significant contributions to our understanding of climate influences on PNW water supplies, decision-support for water resource management, and the role of institutional arrangements in shaping vulnerability to climate variability and change. Key findings from this research include the following.

20th Century Hydrologic Trends

In characterizing trends in 20th century PNW hydrologic conditions, CIG has:

Impacts of Climate Variability on PNW Hydrology and Water Resources

The CIG has assessed the seasonal and interannual consequences of climate variability for PNW hydrology and water resources, finding that:

Climate-based Seasonal Streamflow Scenarios

In its efforts to support the use of climate information in PNW water resource management, the CIG has:

Impacts of Climate Change on PNW Hydrology and Water Resources

The CIG has investigated the projected impacts of climate change for PNW hydrology and water resources, finding that:

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Climate Change Impacts on the Columbia River Basin.

Figure 4 Climate change impacts on the Columbia River basin.
(Left) Changes in the average naturalized hydrograph at The Dalles. Observed “naturalized” historic streamflows (water management effects removed) are compared to the range of simulated flows (shaded) for 2040, derived from four GCMs used in 2001 IPCC report.
(Right) Changes in average April 1 snowpack extent in the Columbia River Basin as simulated by the VIC hydrology model for 20th century climate (1961- 1997) and a middle-of-the-road scenario of future climate. Snow outside the basin is not shown.

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Reliability of Columbia Basin water resources objectives in the 2040s

Figure 5 Reliability of Columbia Basin water resources objectives in the 2040s under for four climate change scenarios, compared to current, given the current water resources operating system. The black bar shows the simulated present-day reliability of each management objective, while the blue bars show the reliability under the four climate change scenarios. Reliability is defined as the modeled (or observed) probability of meeting a particular objective. For example, an objective with 90% reliability will be met in 90% of the months of the simulation. The four scenarios were derived from the global climate models ECHAM4, HadCM2, HadCM3, and PCM3.

Impacts of 2040 Climate Change and Regional Growth on the Bull Run Watershed.

Figure 6 Impacts of 2040 climate change and regional growth on the Bull Run watershed. In a research partnership with the City of Portland (Oregon), CIG researchers used four global climate models to analyze the impacts of climate change in 2040 on the City’s Bull Run watershed. The study found that while population growth has the largest impact on future water supply needs, the additional impact of climate change on supply and demand by 2040 is considerable. Climate change would increase supply needs by 50% of the amount required to meet population growth alone.

Climate Change Streamflow Scenarios

CIG removed the bias that typically results from hydrologic simulation models to create climate change streamflow scenarios for use in water resources planning. The streamflow scenarios are numerically consistent with and, for purposes of evaluating system performance, directly comparable to observed streamflow time series. The development of these scenarios, which are used in place of historic streamflow records, gives water resources managers the ability to easily and inexpensively evaluate system vulnerabilities to climate change by allowing for direct incorporation of the streamflow scenarios into existing water resources planning methods (such as critical period analysis). The climate change streamflow scenarios are available here.

Institutional Sources of Climate Vulnerability

The CIG has analyzed the institutional context of regional water resources management, including institutional sources of vulnerability to climate, finding that:

Climate Variability, Climate Change, and Evolving Water Policy

The CIG has evaluated the implications of climate variability and change for water resources development and evolving water policy, finding that climate change is likely to lead to transboundary tensions between Canada and the United States given the projected effects of climate change on snowpack and the timing of spring runoff in the U.S. portion of the Columbia River Basin. This potential is further increased by:

Despite these problems, the agreements within the CRT and related transboundary agreements present potential opportunities for the mutually beneficial release of water from Canadian storage in summer to help meet U.S. instream flow objectives. One opportunity comes from the increased marketability of Canadian hydropower as a result of growing summer energy demand outside the PNW (Hamlet 2003; Hamlet et al. 2010).

Climate Change Impacts on the PNW Ski Industry

For ski areas at moderate elevation, the CIG has found that even modest increases in PNW temperature and precipitation as a result of climate change could significantly decrease revenues by shortening the length of the ski season and reducing patronage due to undesirable ski conditions (as a result of increased winter rain). Snow model simulations show that average ski conditions at Snoqualmie Pass (Washington) ski area, whose base elevation is about 3000 ft, could change dramatically by 2025. The simulations suggest that the likelihood of opening by Dec. 1 could decline by 50%, average season length could decline by 28%, and the likelihood of rain when the ski area is open could increase by 25%. The changes in snow conditions by 2025 are less pronounced for Stevens Pass (Washington), whose base is at about 4050 ft. The simulations for Stevens Pass suggest that the likelihood of opening by Dec. 1 could decline by 25%, average season length could decline by 14%, and the likelihood of rain when the ski area is open could increase by 50%.

Research Awards

CIG publications on hydrology and water resources have been recognized nationally by peer-reviewed journals. CIG research publications have won the: