They predict an average of 2 degrees warming by the 2020s and 4 degrees by the 2050s. It also used past natural climate variations to predict what problems might be caused by even small temperature increases. It is snowpack in the mountains, melting in the late spring and summer, that provides much of the water used by humans and ecosystems during the Northwest's dry summers. Columbia River flows peak in June, but the yearly high point could come a month earlier under the study's models of global warming. Under the scenario, summer flow would be sharply reduced, cutting water available for irrigation, adequate flows for salmon and urban supplies west of the Cascade Mountains.
Scientists suggest compensating with major changes in how the water supply is managed and allocated.
To decrease demand, the report suggests reducing irrigated acreage, irrigating more efficiently and changing to a market-based system to set water prices based on supply and demand. Those efforts could be complicated by more people in Washington, Idaho and Oregon. Regional population is expected to grow 50 percent in the next 50 years. Washington is expected to gain 2 million residents in 20 years, or the equivalent of three new Seattles, Miles said. The report also suggests ways to increase water supply, including finding new sources such as ground water and developing new water storage systems such as reservoirs.