It is axiomatic that water defines a river, but it is particularly so for the Columbia River, where the unique geography and climate of the river basin contribute to the tremendous volume of annual runoff — fourth-largest in North America behind Mississippi, Mackenzie, and St. Lawrence. Historic precipitation patterns influence ecological processes such as the location and abundance of fish and wildlife populations, human uses of the land, and regimes of fire and flood.

The climate west of the Cascade Mountains is influenced by the proximity of the Pacific Ocean. Winters are mild, and rainfall is frequent and at times heavy. Snowfall is rare west of the Cascades except at the higher elevations of those mountains and in the Coast Range. In the low-lying areas of the Columbia and Willamette river valleys snow usually only occurs within a period of weeks in January and February. The climate east of the Cascades is markedly different, a continental climate of cold, snowy winters and warm, dry summers. The continental climate extends into British Columbia, where successive mountain ranges also catch winter storms and snowfall is frequent and heavy, but summers generally are warm and dry.

Annual precipitation varies from 45 inches in the Portland/Vancouver metropolitan area, to 100 inches or more in the heart of the Columbia River Gorge, to fewer than 8 inches in the rain shadow area immediately east of the Cascades. Most of the interior Columbia River Basin receives between 12 and about 30 inches of precipitation annually, with the exception of the Snake River Plain in southern Idaho, which is drier.

The mountain ranges within the Columbia River Basin typically receive 100 to 200 inches of snow annually; this is one reason for the Columbia’s huge annual runoff volume, which averages 192 million acre-feet. The annual spring freshet, when the snow melts and runoff peaks in the spring and early summer, historically provided the transit to the estuary and ocean for juvenile salmon and steelhead. Dams altered this flow regime by catching and holding water in reservoirs for winter power generation, thus reducing the volume and velocity of the spring flow.

Climate also affects growing seasons in the Columbia River Basin. At higher elevations, the season can last as few as 30 days. In the intermontane valleys and plateaus, however, such as the interior plateau that stretches mostly unbroken from central Washington to central Oregon, and in the comparatively damp Willamette Valley of Oregon, growing seasons are 150 to 200 days long.

Air quality in the Columbia Basin is heavily affected by wind, and the interior parts of the basin can be very windy. The average wind speed in the Columbia River Gorge, where the steep walls can act as a funnel, is 10 miles per hour. This is primarily why the Gorge has become so popular with wind surfers. Frequent and sustained winds of 20 miles per hour or faster are common. Farther to the east, in central and southeastern Washington and northern and northeastern Oregon, the fine-grained loessal soils are particularly susceptible to wind erosion, and periodic dust storms in the spring and summer can raise clouds of roiling dust that halt traffic on the inland highways. It is not unusual for eastern Washington to be blanketed with dust from spring and summer winds from the west. The frequency of sustained winds has prompted a renaissance of wind-power developments in southeastern Washington and northeastern Oregon. Long rows of 100 or more spinning turbines are becoming an increasingly common sight on the mostly treeless ridgetops.

Periodically the Gorge funnels wind, hot in summer and cold in winter, into the Portland/Vancouver area, the largest population center in the Columbia River Basin, with dramatic effects. In summer, the hot wind can blow temperatures to over 100 degrees F and cause a marked drop in humidity in the Portland area. The winds continue down the river all the way to Astoria, where the temperature might climb into the 80s or 90s. Yet just a few miles south of Astoria, where the river wind doesn’t reach, it will be 30 degrees cooler and foggy. In winter, cold winds blowing down the Gorge can chill the Portland area to well below freezing. When a warm, wet weather system overrides the surface-level cold air, the temperature difference between the surface and about 2,000 feet in elevation can be 15 or 20 degrees — enough to keep the inevitable rain from turning to snow before it hits the ground. These storms can be vicious, dumping up to 10 feet of snow in the western end of the Gorge, although that has not happened since the early 20th century, but more commonly laying down a coating of solid ice. Such a storm paralyzed the Portland area for four days in January 2004.

Climate change impacts and the Columbia River Basin

A significant proportion of scientific opinion, based on both empirical data and large-scale climate modeling, holds that the Earth is warming due to atmospheric accumulation of carbon dioxide (CO2), methane, nitrous oxide, and other greenhouse gasses. The increasing atmospheric concentration of these gasses appears to be largely from human activities, in particular, the burning of fossil fuels. The effects of warming may include changes in atmospheric temperatures, storm frequency and intensity, ocean temperature and circulation, and the seasonal pattern and amount of precipitation. Possible beneficial aspects to warming, such as improved agricultural productivity in cold climates, on balance appear to be outweighed by adverse effects such as increased frequency of extreme weather events, flooding of low-lying coastal areas, ecosystem stress and displacement, increased frequency and severity of forest fires, and northward migration of warm-climate diseases. While there is general agreement on the fact and impacts of global warming, significant uncertainties remain regarding the rates and ultimate magnitude of warming and its effects.

Section 4 (e)(2) of the Northwest Power Act requires the Council to give “due consideration” to environmental quality in developing its power plan and fish and wildlife program, and in periodically reviewing and revising them. The Council has long recognized the potential impacts of a warming climate to the region’s power supply. Hydropower, which relies on flowing water, and thus snow and rain, is the source of about half of our regional power supply, on average, and as much as 75 percent or more during certain times of the year, such as during the spring snowmelt runoff. In February 1989 the Council sponsored a workshop on the greenhouse effect and global warming, and in its 1991 Power Plan the Council wrote, “Climatologists have argued that increasing concentrations of greenhouse gases may cause the Earth’s temperature to increase at unprecedented rates, with potentially disastrous consequences.” These included, according to the plan, “dramatic changes in local climates around the world” (See Volume II, Chapter 9, Page 719). As mitigation, the Council recommended improved power plant efficiencies, carbon-capture technologies at thermal power plants that use coal or natural gas, and tree planting to capture carbon in the atmosphere. The 1991 Plan considered coal “the most environmentally troubling resource” and theorized that “should the worst fears of scientists be realized, operating coal plants could be assessed a tax on carbon dioxide emissions or, at the extreme, be prohibited from operating” (Page 732).

Since 1991, concern about the impacts of global warming and climate change have increased, and some effects already have been evident – warmer summers and winters, more rain and less snow in winters, higher water temperatures in rivers and related impacts on fish. In July 2015, for example, more than a quarter million adult sockeye that were counted at Bonneville Dam as they returned from the ocean to spawn were not counted at McNary Dam 146 miles upriver. It is believed the fish died in the unnaturally warm water of the river, warmed by days of high air temperatures.

In its 2015 Power Plan, also known as the Seventh Power Plan, the Council acknowledges, in Appendix M, its obligation to investigate the possible impacts of climate change (“due consideration for environmental quality”) on the region’s power system and to recommend actions to maintain the adequacy, reliability, efficiency, and economy of the system whenever appropriate. The climate prediction for the Northwest, downscaled from Intergovernmental Panel on Climate Change analyses, is for less snow and more rain during winter months, resulting in a smaller snowpack, earlier spring runoff, and lower summer river flows. Winter electricity demands would decrease with warmer temperatures, easing generating requirements. In the summer, power demand driven by air conditioning and irrigation would increase.

The Council addresses carbon policies and methane emissions in Chapter 3 of the 2015 Power Plan, noting that the plan supports policies that cost-effectively achieve state and federal carbon dioxide emission reduction goals while maintaining regional power system adequacy. In the plan the Council acknowledges that in light of future demand growth, it may be necessary to build new natural gas-fired generating plants, but that the Council’s overall resource strategy is to minimize the need to develop new gas-fired generation by meeting most future energy and capacity needs with energy efficiency and demand response.

The Council will revisit the carbon question and climate change impacts to the power supply in the next power plan, which is scheduled for completion in 2021. Meanwhile, the Council also addresses climate change impacts in its Columbia River Basin Fish and Wildlife Program. The 2014 Program, which the Council plans to revise in 2020, addresses the impacts of climate change on fish and wildlife and recommends that future planning and implementation of projects to protect and enhance fish and wildlife populations affected by hydropower dams should include explicit consideration of the possible effects of climate change on focal habitats and fish and wildlife populations, using adaptive management principles (Page 57).

These impacts could be addressed, according to the program, by determining whether climate change effects are altering or are likely to alter critical river flows, water temperatures or other habitat attributes in a way that could significantly affect fish or wildlife, either directly or by affecting the success of current mitigation efforts. If so, the program recommends, the federal river and hydropower management agencies, such as the U.S. Army Corps of Engineers and the Bonneville Power Administration, should evaluate whether alternative water management scenarios, including changes in flood control operations, could minimize the potential effects of climate change on river flows and temperatures.

Meanwhile, the warming continues. Reviewing regional and electricity data for 2018, the Council’s power planning staff reported in the fall of 2019 that the 2018 winter was warmer on average than the previous 91 winters. This probably was the reason for a 9 percent decrease in heating requirements in 2018 compared to 2017 and, because the summer also was warmer, a 23-percent increase in air conditioning requirements. If there is an upside to the warming, one might be that residential monthly electricity bills declined in the winter of 2018 compared to the previous winter, the power planning staff reported.