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Interior Climate Change Water Resources Report: Columbia Basin Warmer, More Rain, Less Snow
Posted on Friday, April 29, 2011 (PST)

The Interior Department this week released a report that assesses climate change risks and how these risks could impact water operations, hydropower, flood control, and fish and wildlife in the western United States.


The report to Congress, prepared by Interior’s Bureau of Reclamation, represents the first consistent and coordinated assessment of risks to future water supplies across eight major Reclamation river basins, including the Columbia, Colorado, Rio Grande and Missouri river basins.


The “2011 SECURE Water Act Report” identifies the following climate challenges that the Columbia River Basin could likely face:


-- Projections show that temperatures throughout the Columbia River Basin above The Dalles Dam may increase steadily by 6–7 F during the 21st century. 

-- Average annual precipitation, including subbasins such as the Yakima and Snake, are projected to increase from 3.9 percent to 6.2 percent over the basin by 2050.

-- The decreased snowpack could result in decreased groundwater infiltration, runoff and ultimately lower base flows in the rivers during the summer.

-- Mean annual runoff is projected to increase by from 1.2 to 3.7 percent by the year 2050.

-- Moisture falling as rain instead of snow at lower elevations will increase the wintertime runoff with decreased runoff during the summer.


Historical and projected climate changes have potential impacts for the basin: 


-- Increased wintertime runoff and reductions in runoff during the spring and summer is likely to translate into water supply reductions for meeting irrigation demands, adversely impacting hydropower production and increasing wintertime flood control challenges.

-- Warmer conditions might cause increased stress on fisheries, reduce salmon habitat, increase electricity demand, increase water demands for instream ecosystems and thermoelectric power production and increase invasive species infestation potential.

-- Increased plant growth induced by increased spring precipitation combined with warmer, drier summers will increase forest fire risk.


Reclamation official say there are refining these preliminary Columbia Basin results through detailed basin studies on the Yakima and Snake Rivers under its WaterSMART program.


Where opportunities exist, Reclamation says it has begun adaptation actions in response to climate stresses as well as changes in land use, population growth invasive species and others. 


These activities include extending water supplies, water conservation, hydropower production, planning for future operations and supporting rural water development. For example, officials say, the Lewiston Orchards Project is exploring options to maintain stream flows required on the Nez Perce Indian Reservation for the Endangered Species Act-listed steelhead as the traditional water supply has shifted from a snowpack-driven system to a system dependent primarily on rainfall.


The full report can be found at


“Water is the lifeblood of our communities, rural and urban economies, and our environment,” said Interior Secretary Ken Salazar, “and small changes in water supplies or the timing of precipitation can have a big impact on all of us. This report provides the foundation for understanding the long-term impacts of climate change on Western water supplies and will help us identify and implement appropriate mitigation and adaptation strategies for sustainable water resource management.”


The report, which responds to requirements under the SECURE Water Act of 2009, shows several increased risks to western United States water resources during the 21st century. Specific projections include:


-- a temperature increase of 5-7 degrees Fahrenheit;

-- a precipitation increase over the northwestern and north-central portions of the western United States and a decrease over the southwestern and south-central areas;

-- a decrease for almost all of the April 1 snowpack, a standard benchmark measurement used to project river basin runoff; and

-- an 8 to 20 percent decrease in average annual stream flow in several river basins, including the Colorado, the Rio Grande, and the San Joaquin.


The report notes that projected changes in temperature and precipitation are likely to impact the timing and quantity of stream flows in all western basins, which could impact water available to farms and cities, hydropower generation, fish and wildlife, and other uses such as recreation.


"Impacts to water are on the leading edge of global climate change, and these changes pose a significant challenge and risk to adequate water supplies, which are critical for the health, economy, and ecology of the United States," added Reclamation Commissioner Mike Connor.


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