Climate Change
Changes in precipitation, snowmelt, and runoff that may occur as a result of climate change could affect water availability for irrigation, fish, and municipal uses. Depending on its severity, climate change could cause existing water supply shortages and adverse effects on streamflows and fish in the Yakima basin.
An inter-basin transfer of water to serve Roza and Sunnyside Irrigation Districts would allow water from existing reservoirs in the Yakima Basin to improve streamflows and fish habitat, along with access to upper river tributaries that would produce enhanced fish populations that would be better able to withstand habitat changes caused by climate change
The climate change report showed the Integrated Plan scenarios results for meeting the water supply needs would not meet the 70% prorationing water supply goal seven times in the 20 year period between 1985 and 2005.
Climate change will inevitably change the nature and timing of precipitation and runoff regime in the Yakima Basin. Since approximately 2/3 of the annual irrigation water supply is derived from snowmelt in the spring and early summer, the impact of reduced snow-pack could be severe, even if annual precipitation is not greatly reduced. How much water, under various climate change scenarios, will be required to compensate for the reduced snow-pack?
As published in the Environmental New Service Michael J. Scott, staff scientist at the Department of Energy’s Pacific Northwest National Laboratory in Richland, Washington, said “Our behavior where we live must change with the climate if we are to stave off economic and natural catastrophe and meet the challenge Mother Nature may hand us in the next few years.”
The Yakima River Valley is a vast fruit basket, with 370,000 irrigated acres of orchards, vineyards and other crops covering 6,150 square miles from the river’s headwaters in the Cascade Range east of Seattle to the Yakima’s terminus at the Columbia River in Richland. In a typical year, five reservoirs and stream runoff provide agriculture with 2.7 million acre-feet of water. In a typical year at mid-21st century, the amount is forecast to fall an average of 20 to 40 percent.
“The expected losses to agriculture along in the Yakima Valley over the next several decades will be between $92 million at two degrees Centigrade warming and $163 million a year at four degrees,” or up to nearly a quarter of total current crop value, Scott said.
Those losses will result from a projection based on shortage of water for irrigation. That water comes from reservoirs and runoff that are, in turn, tied directly to the amount of snow that accumulates in the Cascades over the winter, the snow-pack.