A study expected to be published in the spring 2013 science journal Climatic Change reveals that over the last 100 years linear trends of stream flow have changed dramatically on Columbia River Basin tribal reservations and historical tribal lands.
The changes to flows, along with warming water, could play a significant role in the life cycle of salmon. A prime example of the research shows that the spring snow melt in the Umatilla River Basin is occurring a full month sooner than it was 75 years ago.
The research is a “retrospective” study of the effects of climate change on Columbia River Basin watersheds, according to its author, Kyle Dittmer, hydrologist-meteorologist, at the Columbia River-Inter Tribal Fish Commission, Portland, Ore.
According to Dittmer’s research, which included flow gauge analysis over the last 75-100 years:
-- The average April-July flow volume declined by 16 percent.
-- The median runoff volume date has moved earlier by 5.8 days.
-- The spring flow onset date has shifted earlier by 5.7 days.
-- The trend of the flow standard deviation (i.e. weather variability) increased 3-11 percent.
-- The 100-year November floods increased 49 percent.
“Continuation of these climatic and hydrological trends may seriously challenge the future of salmon, their critical habitats, and the tribal peoples who depend on these resources for their traditional livelihood, subsistence, and ceremonial purposes,” Dittmer wrote in his paper’s abstract.
Dittmer’s work will contribute to and help support one major “group paper” that will assess climate change impacts past, present and future on the water resources throughout Indian Country, including the continental United States, Hawaii, and Alaska. Additionally, Dittmer’s Pacific Northwest paper will be published alongside the “group paper” in a special themed issue on tribes and climate change in the Climatic Change journal.
Dittmer’s research indicates several major challenges for fish over the next several decades. He doesn’t say it’s too late for salmon, but he does say that time is of the essence.
“Salmon are a very adaptable species,” Dittmer said. “The problem is the rate of climate change. The increase is expected to accelerate here in the 21st Century … No matter how much habitat restoration we do in the mountains, the real major problems are going to occur 20 to 30 years from now.”
Already the region is seeing how the effects of warmer water are affecting salmon coming up the Columbia River. Fish that routinely would be heading upstream often wait below Bonneville Dam for one to four weeks before they start migrating in mid-summer when the surface water cools.
“The concern is that salmon will not adapt fast enough and at some point they’ll just say ‘screw it, I’ll go to Alaska.’ They’ve done that before. Over the last 150 years, Columbia basin salmon bones have been found in different lakes in British Columbia and Alaska. If PNW temperatures continue to climb, salmon will head northward instead of migrating up the Columbia.”
Keeping water cool and hospitable is a priority goal. Dittmer said tribes have long worked on stream and bank restoration in tributaries, which helps to keep tributary waters cool and clean, but it’s the mainstem Columbia and Snake Rivers that will be the “bugaboo.”
The rate of change is most noticeable in the Umatilla River Basin near the headwaters east of Gibbon on the Umatilla Indian Reservation.
“The climate change impacts on the water around the Umatilla Reservation are the most extreme of all basins analyzed,” Dittmer said.
As an example, Dittmer pointed to the dramatic change of the Umatilla River spring flow onset, also known as the freshet. Based on the annual snow melt cycle from 1934-2012, the annual snow melt cycle shows a 31-day shift earlier in time.
“That’s a whole month earlier,” Dittmer said. “That’s outrageous.”
Most basins have shown an earlier freshet of from 1-14 days.
Dittmer suggests that the melt is occurring earlier for headwaters above what he calls a “sweet spot,” although most would not consider it particularly sweet.
“I think those areas are in a sweet spot of 3,000 to 4,000 feet elevation,” he said. “Warmer temperatures in winter result in mid-winter snow melt. Even just a slight temperature warming can make a huge difference.”
Such research should sound “alarm bells” for freshet shifts of even two weeks.
“That time disrupts ecological processes. Food sources for salmon may not be ready by the time the fish are ready to mull around in the streams.”
The early snow melt should be a huge concern for the Umatillas because it will result in less snow melt river runoff in June and July when flows already are low. The trends could have significant impacts on the Umatilla Basin Project and other water exchange programs designed to take water from the Columbia and Umatilla Rivers while at the same time protecting flows for migrating fish.
According to his research, if the trend continues there will be “definite ramifications as far as maintaining summer flows.”