Water temperature has a significant effect on the migration behavior of chinook and other species of salmon. Optimal temperatures for both upstream and downstream migration of chinook salmon range from about 46 - 59oF. Beyond about 72oF the amount of dissolved oxygen in the water is reduced to a point that can stress and kill the migrating fish.1 For this reason, water standards in both Oregon and Washington require that 7-day and 1-day average water temperatures respectively be maintained below 68oF.2
As water pools behind dams it warms throughout the summer months. The graphs below show the changing water temperature conditions at the Lower Granite Dam, the first major dam that migrating juvenile chinook encounter on the Snake River as they make their way downstream to the Pacific and the last dam encountered by returning chinook making their way upstream to the their South Fork Salmon River spawning grounds.
1) This type of repeating pattern is known as a sinusoid. How often does the pattern repeat? What is the range of values from lowest to highest temperature?
2) Adult chinook salmon making their way from the ocean back to the South Fork of the Salmon River normally pass the Lower Granite
Dam in a two month period from May through June. Juveniles swimming
downstream to the Pacific pass the dam in April and May of each
year.3 Examine and describe the decade-to-decade changes
in the average river temperatures behind the Lower Granite Dam
particularly during these time periods.
3) River managers attempt to control temperature to accommodate
traveling fish. Do some research to discover how this is done on the
Columbia River and, judging from the evidence in the graphs, analyze
the effectiveness of efforts to control the water temperature.
1Phillip A. Groves and James A. Chandler," Physical Habitat and Water Quality Criteria for Chinook Salmon Associated with the Hells Canyon Complex," Idaho Power Company, 2003.
2Dwight Q. Tanner, et al, "Total Dissolved Gas and Water Temperature in the Lower Columbia River, Oregon and Washington, 2007: Quality-Assurance Data and Comparison to Water-Quality Standards," US Geological Survey, 2007.
3Columbia River DART, Columbia Basin Research, University of Washington.
graph data from Columbia River DART, Columbia Basin Research, University of Washington.