By Greg McMillan
To paraphrase Bob Dylan’s song “Subterranean Homesick Blues,” you don’t need a weatherman to know it’s suddenly become hot outside. And the lower Deschutes River is warming with the weather. As shown in this graph from the temperature gauge at Moody, the river hit nearly 72 degrees F. on Sunday, June 7. More hot weather is in the forecast.
Dylan’s actual line was, “You don’t need a weatherman to know which way the wind blows.” And we know which way the wind is blowing regarding temperature management at the Pelton-Round Butte Dam Complex using the Selective Water Withdrawal (SWW) Tower.
The dam operators have been using a temperature management model that seeks to “eliminate the thermal presence of the dams.” Combining surface (warm) and bottom (cool) water withdrawal in the SWW Tower is supposed to do this.
Combining the temperatures of the Lake Billy Chinook tributaries and the air temperature at Redmond Airport and plugging them into a statistical equation determines the temperature goal for water discharged from the dam complex. The warmer it gets, the warmer the discharge from the dams should be according to this model.
This is analogous to turning up your home’s furnace during hot weather, instead of turning on the air conditioner. The dam operators, according to their Water Quality Management and Monitoring Plan (WQMMP) are to further warm the river when it’s already warming due to weather conditions. This makes no sense from a biological perspective. When is it ever better to warm a salmon-trout-steelhead river?
Last year the dam operators lowered the temperature of the lower Deschutes by increasing bottom water draw from 15% to 45% on July 18 and 19. The Deschutes River Alliance hopes and advocates for the dam operators to again provide cooler water for the lower river during the hot months ahead. Only this year, do it sooner.