In an effort to lower stream temperatures to ensure the long-term health and stability of the Big Wood River, the Department of Environmental Quality is seeking public comment on proposed Total Maximum Daily Loads (TMDL).
A TMDL is a calculation of the maximum amount of a pollutant that a water body can receive and still meet water quality standards, as defined by the DEQ. Pollutants include bacteria, sediment, nutrients and temperature.
"In this case the pollutant is excessive temperature caused by heat loading," a news release from the DEQ states. "Studies of Big Wood River and Rock Creek indicate that stream temperatures are above desired levels to protect the health of cold water fish such as rainbow trout."
The main contributors to increased temperature are solar loading due to diminished streamside vegetation and discharges from wastewater treatment plants owned by the cities of Ketchum and Hailey and The Meadows LLC, a private mobile home park south of Ketchum, according to the DEQ.
The TMDL program began in 2002 after the Big Wood River Watershed Management Plan was implemented.
"When the original TMDL (plan) was written it only included sediment, phosphorous and bacteria, and temperature would be rolled in at a future time," explained Balthasar Buhidar, manager of water quality protection in the DEQ's Twin Falls region. "That future time is now."
The DEQ is already immersed in projects in the Big Wood basin to combat sediment, phosphorous and bacteria.
Buhidar said the primary method of lowering temperatures is to increase canopy covers along the Big Wood River, Rock Creek and associated tributaries.
The wastewater treatment plants have temperature targets that, if exceeded, could result in "some kind of mitigation," Buhidar said. But the plants are not in danger of being shut down.
"Nothing like that," he said.
Buhidar said the DEQ has some data on rising temperatures in the Big Wood River but "not enough to really justify how much temperature has been increasing."
But the department does know how much the canopy cover, and shade in the river, has decreased from historical levels.
"From North Fork to the Glendale diversion, it's looking like 12 percent," he said.
So who will pay for the project, materials, and man-hours to complete the work on the ground?
"This will be a multi-agency stakeholder effort. It's not just the DEQ," Buhidar said.
The watershed advisory group, Blaine Soil Conservation District, Natural Resources Conservation Service, Bureau of Land Management and Forest Service will all be involved in the effort, Buhidar said.
Public comments on the proposed temperature TMDLs, which can be viewed online at www.deq.idaho.gov/public/comment.cfm, will be accepted through March 30.
Questions and comments should be directed to Balthasar B. Buhidar, DEQ Twin Falls Regional Office, 1363 Fillmore St., Twin Falls, ID, 83301. Comments can also be mailed electronically to firstname.lastname@example.org.