If current trends continue, the Big Wood River might need to be renamed the Medium Wood.
The upper Big Wood River is suffering from unusually good health and high levels of biological productivity, but it is a resource that could change for better or worse. One of the key limiting factors and primary agents of change in the river system is a transition away from the amount of wood that historically fell into and lodged along the Big Wood River's banks, according to a study released by the Wood River Land Trust last week.
People have built their homes close to the river, and they have protected their land by shoring up the river's banks with stones and structures. People are keeping their back yards, but the river is increasingly hungry for more dead trees and brush, something biologists refer to as "woody debris."
"Woody debris is another critical component of trout habitat and a healthy river," according to the introduction of the study, called Big Wood Fishery Assessment: Healthy Waters, Healthy Future. "Removal of woody debris can increase stream velocities and adversely affect the channel and riparian vegetation."
For the last 18 months, the Hailey-based land trust has undertaken the study to quantify what's going right and what isn't in the Big Wood River. The study could take another year or two to complete and implement.
Land trust representatives released the first phase of the document at a lunch meeting at The Roosevelt Tavern in Ketchum on Friday.
One of the goals is to find out how the fishery can be maintained or improved and how to prevent growth from overrunning one of the valley's most prized natural assets.
"The project is designed to help us identify the best places to focus on along the river when we buy, conserve or restore properties," said Kathryn Goldman, the land trust's projects coordinator. "The phase one report examines the major factors that limit the fishery and what we as an organization and the larger community can do to address the problems."
The study follows on prior research and splits the river into three stretches. They are divided roughly by the Glendale diversion south of Bellevue, Warm Springs Creek and the North Fork of the Big Wood River. The river's health is limited by different factors in the different reaches of river, Goldman said.
"From Warm Springs Creek north to the headwaters, the fishery is limited primarily by natural conditions such as the colder water temperatures and lack of nutrients in the river system," according to an executive summary of the study.
Below the Glendale diversion, water quantity is the primary limiting factor. That portion of the Big Wood often runs dry during summer months.
The middle section, between Glendale and Warm Springs Creek, is the most productive stretch of the Big Wood River.
"This is the area that offers the greatest opportunity to improve the health of the fishery with restoration efforts and land protection projects," Goldman said.
Habitat is the largest limiting factor, she said. The river has an ongoing hunger for dead trees and brush that is not being met at historic levels.
"Things have changed," Goldman said. "You can see that the river channel has changed a great deal due to all the channelization, rip-rapping and diking."
Part of the solution will be to protect as open space some of the properties that remain undeveloped along the river's edges. There, the river will be allowed to carve out new meanders and bull over trees according to its natural instincts.
According to the phase one study, there are several crucial arenas to pursue to improve or maintain the Big Wood fishery: public education and outreach, restoration and protection of the river corridor and advocating land-use regulations that help the natural river system to thrive.
And, according to Goldman, the findings of phase one have clearly demonstrated a need for further research.
In phase two, the land trust will concentrate its efforts on the stretch of river between Warm Springs Creek and the Glendale diversion. Goldman said she would begin examining historic aerial photos of the river system and compare them with current photos. She will also look at river alteration permits that have been sought and granted along the river corridor.
