Over the last 5 years, BVFF has done 2 gravel augmentations in a side channel of the Boise River. We can see that the gravel is no longer where we put it, but the question remains, where did it go!? Is it still in the side channel somewhere? We can see what looks like new gravel accumulations in the lower side channel, but is it our gravel? This was a question that led us to do a gravel tracking project.
Jeff Jones reached out to local company Biomark, who specializes in tracking things with PIT tags. They weren't sure if their PIT tags could be detected inside of a rock, underneath 6 inches of gravel. They loaned BVFF some tags and equipment to try an experiment and were were excited to report that we could! After several rock drilling parties we had 200 tagged pieces of gravel!
After our Owyhee Gravel Augmentation in October, BVFF placed 150 pieces of PIT-tagged gravel in 4 "study plots". Today, after receiving our Stream Alteration Permit from IDWR and USACE and permissions from Idaho DSL and Ada County, BVFF placed 50 pieces of PIT-tagged gravel in our Boise River side channel, along with 0.9 cubic yards of 3/4" round washed gravel. The plan is to use a PIT Tag Detector and sweep the side channel each Fall for 5 years, to see where the tagged gravel ends up. Observations will help guide future gravel augmentations.
While we only added around a cubic yard of gravel today, it's location should be good for rainbow trout spawning this April/May. Given the lower snowpack, we don't anticipate high spring flows, which means the gravel is likely to mostly stay put this year.
For more information about our past gravel augmentations, see these articles:
LESSONS LEARNED
BVFF continues to work on trout habitat improvements in the side channel, including working with the flood district to improve woody cover for trout. We have had the opportunity to accompany Idaho Fish and Game on a couple of their fall trout fry surveys, and it has been gratifying to see good numbers of rainbow and brown trout fry in the side channel.
Going into the first gravel augmentation we thought that gravel was the lone missing ingredient for trout spawning. But what we have observed is that side channel connectivity is just as important as gravel--as without adequate water in the side channel, brown trout do not spawn. The IDF&G trout fry surveys have also highlighted the value of woody cover to trout fry.
IDAHO WATER QUALITY WORKSHOP
Last week, BVFF shared details on our gravel tracking project at the the Idaho Water Quality Workshop. BVFF and Trout Unlimited also shared details about Boise River gravel augmentations done over the last 20 years, including observations of gravel movement. We put together a poster for the March 2026 Idaho Water Quality Workshop that highlights some of our observations of gravel movement in our side channel (shown below).
It is impressive that a volunteer organization has been able to put together this gravel tracking project. Special thanks goes to BVFF club member Jeff Jones for his efforts to lead the project --it would not have happened without his expertise and leadership. We would also like to thank Nick Porter and Biomark for their partnership on designing and participating in the study. And Zack Kirk from Ada County for permission to put some gravel into the side channel for this study.
