Owyhee River Gravel Augmentation Study

The Owyhee River has an amazing brown trout population. Initially when the dam was built, the river below  was intended to just be a put-and-take fishery but the stocked brown trout  were able to successfully spawn and their population exploded. The best habitat for brown trout extends from the dam down 15 miles to Snively Springs but the density of the brown trout population is notably higher in the first 5 miles of the river. The Oregon Department of Fish and Wildlife (ODFW) has been counting brown trout redds on the Owyhee River for over 15 years and one consistent trend is that even though water temperatures and quality are excellent down through the lower reaches, there are significantly fewer redds per mile there compared to upstream.

BVFF has been volunteering with ODFW to help count redds on the Owyhee river for several years and has been talking with Oregon fish biologists Dave Banks and Kirk Handley about the possibility of doing a gravel augmentation on the river to increase the amount of spawning in the lower reaches of the river. For an area to be suitable for a gravel augmentation it needs to have the right water depth and velocity for brown trout to spawn plus logistically be close enough to the river for us to add the gravel. Working with ODFW we have identified a riffle and run below an intermittent creek called Sand Hollow that looks promising as well as a tail-out nearby below the lower concrete bridge.

In November and December of 2021 BVFF volunteers met at the Owyhee river to help ODFW to evaluate the suitability of the proposed gravel augmentation sites. We started by measuring the depth, flow and bottom composition at redd locations in a highly successful spawning run in the upper river, below the Hollywood Hole. We found that browns typically built their redds in water depths of 1 – 2 feet in riffles but would build their redds as shallow as 6 inches deep in a riffle to as deep as 3 feet as the riffle dropped into a run.

We then took cross-sections of the proposed augmentation sites to compare with the successful spawning area and we counted brown trout redds in the area. We found a total of only 20 redds in the 2 ½ mile lower spawning reach below Sand Hollow with none of the redds being in the proposed augmentation areas. For comparison in the riffle and run below the Hollywood Hole we there are 65 or more redds in a 100 yard riffle. Our depth and flow measurements have confirmed that our proposed augmentation sites are suitable locations to add gravel. Having these measurements not only validate that the sites are good but gives us supporting evidence that we can use to apply for a grant from the Oregon Department of Fish and Wildlife to help fund the gravel augmentation. We are working on the grant and permit paperwork now and if all goes well, we will be doing the gravel augmentation in November 2022. Stay tuned for more information and opportunities to volunteer to help.

This article first ran in the Hackle Bender club newsletter. Check out our old Hackle Benders!