Stewart Lake is the most important nursery habitat in the upper Colorado River system for two species of listed fishes, the Razorback Sucker and the Bonytail. Since 2012, UDWR has operated Stewart Lake in cooperation with the USBOR under the Larval Trigger Study Plan. To accomplish this, we have made various improvised changes and alterations to the existing outlet works in place for selenium mitigation. Although we have had remarkable success with the project, the existing infrastructure is less than optimal and causes multiple safety concerns during operation. An engineered plan and cost estimate for needed improvements will give us the tools needed to seek funding.

Obtain an engineered plan and cost estimate for a new water control gate (split gate design), a new slanted fish exclusion screen, catwalks with railings around the fish excluding screen, a permanent ladder in the confined space between the gate and fish screen, a storage shed with cement pad, a jib crane, and a new fish trap design or alternate fish kettle system.

Our operations at Stewart Lake have been indispensable in facilitating natural reproduction and survival of both Razorback sucker and Bonytail. The recent proposed down-listing of Razorback Sucker from endangered to threatened was likely contingent upon demonstrated success of Razorback Suckers surviving beyond the larval stage at Stewart Lake. We have demonstrated the importance and effectiveness of our operations at Stewart Lake over the last 13 years. While the current infrastructure has sufficed for experimentation of wetland operations, we now need permanent, safe, and efficient tools to continue this proven management paradigm.

This will support the recovery plans for both Razorback Sucker and Bonytail as well as the Larval Trigger Study Plan and 2006 Record of Decision for Flaming Gorge Dam.

The proposed alterations to the control structure will improve the ability to fill the wetland during years with drought hydrology and limited periods of larval drift by replacing the fish excluding screen with one that is easier to clean and has greater surface area. Achieving a more complete fill with deeper water should have a small to moderate effect on cattail and bullrush growth in the center of the wetland, thus reducing fuels.

These improvements will allow us to entrain water into the wetland at a faster rate during the spring runoff and larval drift period, thus improving water quality later in the summer when low dissolved oxygen and elevated TDS often become an issue. Our endangered fish operations are conducted in accordance with an annual drain and fill cycle recommended for mitigation of selenium contamination that predates the Larval Trigger Study Plan. These improvements will help us continue this in a safe and efficient manner.

Most work will likely occur within the existing footprint of the control structure and levy. We will consult with the UDWR habitat section on the need to NEPA work if the engineered plan requires additional disturbance.

Hire an engineering firm experienced with water control structures, and/or fish traps or passages to develop a project plan and cost estimate.

Ongoing monitoring of fish use of Stewart Lake is conducted under recovery program project fr165.

Upper Colorado River Endangered Fish Recovery Program, US Fish and Wildlife Service, US Bureau of Reclamation

After completion, we will use the project plan and cost estimate to pursue recovery program/BOR capital funds or other grant opportunities to complete the project.

Recovery efforts for these species allow water development and dam operations to continue with compliance under the ESA.