Hemphill Dam Improvement Project
Before
After
Before
Before:
For almost 100 years, this dam blocked almost all salmon that swam up Auburn Ravine to spawn. In wet years, only 7 to 10 percent
were able to get over the dam to reach good spawning areas upstream. In years with less rain, none made it.
LETTER TO NEVADA IRRIGATION DISTRICT (NID)
When implemented, the Hemphill Dam Improvement Project will potentially remove an anadromous fish migration barrier on Auburn Ravine that will allow access to 6 miles of headwaters habitat that is further enhanced by seasonal instream water augmentation flows by Nevada Irrigation District.
Executive Summary/Abstract
Auburn Ravine is an important anadromous salmonid tributary to the Sacramento River, at the foothills of the Sierra Nevada. This project is Phase 2 in Nevada lrrigation District’s ongoing efforts to support re-establishment of connectivity within this stream. Hemphill Diversion has been identified as a partial salmonid migration barrier on Auburn Ravine, and lies 3 miles upstream of a fish passage project NID successfully completed in 2011. This project proposes to undertake the necessary assessments, including sediment, hydraulic, and fisheries studies, to inform NID’S ongoing efforts to develop alternatives for this site. We will also collect baseline water quality data about the site and identify all necessary permits associated with future implementation. By undertaking this planning effort immediately, NID will continue to advance the project schedule as we have already completed an options analysis for the Hemphill Diversion in 2016.
The intent of this project is to evaluate options and support an inter-disciplinary process by a Technical Advisory Group in NID’S selection of preferred option, and to inform an Environmental lmpact Report (ElR) that will be undertaken by the NID in the future. The proposed tasks will be initiated in 2017 and completed in 2020, and all relevant partners are poised to assist in the successful completion of these tasks. Auburn Ravine is part of a network of smaller tributary streams to the Feather River, and subsequently the Sacramento River, in the Northern Sierra Nevada Diversity Group as established in the central valley steelhead Draft Recover Plan, NMFS. ln restoration plans and recovery documents, federal, state and regional agencies have identified Auburn Ravine as having significant fish resources, and with the potential to support higher levels of production after an ecosystem restoration program such as this is implemented.
The preceding is copied from the Auburn Ravine-Hemphill Diversion Assessment Project Narrative with permission from the Nevada lrrigation District.
See more about the project on their website >>>
Hemphill Dam during a recent irrigation season (April 15 to October 15). After the steel and wood structure was removed in mid-October, it still blocked most fish that tried to get over it.
After:
The Hemphill Dam along Auburn Ravine has been removed. Salmon can now access 4 times more spawning area than they have for decades.
The salmon now have access to about eight miles of streambed. And they are using it!
The dam was replaced by a modern water diversion system that allows salmon to migrate upstream with ease while also allowing irrigation water delivery via the Hemphill Canal to continue. The new system is called a Roughened Rock Ramp. It was installed in the streambed where the old dam used to be. It provides a gentle slope for the fish to swim up, and at its upper end it keeps the water high enough that water can still flow into the Hemphill Canal during irrigation season. A screen at the entrance to the canal keeps juvenile fish out of the canal so they can continue their trip down to the ocean. To keep water flowing to customers along the Hemphill Canal, the screen is designed with mechanical wipers to keep itself free of leaves, sticks, other debris, and sediment that might clog it up.
The project was managed by Nevada Irrigation District (Headquartered in Nevada County, CA) and Westcon Construction of
Newcastle, CA. They completed the project before the first big rains came in the fall of 2022. When the rains came, and the creek
water rose, salmon began swimming up into Auburn Ravine from the Sacramento River. In early November, we started seeing them on
the Salmon Cameras that we operate near downtown Lincoln.
To find out where those salmon went, our volunteers conducted wading/walking surveys along many sections of the creek. Based on
those observations, we can say that the Hemphill Fish Passage Project is clearly a success!
Before the dam was removed, no more than 10% of the salmon that tried to get past the dam succeeded. Now that the dam is gone,
90+% of them are getting past the old dam site, significantly improving the likelihood of Salmon population growth!
In this photo, the old dam has been removed and replaced with a “nature-like” system. The concrete walls of the canal intake can be seen in the distance just to the right of center.
(Friends of Auburn Ravine Photo.)