Salmon spawning and water quality surveys in Auburn Ravine are complete: Hemphill project is moving forward

October 17, 2019

Chinook salmon redd

An important fish and water quality study is complete, and NID is moving ahead to find a solution to increase habitat for native anadromous species in Auburn Ravine Creek.

The focus is on the Hemphill Canal diversion point on Auburn Ravine Creek upstream from Lincoln. Built in 1935, canal diverts water for use in NID’s Placer County water distribution system. However, the diversion facility can act as a partial barrier to upstream fish passage.

NID has been working for a few years to find an alternative, including the removal of the diversion facility, to improve Chinook salmon and steelhead trout passage, spawning and juvenile rearing in Auburn Ravine. In 2017 the District received a $177,000 grant from the California Department of Fish and Wildlife to complete fish and water quality surveys to assist in the evaluation of options.

The surveys focused on two major areas through two migratory seasons; 1) collection of water quality data to determine whether water quality is suitable for salmonid migration and egg incubation, and 2) collection of spawner abundance and distribution data, including live adult Chinook salmon and redds (egg nests).

In summary: six adult Chinook salmon were observed in 2017 along with one redd, and no Chinook salmon adults or redds were observed during the 2018 surveys in Auburn Ravine. Juvenile and adult rainbow trout (Oncorhynchus mykiss), as well as Sacramento sucker (Cotostomus occidentalis occidentalis) and Sacramento pikeminnow (Ptychocheilus grandis) were observed during all surveys throughout Auburn Ravine and often in abundance, further alluding to the suitability of water quality conditions in Auburn Ravine for fish production.

The surveys were reviewed and discussed during NID’s Oct. 15 Engineering Committee meeting. The next step is to complete a California Environmental Quality Act (CEQA) document. NID is excited to move this project ahead, and to further our commitment to supplying connectivity within the stream system.

Hemphill diversion structure

The Hemphill Diversion Facility is an approximately 8-foot-tall, concrete structure located in Auburn Ravine. Historically, the structure has been fitted with 3-foot-tall flashboards during irrigation season (April to October) to increase the water surface elevation upstream and direct flow into the Hemphill Canal.

The facility is located three miles upstream from a $1.2 million fish ladder below Highway 65 completed by NID and project partners in 2011. That project has contributed to fish migration in Auburn Ravine.

Read the 2017-2018 Salmon Spawning and Water Quality Surveys. Click here.