This habitat improvement project is timely. Low flows and high water temperatures have made 2021 a dismal year for salmon and steelhead in California. Hemphill Dam is blocking access to prime spawning habitat, and its removal will benefit migratory fishes, especially in hot, dry years like this one.
“The Hemphill Dam passage improvements will greatly improve Auburn Ravine for spawning and rearing by native fishes. It is a good example of improvements needed to benefit native fish populations at hundreds of locations across the state,” said Peter Moyle, a UC Distinguished Professor Emeritus and advisor to Water Audit.
Hemphill Dam is an eight-foot tall barrier that diverts water flowing through Auburn Ravine into a canal serving Turkey Creek Golf Club and the Sun City Lincoln Hills residential community. Further downstream the Ravine provides water to the rice farms west of California Highway 36.
On July 28, the NID’s Board of Directors approved removal of the existing structure and the construction of a nature-like rock ramp within the stream channel that will allow fish to swim upstream to spawn. A fish screen will be installed on the canal intake to prevent fish and lampreys from entering.
The upstream crest elevation of the ramp will be two feet lower than the existing dam crest. “The rock ramp structure would provide fish passage while also improving sediment continuity over the dam and likely improving bank stability upstream of the dam,” according to NID’s Environmental Impact Report.
A 2011 NID study reported that the area upstream of Hemphill Dam in Auburn Ravine is the best potential salmonid spawning habitat in all of Placer County. Restoring fish passage will benefit Threatened Central Valley steelhead and spring-run Chinook, as well as fall-run Chinook, a Species of Special Concern, without any impairment of the existing water deliveries.
“The Auburn Ravine is important for juvenile fall-run Chinook salmon that are emigrating from the upper reaches on their journey to the Pacific Ocean via the Sacramento River during winter and spring months. The Auburn Ravine also appears to provide rearing habitat for non-natal rearing of juvenile winter and spring-run Chinook salmon,” said California Department of Fish and Wildlife in a 2015 memorandum.
In December of 2019, Water Audit California commenced a legal action alleging that the NID’s facility created an unlawful stream obstruction. In January 2020 Water Audit and NID entered into a settlement agreement that provided a final EIR would be published by April 1, 2021, and that this adoption of a plan would follow. It is anticipated that construction will be part of NID’s 2022 budget.
NID’s recent action is the near-culmination of a 20-year process. Citizen advocates and regulatory agencies including NOAA Fisheries, California Department of Fish and Wildlife, Friends of the Auburn Ravine, and Save Auburn Ravine Salmon and Steelhead all contributed to this success.