U.S. Fish & Wildlife Service

Lodi Fish & Wildlife OfficeServing the people and conserving the fish, wildlife and plants of California

A Unit Of The Pacific Southwest Region

Instream Flow

What is Instream Flow?

In 1995, the Sacramento Fish and Wildlife Office began a series of studies to identify the instream flow requirements for anadromous fish within the Central Valley of California.

Photo of a habitat sampling site

Instream Flow Habitat Sampling Site
FWS Photo

With funding from the Central Valley Project Improvement Act, instream flow studies have been completed on the Sacramento, American, Yuba and Merced Rivers and Butte Creek, and are in progress for the Stanislaus River and Clear and South Cow Creeks.

In 1999, the Sacramento Office began additional studies to evaluate the effectiveness of restoration projects on Clear Creek and the Merced River. These efforts were expanded in 2009 to provide scientific information to other Central Valley Project Improvement Act programs for use in assessing fisheries restoration actions.

These actions included fish screens at Red Bluff, gravel additions on the American River, and Central Valley Project Improvement Act dedicated water used to reduce redd dewatering on the Sacramento and American Rivers and Clear Creek

The ability of a fish to spawn and rear young to survive is dependent on the volume of water flowing within the creeks and rivers. Too little flow at critical times could cause salmon eggs and young to become stranded and die. Too much water and the eggs and young can be washed away during a flood situation.

At present, our staff are:

macroinvertebrate processing

SCUBA diving to collect deep water
juvenile habitat suitability data
FWS Photo

  • Collecting pre-restoration monitoring data to determine the amount of spawning and rearing habitat for anadromous salmonids created by the restoration projects for both the Bobcat Flat site on the Tuolumne River and the River Bend gravel addition project on the American River.
  • Habitat assessment on the North Fork of Cottonwood Creek
  • Collecting geomorphic monitoring data to use in the design of a restoration project on the Stanislaus River
  • Conducting as-built surveys and post-restoration monitoring for the Honolulu Bar restoration project.
  • Development of a two-dimensional hydraulic model to quantify the relationship between floodplain inundation and flow for the Stanislaus River.
  • Continuation of redd dewatering monitoring on the American and Sacramento Rivers that began in 2009 to evaluate the benefits of using Central Valley Project dedicated water to prevent redd dewatering on these streams.

Last updated: August 27, 2020