Turlock Irrigation District to begin spring pulse flows

Migratory salmon benefit from cool Tuolumne River water temp

On Saturday, April 16, 2022 California Central Valley-based Turlock Irrigation District (TID) expects to begin spring pulse flows in the Tuolumne River over the course of 10 days.

The 2022 spring pulse for the Tuolumne River will release roughly 14,000 acre-feet of water in total.

Pulse flows may cause river water levels to rise above the typical winter water levels and up to the flood plain on the north bank of the Tuolumne River between Dry Creek and the Highway 99 Bridge. (In this reach, the south bank of the river extends higher; it is not at risk of flooding.)

The Tuolumne River will not reach the flood stage due to the spring pulse flows.

A visible change in the river at 9th Street measurement station can typically be observed approximately 24 hours after the initiation of the pulse flow. A peak release of about 2,385 cubic feet per second (cfs) is anticipated. When the pulse flows reach 9th Street in Modesto, the river’s elevation will rise by approximately six feet.

Given multiple dry years, more exposure of the river bed and side banks has potentially attracted people and animals. The public is advised to be aware and exercise caution.

A “pulse flow” occurs when TID adjusts operations to release water down the lower Tuolumne River for the benefit of migratory salmon. The pulse flows cue migration by providing the fish with cold, oxygenated water and flushing out sediment and other debris accumulated during the year.

The district is required to provide the spring pulse flows as a condition of the license, under which it operates Don Pedro Project. Subsequently, TID works closely with fisheries agencies -– California Department of Fish and Wildlife (CDFW), U.S. Fish and Wildlife Service (USFWS), and National Marine Fisheries Service (NMFS) – in early spring to prescribe a spring pulse flow.

At the end of the pulse or pulse series, the majority of juvenile salmon have migrated out of the Tuolumne River into the Delta. Then, water flow is dropped down to pre-pulse levels and held steady through the summer to maximize efficient water management.