Trinity River

Background

In 1959, the County of Humboldt and the United States Department of the Interior – Bureau of Reclamation entered into a contract for annual water releases of not less than 50,000 acre-feet from Trinity Reservoir into the Trinity River. The Trinity River Division of the Central Valley Project, operated by the Bureau of Reclamation, diverts nearly half the stored water in Trinity Reservoir to the Sacramento River. In 2014, the Department of Interior Solicitor issued an opinion memo affirming the Bureau of Reclamation’s obligation to fulfill its obligations under the contract with Humboldt County. However, the Bureau of Reclamation has not made releases in response to the County’s calls for water, citing the need for additional information and regulatory compliance actions.

Water Management Plan: Supplemental Fisheries Releases (December 2023)

In 2021, the California Wildlife Conservation Board approved a funding allocation to Humboldt County through the Stream Flow Enhancement Program to develop a water management plan for utilization of Humboldt County’s Trinity River contract water to benefit fisheries through increased in-stream flows (non-consumptive beneficial use). The project was designed to engage stakeholders, perform technical analysis and modeling, and develop a plan to guide decision-making over a 25-year planning period. Technical studies identified needs and priorities for releasing additional water from Trinity Reservoir into the Trinity River to help restore natural processes and improve fisheries. These releases will be in addition to the volumes released by the Trinity River Restoration Program [https://www.trrp.net/]. 

The main elements of the plan include: 

  1. Release of supplemental baseflows (approximately 36,000 acre-feet) from October through February in all years; 
  2. Release of supplemental fall pulse flows (approximately 14,000 acre-feet) from October through December in most years; and 
  3. Release of supplemental baseflows (up to 17,000 acre-feet) from February through April in some years.  

The modeled beneficial effects on Chinook salmon populations were primarily due to increases in habitat area during the spawning life stage in October through December (which decreased redd superimposition and improved egg survival) or increases in flow during the fry emergence and juvenile rearing life stage in March through April (which increased the fry and parr carrying capacity of individual habitat units).  The proposed releases would also have many non-modeled benefits to Chinook and coho salmon. Improvements to salmonid populations would have direct economic benefits to Humboldt County, Tribes, and surrounding areas and other important social, cultural, recreational, and tribal benefits.  

This plan for initial use of Humboldt County’s contract water does not preclude future consumptive uses or alternative future non-consumptive uses.

The final plan is here: Humboldt County Water Management Plan for Trinity River Contract Water: Supplemental Fisheries Releases (December 2023)

Reports and Documents

1959 Water Contract, Humboldt County and BOR

Solicitor’s Memorandum M-37030 (December 23, 2014)

Baseline Conditions Report (Stantec Consulting Services, November 1, 2022)

Modeling Report – Hydrologic, Water Operations, Reservoir Temperature, River Temperature, Sediment Transport, Habitat, and Fish Population Modeling for the Trinity River Water Management Plan (Stantec Consulting Services, August 2023 with contributions from U.S. Geologic Survey, Western Fisheries Research Center and U.S. Fish and Wildlife Service, Arcata Fish and Wildlife Office)

Letter from Humboldt County to Bureau of Reclamation (Humboldt County, June 23, 2023)