There are four basic types of flow releases to the Trinity River:
- Releases for River Restoration (including “base flows”)
- Klamath River Augmentation
- Ceremonial Purposes
- Reservoir Management
Information for each type of flow release is described below and past quantities are provided on our Flow Volume Summary page.
RELEASE FOR RIVER RESTORATION
The Trinity River Record of Decision (ROD) in 2000 increased the quantity of water allowed to flow down the river in order to maintain fish health (“base flows”) and provide variable flows for restoration of river ecology (“Restoration Flow Releases”). The ROD was designed toward exporting 52% of the water to the Central Valley Project, versus releasing 48% of the water to the Trinity River (these are long-term averages as reservoirs are meant to store water, filling in wet years for greater export during dry years). Flows to the river are to be recommended by the TRRP, thus volumes allotted to the river are known as “Restoration Volumes” even though they include the base flows of the river year-round. In order to achieve those percentages while enabling TRRP to schedule Restoration Flow Releases, the ROD specified volumes allotted to the river for 5 water year types, with the water year type to be determined by state forecasts of reservoir inflow (table below).
Water-Year Volume Allocation as Specified by the Record of Decision.
| State Forecast Inflow to Reservoir (acre-feet) | Water Year Type | Allocation to Restoration (including base flows) |
|---|---|---|
| > 2,000,000 | Extremely Wet | 815,000 |
| 1,350,000 – 1,999,999 | Wet | 701,000 |
| 1,025,000 – 1,349,999 | Normal | 647,000 |
| 650,000 – 1,024,999 | Dry | 453,000 |
| < 650,000 | Critically Dry | 369,000 |
One acre-foot is the volume of water one foot deep in the area of one acre.
A water year is defined as October 1 through September 30.
TRRP uses these Restoration volumes toward Restoration Flow Releases that are designed to meet specific management objectives aimed at improving ecological function of the river. Each year, as the likely allocation of water becomes clear, scientists across the TRRP collaboratively develop one or more flow schedules (hydrographs) and forward them to our Trinity Management Council (TMC) for formal recommendation to the U.S. Department of Interior. Once the Regional Directors from Reclamation and U.S. Fish and Wildlife Service approve a flow schedule, Reclamation implements the flows with Secretary approval. TRRP has no option to store allocated water from one year to the next. This process is further discussed on our Current Restoration Flow Release page.
KLAMATH RIVER AUGMENTATION
The Bureau of Reclamation sometimes increases the release of Trinity water via Lewiston Dam to the Trinity River to mitigate late summer conditions in the lower Klamath River for fish health purposes. The Bureau of Reclamation coordinates these releases with the Trinity River Restoration Program and usually provides several weeks public notice. Such releases are independent from the ROD releases for river restoration.
CEREMONIAL RELEASES
The Hoopa Valley Tribe requests that the Bureau of Reclamation increase releases of Trinity water via Lewiston Dam in odd-numbered years to support tribal ceremonies. These releases typically span only a few days and often form a small peak over the Klamath River augmentation flows. The Bureau of Reclamation also coordinates these releases with the Trinity River Restoration Program and usually provides several weeks public notice. These releases are independent from the ROD releases for river restoration.
RESERVOIR MANAGEMENT RELEASES
The Bureau of Reclamation may occasionally need to release water from Trinity Lake in order to protect or maintain infrastructure within the Trinity River Division. These releases may be triggered for a variety of reasons ranging from dam safety to maintenance of power generation equipment. While these releases often occur in relation to winter storm events, releases were increased during a 2018 wildfire event. Reservoir management releases are scheduled by the Bureau of Reclamation in response to current conditions and sometimes have little advance warning. These releases are made independently from the ROD releases for river restoration.
RESTORATION FLOW PAGES
Current Restoration Flow Release Schedule