Most data shown here are from the USGS via the waterservices site, plus the USBR and CDWR via the California Data Exchange. Data are provisional and may be recalculated before final approval. The TRRP site checks for new sub-daily values every 15 minutes and for new daily values twice per day. Note that “Full Natural Flow” is an automated estimate from CDWR of the flow that would naturally pass the Trinity Dam site if unimpeded – it is very sensitive to small variations in lake level measurements that may result in negative values when flows would naturally be low, but is more useful for storm events, snowmelt, and averages over longer times. The graphic for water released to the Trinity River versus the water diverted to the Central Valley tends to show higher values for the river until summer, when water exports to the Central Valley typically increase. Click here for a summary of Trinity River flow volumes.
Snow Melt Peak and Recession Period (Apr. 15 – Aug. 17 )
The California Department of Water Resources has posted the 2025 Water Year B120 50% Exceedance Forecast as “Wet” with a predicted inflow of 1,880,000 acre feet into Trinity Reservoir.
The “wet” water year declaration allocates 701,000 acre feet of Trinity Reservoir water for restoration purposes.
For the 2025 spring release, flows will peak at 8,500 cubic feet per second at noon on Apr. 16. After the peak a slow recession begins at 6 p.m, reaching 600 cubic feet per second on Jun. 30. Flows are scheduled to minimally rise again for two small peaks on Jul. 11 and again on Aug. 2 to help salmon migrate out of the lower portion of the river.
The hydrograph developed by the Program with the “wet” water allocation for Mar. 15 – April 14 will commence on March 21 after Storage Management Releases from Trinity Reservoir come to a close.
The hydrograph developed by the Program with the “normal” water allocation did not exceed Trinity Reservoir Storage Management releases which ranged from 1500 cfs to 3500 cfs and are anticipated for the remainder of February and into March due to significantly encroached levels per the safety of dam criteria. For water accounting, the Program will deduct 60,000 acre feet from Reclamation flows during this period (Feb. 15 – Mar. 14), thus saving the reservoir valuable storage in the summer months.
Synchronized Flow Period(Dec. 15 – Feb. 14)
A synchronization flow was triggered on Dec. 20 for a peak on Dec. 24 and 25. Flows were scheduled to ramp down to winter baseflow (300 cfs) on Jan. 11. However, on Dec. 31 the Bureau of Reclamation’s Central Valley Operations Office released a change order for flows from Trinity and Lewiston Dams for storage capacity concerns in Trinity Reservoir. Due to a combination of low water diversions in 2024, the continued maintenance and closure of the Clear Creek Tunnel, in combination with recent precipitation, current storage in Trinity Reservoir required the release of additional flow to the Trinity River to absorb for future winter storms.
Ways to Stay Informed
This Trinity River flow release notification group is utilized to inform the public about both flow releases and releases to the river for other purposes from Lewiston Dam.
The California Nevada River Forecast Center shows forecasted river levels five days into the future. When a storm is predicted to raise flows to 4500 cfs at the North Fork gauge this initiates a trigger to request a synchronized flow of up to 6500 cfs from Lewiston Dam.
If you have questions, please contact the Trinity River Restoration Program office at 530/623-1800 or by emailing your question to info@trrp.net.
WY2025 Changes to Flow Management
With support from the Hoopa Valley and Yurok Tribes, the Bureau of Reclamation announced approval of changes to the timing of water releases from Lewiston Dam into the Trinity River in December.
Reclamation, the Hoopa Valley Tribe, and the Yurok Tribe signed a Finding of No Significant Impact for the Trinity River Variable Flow Project Environmental Assessment following on the recommendation from the Trinity River Restoration Program’s Trinity Management Council.
The Trinity River Variable Flow Project Environmental Assessment recommends a synchronized flow release and an increase to baseflows during the wet season. Managing environmental flow is important for improving food sources and habitat for Trinity River salmonids, like salmon and steelhead.
The implementation window for the first period of approved changes (the synchronized storm pulse period) begins Sunday, Dec. 15, 2024.
Synchronized Flow Period(Dec. 15 – Feb. 14)
One potential synchronized dam release during a specific period that is determined (or triggered) by a winter storm event.
The purpose of a synchronized flow action is to use flows to maintain and form river complexity. In addition to provide ecologically beneficial timing of riverbed turnover, by combining dam releases with a storm event, flows aim to reduce the impact of sedimentation on salmon redds deposited from tributaries like Deadwood Creek.
Wet-Season Baseflow Period (Feb. 15 – Apr. 14)
An increase to prescribed Record of Decision dam releases during a specific period determined by a conservative monthly inflow projection for Trinity Reservoir from the California Department of Water Resources (90% B120).
The purpose of adaptively managing river flows is to increase available food sources and habitat for juvenile salmonids while rearing (growing) in freshwater, prior to their migration to the ocean.
Snow Melt Peak and Recession Period (Apr. 15 – variable)
In April, the Program plans to implement spring snow melt releases with remaining available water based on the California Department of Water Resources April 2025 water year determination.
