TRRP has received approval to continue Environmental Flow releases from Lewiston Dam for a second year (under the “Winter Flow Project”). All flows scheduled for release by TRRP must match the volume allotted for the water year (see Typical Releases), although the U.S. Bureau of Reclamation may release additional water for other purposes.
TRRP Environmental Flows currently include:
- A possible flow up to 6500 cfs at Lewiston, synchronized with a storm event between December 15th and February 15th. This would be triggered by a storm that is expected to make flows in the river rise to 4500 cfs or more at the streamgage above the North Fork Trinity River. Forecasts are only for 5 days, so this would be scheduled quickly. Triggering flows are expected to occur about one out of three years on average.
- Increasing baseflows from February 15 through April 15.
- A spring restoration flow similar to prior years but with reduced total water use.
- Baseflows (minimum flows) remain unchanged for summer (450 cfs) and winter (300 cfs) with the usual transition occurring on October 16th.
This page will be updated as flow schedules are approved. The chart below provides a red line for what has been scheduled thus far for the water year. This line will start with just the autumn, and will be continued as the year progresses and we have more knowledge of the storms to come and the quantities of water that will be available. The blue line will show what has actually been measured at the Lewiston gage. Flows in gray (filled below) show an automated estimate of what natural flows past Lewiston Dam would have been. Background colors indicate the approximate flow possibilities for different time periods.
Realtime Flow Chart
Graph below may take a minute to load.
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.
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.
The Trinity River Restoration Program Facebook page is a great place to stay informed of Program activities.
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.