The Trinity River is enjoying a renaissance with California’s steelhead fishermen, and while steelhead populations seem to be prospering, salmon populations remain a bigger question.
In this piece, CalTrout’s North Coast manager Darren Mierau looks at the Trinity’s recent history and (maybe) comeback.
By Darren Mierau
More than a decade has passed since the Trinity River Record of Decision (ROD) was signed in December 2000 by Bruce Babbitt, then Secretary of the Interior under President Clinton. Since then, there has been uncertainty about what has been done and the effectiveness of the work on the Trinity.
A Little History
A brief reminder of the Trinity’s illustrious background may be useful to set the stage.
At 2,900 square miles, the Trinity River is the largest – and arguably the most important – tributary to the Klamath River, joining the Klamath 45 miles upstream of the Pacific Ocean.
Historically, the Trinity River and its tributaries provided many hundreds of miles of salmonid habitat, and supported robust runs of spring and fall-run Chinook salmon, winter and summer steelhead, coho salmon, coastal cutthroat trout, sturgeon, lamprey, and other native fish and wildlife species. The Trinity River Flow Evaluation Study (TRFE; USFWS 1999) estimated up to 75,500 fall-run Chinook returned to the Trinity in good years.
Up To 90% Of Flows Diverted
Construction of Lewiston Dam on the Trinity River was completed in 1964 and blocked salmon and steelhead access to over 100 miles of habitat above the dam. Water operations then began diverting up to 75-90% of the annual water yield at Lewiston over to the Sacramento River for agricultural uses in the Central Valley.
The dramatic reduction in flows below the dam had severe consequences for the river channel and salmonid populations. In addition to habitat loss upstream of the dam, the river’s spawning gravel supply was cut off, the river became confined by riparian berms, spawning gravels and pools became degraded by fine sediment, and low baseflow releases provided poor water temperature conditions during the spring smolt outmigration period.
In addition, water quality conditions in the lower Klamath River had deteriorated to the point where survival of Trinity River juvenile salmonids heading out to the ocean was probably very low in many recent years.
The Trinity River Record of Decision, and the Trinity River Restoration Program (TRRP) built upon it, are intended to reverse degraded river conditions and bring back robust salmon and steelhead runs. But how does the TRRP propose to accomplish recovery. Casting aside the past paradigm of single-species management, the TRRP pursues recovery through several important program components:
- Streamflow management to re-establish the natural, physical processes (annual flood flows, gravel supply and transport, bank scour and floodplain inundation, plant desiccation, etc.) that create and maintain high quality aquatic habitat
- Mechanical reconstruction of channel banks and floodplains to rescale the river to fit the post ROD flow regime
- Sediment management to increase beneficial coarse-sized spawning gravels and reduce detrimental fine sediment
- A rigorous science and adaptive management program to learn from this fundamentally important experiment in river restoration.
To date, the TRRP has accomplished the following:
- All of the infrastructure upgrades (bridge replacements, road work) have been completed to allow Lewiston Dam high flow releases up to a maximum of 11,000 cfs
- The ROD recommended flow regime has been fully implemented since 2005, with the first-time peak of 11,000 cfs released from Lewiston for three days in May of 2011
- The sediment augmentation program has placed approximately 65,000 cubic yards of coarse gravel and cobble to recreate spawning habitat and other river features
- A total of 23 bank rehabilitation sites have been built in Phase 1 of mechanical reconstruction, and another 23 sites are planned and designed for Phase 2.
So, how are these accomplishments impacting the salmon and steelhead returns?
Two fish trapping weirs are operating on the Trinity River, one near Willow Creek (for enumerating fall-run Chinook, coho, and fall-run steelhead) and one near Junction City (for enumerating spring-run Chinook). Fish returning to the Trinity River Hatchery are also counted.
Estimates of the total run size of fall-run Chinook salmon upstream of the Willow Creek weir show annual returns to the Trinity River in recent years to be fluctuating in a range typical of the past three decades – with run-size estimates ranging between 23,000 and 64,000 fish. No post-ROD rebound in adult Chinook counts appears in the data, but Chinook seem to be holding steady.
Coho salmon, on the other hand, appear to be declining further in the Trinity River, despite being supported by a hatchery. Similar declines are being observed in many other rivers throughout the North Coast. Following several good years in which adult coho estimates exceeded 20,000 fish, the past four years have not topped 10,000 adult coho, and have dipped as low as 5,750 adult coho.
Steelhead, the elusive salmonid that defies our best efforts at population estimation, appear to be doing well in the Trinity River, and maybe better than the salmon runs.
As of early October 2011, DFG biologists reported seeing “large numbers of steelhead pass through Willow Creek [weir] and have surpassed the number trapped there all of last year.” They also noted “a large percentage of Chinook salmon are two year old jacks (grilse). This potentially bodes well for next year’s run, particularly the three year old adult component.”
A fish rebound may not be entirely clear from available data, but some program participants think even this year may be the first clear uptick, and the next few years may continue to see larger salmon and steelhead returns.
So, while the outcome of the TRRP is unclear, one thing is certain – the past decade has brought tremendous change to the Trinity River. And more change is certain to come.
CalTrout will continue to support the ROD and the river restoration program. We also encourage program managers to conduct a thorough review of Phase 1 implementation, and to respond to concerns voiced from outside the program on the outcome of restoration actions.