TRRP: Water Year 2025 (Oct. 15

Water Year 25 thus far has been a good year for Trinity Reservoir. In October, Trinity Reservoir measured in at 70% full with 1.7 million acre feet. Seasonal storms have recently pushed storage over 2 million acre feet (or 84%). In December, flows were held steady at 1500 cfs through January and increased to 3500 cfs after several atmospheric river systems passed through in early February.

Trinity Reservoir December 2024 [Kiana Abel, Trinity River Restoration Program]

Feb. Forecast – California-Nevada River Forecast Center

The volume of environmental flow releases for the Trinity River Restoration Program’s Wet-Season Baseflow Period (Feb. 15-Apr. 14) are determined by a conservative monthly inflow projection for Trinity Reservoir from the California Department of Water Resources (90% B120) in February, March with the final determination in April.

Prior to the official determination, which is published around the 10th of the month, water managers follow the California-Nevada River Forecast Center Median forecast for Trinity Lake inflow to stay abreast of the water year projections thus far.

The graph (shown in screen shot above) can be a little daunting to read, but when armed with the appropriate information is discernable for any viewer.

The Program’s Water-Year Volume Allocation as specified by the Record of Decision is outlined in the table below. The far left column is the threshold amount of state forecasted inflow in the Trinity Reservoir listed in acre feet which determines the center column, water year type. Then in the right column is listed the allocation to restoration for that water year, which includes baseflows.

Return now to an enlargement of the CNRFC forecast screenshot from Feb 12. Check out the light grey box “WY Vol Fcst 10/90%: 2,190/1,490 kaf” which reads longform as the following;

As of Feb. 12, the 10% of probability for Trinity Lake Inflow is predicted as 2,190,000 acre feet and the 90% of probability is 1,490,000 acre feet. Translated there is a 10% probability that the Trinity Allocation is predicted as “Wet” and a 90% probability is also “Wet”.

As managers track the predicted inflow via CNRFC, the Program’s Flow Workgroup develops hydrograph scenarios to use when the final determination is published by the California Department of Water Resources. The two agencies use different methods when it comes to these prediction tools, the California Department of Water Resources uses data that has a weighted average to compute statewide Snow Water Equivalent (SWE) and is known as a more conservative forecast method when comparing the two.

Wet-Season Baseflow Period (Feb. 15 – Apr. 14)

The next period within the Trinity River Restoration Program environmental flow management is the Wet-Season Baseflow Period, which initiates Feb. 15. The California Department of Water Resources February 90% B120 declaration was published on Feb. 11 as “normal” with the 90% determination at 1,295,000 acre feet.

The hydrograph developed by the Program with the “normal” water allocation does not exceed the current Trinity Reservoir dam releases which have ranged from 1500 cfs to 3500 cfs and are anticipated for the remainder of February because the reservoir is significantly encroached 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.

Red dotted lines indicate 1500 cfs and 3500 cfs while the black line indicates the developed hydrograph for the “normal” February B-120 declaration.

With the river at levels above 300 cfs there are benefits to Trinity River salmonids as wetted areas are providing additional areas to biology within the system. Any reduction in flows would inhibit or halt such production in areas wetted by current flows.

Of course, unexpected flows always come as a shock. This water year has been unique in that maintenance on Clear Creek tunnel has initiated the need to send storage management releases down the Trinity versus to Whiskeytown Reservoir. To remain prepared, river enthusiasts should expect changing flows authorized by Reclamation through the month of March.

Prior to the next period (Apr. 15 – variable), the Program has a check-in on Mar. 15 to adjust flows to the March 90% B120 declaration. In April, the Program implements it’s spring snow-melt and recession hydrograph following the final B120 water year determination by the Department of Water Resources.

Return to the Feb. Newsletter

Common names: Grey pine (most common), ghost pine, foothill pine, Sabine pine, bull pine or grey leaf pine.

Adapted to the long, hot, dry summers of our Mediterranean climate, the grey pine is endemic to California and prolificates within the ring of foothills that surround California’s Central Valley. It fairs well in rocky well-drained soils yet also grows in heavy, poorly drained clay soils. The species commonly occurs with Blue Oak (Quercus douglasii) which creates a unique partnership that is described as “Oak/Foothill Pine vegetation” and is indicative of the grey pine which provides a sparse overstory above the canopy of an oak woodland. The partnership in itself is the preferred habitat to black-tailed deer, California quail, as well as mourning dove and describes a characteristic within the California chaparral and woodlands ecoregion, of which Trinity County is part [1].

Photo published on The Gymnosperm Database. A tree at the Rancho Santa Ana Botanical Garden, California [C.J. Earle, 2004.04.13].

The grey pine is easily identifiable with pale grey-green needles that are sparse and a bit droopy. When looking from afar a grey pine is easily spotted by his smoky, wistful coloration. The structure of P. sabiniana tends to be a bit scrappy with its center trunk splitting sometimes several times, often bending every which way, versus holding a typical stature. Also easily identifiable are the seed cones which are among the largest produced by any pine species, when fresh weighing on average between 1-1.5 pounds. One particular source noted that, “The large, heavy cones resemble footballs covered with wooden spikes. It is best to avoid the pine groves on windy days.” [2] The cones tend to be full of sticky sap and are also home to a plethora of nutritious seeds enjoyed by many animal species, such as Steller’s jay, the scrub jay, grey squirrels and humans. The seeds have an impressive percentage of calories in the form of protein, fat and carbohydrates and provide several essential minerals to those who forage it [3].

This species is the principal host for the dwarf mistletoe Arceuthobium occidentale a perennial parasitic herb that is native to California [2]. Dwarf mistletoe is considered a disease that the tree can succumb to typically causing reduced tree vigor or death. If you have grey pines near your structures and the parasite is left uncontrolled, infection can increase sixty-fold within a window of 10 years [3].

Photo of dwarf mistletoe originally posted in the CalPhotos Database. Zoya Akulova 2008.

John Muir, describes this tree in the first chapter of My First Summer in the Sierra: “June 4. … This day has been as hot and dusty as the first, leading over gently sloping brown hills, with mostly the same vegetation, excepting the strange-looking Sabine pine (Pinus sabiniana), which here forms small groves or is scattered among the blue oaks. The trunk divides at a height of fifteen or twenty feet into two or more stems, outleaning or nearly upright, with many straggling branches and long gray needles, casting but little shade. In general appearance this tree looks more like a palm than a pine. The cones are about six or seven inches long, about five in diameter, very heavy, and last long after they fall, so that the ground beneath the trees is covered with them. They make fine resiny, light-giving camp-fires, next to ears of Indian corn the most beautiful fuel I’ve ever seen.”[2]

Photo published on The Gymnosperm Database. Small stand in the southern Santa Lucia Range, California [C.J. Earle, 2007.03.01].

The ethnobotanical uses of the grey pine are impressive with uses ranging from cultural to functional to nutritional. Although there are documented uses for all parts of the tree from sap to needle, primarily the seed gets the most attention. Seeds are noted to be gathered fresh, as well as roasted, boiled or pounded for porridge [5]. The hull of the seed is also used as a bead to decorate traditional dresses used for ceremony. Follow this link to read the lengthy, impressive list of all documented uses.

Photo published on The Gymnosperm Database. Ripe cone *in situ*; Bodfish area, California [C.J. Earle, 2014.01.17].

References & Further Reading

Return to the August Newsletter

Category Archives: Uncategorized

Water Year 2025 (Oct. 15 – Apr. 15)

Grey Pine (Pinus sabiniana)

References & Further Reading