As the sun returned to expose bright white mountaintops around Trinity County, the talk of the town has been whether Trinity Lake could refill in 2023. Officials say it’s not likely, even though the recent rainstorms raised the lake significantly.
On Dec. 25, 2022, the lake was at its lowest for the year, at 2,188 feet elevation. Rain and snowfall have caused it to rise steeply, reaching 2,224 feet by Jan. 23, a difference of 36 feet. However, the difference between this year’s elevation and last year’s is less than a foot, and the lack of rainfall this week has caused the steep climb to taper off. It should also be noted that the elevation on Jan. 23 in 2021 was 56 feet higher than it is today.
The lake is considered full at 2,370 feet, meaning it still has 146 feet to rise until full, but as the lake rises, it covers more surface area, requiring increasing amounts of water for every foot in elevation reached.
While that would seem to indicate that the lake would need about four more similar rain episodes like the last one to fill, another factor comes into play and makes more of a difference — snow.
Much of Trinity Lake’s watershed, the area from which water drains into the lake, lies mostly in the Trinity Alps. Trinity Public Utility District officials say snow is a bigger factor than rain when it comes to filling the lake by summer. TPUD Manager Paul Hauser said last week that 80 to 90 percent of the lake’s summer water is melted snow.
Lake levels have peaked during April in previous years, but snowpack has been less than optimal. Snowpack levels are not yet available following the recent weather.
It’s been suggested that the lake would fill faster if the dam wasn’t releasing so much water to the ocean, but officials say that’s not really the issue.
Mike Dixon, Ph.D., the executive director of Trinity River Restoration Program, said the dam is releasing the minimum amount of water allowed during winter flows. He explained that since the Trinity Dam’s power plant was not designed to produce power at low constant flows, extra water will be released through the turbines to generate a pulse of electricity and then reduced for the rest of the day. He said that generating power requires that water be released from both Trinity and Lewiston lakes, it doesn’t have to happen at the same time. When a greater amount is released from Trinity in a short time, that amount can be drained from Lewison over a longer period.
“The reservoir will change a couple feet,” he said of the resulting depth, “but it really has no bearing on it.”
As for the potential to refill the lake to capacity this year, Dixon explained that while Shasta and Folsom lakes are nearly refilled, Trinity Lake takes much longer.
Trinity Lake is the third largest reservoir in the state but its watershed doesn’t produce as much,” he said, noting that Folsom Lake will fill in about a third the time it takes Trinity to fill. Dixon said a rule of thumb is that it takes three winters to fill the lake, although the estimate is a bit exaggerated.
With all that in mind, one should also consider that this winter follows three critically dry years in a row which left Trinity Lake at near-record low depths. Dixon said he’s received some water storage projections and with the mean inflow calculated, this year may see Trinity Lake fill to about halfway, at best.
“It’s going to take a lot more time to fill Trinity,” he said.
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