Charts show where California reservoir totals stand after the latest torrential rains


A recent new wave of heavy rain and snow after a dry November soaked a thirsty California landscape – but that was not enough to dramatically improve the state’s water storage levels, according to department data Californian water resources.

Even after the atmospheric storm on Sunday and Monday, in addition to a similar downpour in October, most reservoirs in northern California have changed little and remain below water levels of a year ago and above. historical averages, based on data.

Rain has raised the level of some reservoirs slightly – Lakes Mendocino, Shasta and Oroville all hold a little more water than last month, while others have remained the same.

But even though reservoirs did not see a significant increase in the near term, the weekend brought snow, including 5 feet across the Sierra. In the spring, that snow will melt into runoff, once again adding to the reservoirs, said Michael Anderson, state climatologist with the California Department of Water Resources.

The atmospheric October river fell mostly on dry soils, he said, meaning they absorbed much of the water, leaving little for runoff. But now that the ground has regained some of its moisture, when the snow from the cold December storm melts, less snow will be soaked in the ground and more will flow into the reservoirs.

There won’t be enough rain in a year to end the drought, Anderson said, but consistent, above-average rainfall “will at least mitigate some of the more serious consequences.”

“We may not be able to escape a record drought in a year, but we can at least be in a better place,” he said.

The key, he said, is a mix of hot and cold storms, like those in October and December respectively, which can replenish soil moisture and increase the snowpack during drier seasons.

The duration of this snowpack depends on whether January, February and March receive enough precipitation to maintain it. So far, the forecast still calls for a relatively dry season with more dry days than rainy days, Anderson said, but those wet days still have the potential to bring a lot of rain all at once.

“If we are lucky with atmospheric rivers on these wet days like last week, we could still reap benefits,” he said. “So there is still room for hope.”

Other large reservoirs around the state have seen a similar trend. While a few have received a boost with recent rain – although none is above 1% – almost all are below historic levels for this time of year.

An outlier is Hetch Hetchy, a major water source for the Bay Area. It has more water in December than last year, as well as more than its historical average. This can be attributed to the “conservative” operating practices of the reservoir managers, Anderson said.

“Each reservoir has its own operating criteria,” said Anderson, which, along with precipitation, affects the amount of water they contain.

But in general, “we want to see warmer storms that generate surface runoff so that we can recoup some storage loss, but we also want to see cooler storms coming in to make sure the snowpack is there for the future. spring, ”he said. noted.

More rain is on the way this month, Anderson noted, which, while far from anti-drought, is a good sign for him.

“We have to be aware that the outlook is for things to be quiet, but we will take what we can get and we will be happy that at least December has passed,” he said.

Danielle Echeverria is a writer for the San Francisco Chronicle. Email: [email protected] Twitter: @DanielleEchev


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