Off to a good start
Precipitation at 378% of average for now, but rest of the year unknown
Rodney O’neal, 54, of Crystal Falls, and Frank Enos, 66, of Sonora, looked over the low waters in New Melones Reservoir on Tuesday morning and marveled at how little visual evidence there appeared to be of the record-breaking blockbuster storm that soaked the Central Sierra Nevada and most of Northern California on Sunday.
New Melones, the fourth-largest capacity reservoir in the Golden State, was still just 34% full on Tuesday, the exact same as it was three-and-a-half weeks ago, according to California Data Exchange Center numbers kept by the state Department of Water Resources.
“It came up a foot,” O’neal said optimistically. “I saw it on my phone. You can see the difference at the boat ramp, the third ramp at Tuttletown. We’ll take it. We need more.”
“We like this lake and we enjoy fishing here in the summer,” Enos said. “We’re glad it’s getting water and filling up.”
O’neal said he went to Yosemite Valley last weekend, before the big Sunday storm hit, and he’d never seen the Merced River so dry.
In spite of no visual proof of the Sunday whopper storm’s runoff at New Melones, a five-station index for Central Sierra watersheds, including the Stanislaus and Tuolumne rivers, showed a jump from less than 1 inch of precipitation last week to 6.6 inches as of Tuesday morning.
The current water year began Oct. 1, and 6.6 inches is 378% of average for the date Oct. 26. That 6.6 inches is also more than a third of the total annual precipitation the Central Sierra received for the entire water year that ended Sept. 30.
According to the state Department of Water Resources, water year 2020-21 was the third-driest on record in the Central Sierra, with just 18.8 inches of total precipitation. The water year 2019-20 was
also well below average, with 24.6 inches total.
The annual average on the state’s five-station index for Central Sierra watersheds is 39.9 inches, based on precipitation data from 1966 to 2015.
Although the current water year is off to a booming start, it will take a lot more storms this winter to make an average or above-average water year.
The last time the Central Sierra had an above average water year was 2018-19, with 50 inches of precipitation. The year before that was below average, though 2016-2017 was the second wettest water year on record at 72.7 inches of total precipitation.
Regardless of whether this winter brings enough storms to push Central Sierra precipitation and snowpack above average again, Dr. Michael Anderson, state climatologist for the California Department of Water Resources, says this winter is still expected to be characterized by La Niña conditions, which mean variability. The next two weeks are expected to be generally clear and dry in the Central Sierra.
“One storm this early in the water year does not predict the rest of the winter storm season,” Anderson said. “After this system we see a period of dry conditions return to California.”
The big storm Sunday was unusual for the month of October, Anderson said.
“The size of the storm was the major factor,” he said. “While in recent history, October storms are not that common. We do get October storms, and this one was rather large and classified as a Category 5 atmospheric river.”
Anderson called the Sunday storm “a historic storm by many measures, including many 24-hour accumulated precipitation records,” such as a new record for Sonora.
Sonora’s new 24-hour rain record for the date of Oct. 24 is 3.28 inches recorded Sunday at the Tuolumne Utilities District plant at Stockton Road and Highway 108. The previous record for the date was 1.9 inches in 1982.
The Sunday storm’s impacts on the ongoing drought were significant, Anderson said.
“Great storm,” he said. “In many areas the single day totals accounted for 50% to 80% of the entire total precipitation observed in the prior water year, articulating how dry it has been.”
Anderson said the Sunday storm and October precipitation to date already make up about 20% of what’s expected for an entire water year in the Northern Sierra.
While this is a great start to the water year and much needed, Anderson said it’s a reminder that the wettest months — historically, at least — are still to come. It will be “crucial that we get rain and snow in those months and throughout the year to really help end the drought,” he said.
Warming and dryness that have occurred over the past decade mean California is in a state of “climate water deficit,” Anderson said. The Golden State has had much less accumulated precipitation over the past few years than normal, and soils are so dry “we cannot fix this condition with one storm.”
Snow depths in the Central Sierra as a result of the Sunday storm were around 1 inch to 2 inches in most locations, with snow-water equivalents of 0.25-0.5 inches at best, Anderson said.
The bottom line, Anderson said, is that Sunday’s storm was historic in nature by its magnitude. But the Central Sierra will still need more than 30 additional inches of precipitation this winter to get to average this water year.
It would take more than 50 additional inches to get to 150% of average and help get the Central Sierra really get out of the drought.
Anderson underscored how dry it’s been and how far the Central Sierra is from truly being out of the ongoing drought when he said “in fact we’ll need closer to 200% of average in the Central and Southern Sierra.”
Two-hundred percent of average in the Central Sierra is 79.8 inches. The wettest water year on record for the region was 1982-1983 with 77.4 inches.
Dore Bietz, the Tuolumne County Office of Emergency Services coordinator, said there haven’t been any additional well failures locally since she last reported on Oct. 1 that 35 wells on about 15 properties in the county had dried up or were failing.
Fifteen of those wells were completely dry or failed, while the remaining 20 wells were described as struggling or not producing adequately. Eight families had requested emergency assistance, and four families were receiving bottled water.
The numbers are still the same,” Bietz said on Tuesday. “We will be surveying those we provide water assistance to this week, to see if they have seen a change in their well levels as a result of the latest storm.”