Don Pedro Reservoir

Don Pedro Reservoir on the Tuolumne River was 50% full Friday, according to the state Department of Water Resources, which issued a report summarizing the 2020-2021 water year that ended Thursday. Oct. 1, 2020 to Sept. 30, 2021 "was an extreme year in terms of temperature and precipitation," DWR staff said, and it followed the 2019-2020 water year that was likewise warm and dry. Statewide, the water year that just ended is the second-driest on record based on runoff, and the previous water year was the Golden State's fifth-driest on record.

The current ongoing two-year dry period in California, punctuated by the third-driest water year on record for the Central Sierra, is part of California’s overall arid fate so far in the 21st century, according to the state Department of Water Resources.

The Golden State’s hydrology now increasingly resembles conditions in the Colorado River Basin this century, where multiple, consecutive, drier-than-average years are mixed with an occasional wet year. California’s last wet water year was 2016-2017, the second-wettest on record.

The 2020-2021 water year that ended Thursday was an extreme 12 months in terms of warm temperatures and lack of precipitation, leading to the second-driest water year on record based on statewide runoff, the California Department of Water Resources said in a 12-page report titled “Water Year 2021: An Extreme Year.”

Precipitation monitors showed the Central Sierra ended the water year, which began Oct. 1, 2020, with 18.8 inches. That’s the third-driest on record for the region, Craig Shoemaker, climate program manager for the National Weather Service in Sacramento, said Friday. Central Sierra precipitation over the past water year — which began Oct. 1, 2020 and ended Thursday, Sept. 30 — was 46.7% of average.

The past 12 months were so dry that Sonora received just 15.73 inches of precipitation, 47.9% of normal, and it ranked as the fourth-driest water year on record for Sonora, Shoemaker said.

The 2020-2021 water year total is less than the 19 inches precipitation the Central Sierra received in 2014-15, the second-driest water year for the region on record.

State emergency proclamations for drought came out in April, May, and July, with 50 of the state’s 58 counties, including Calaveras and Tuolumne counties, declaring drought emergencies.

Also in Tuolumne County, 35 wells on about 15 properties had dried up or were failing as of Friday, another indicator of how the dry water year and the current drought’s effects are being felt in the Mother Lode. Fifteen of those wells are completely dry or failed, and the remaining 20 wells are described as “struggling” or not producing adequately, Dore Bietz, the county Office of Emergency Services coordinator, said Friday. Eight families have requested emergency assistance, and four families are currently receiving bottled water, Bietz said Friday.

Major reservoirs in the Mother Lode were also showing signs Friday of the drier than average water year that just ended. New Melones, the state’s fourth-largest capacity reservoir, was 35% full with dirt bathtub rings reaching high above the impounded Stanislaus River. Don Pedro, the state’s sixth-largest capacity reservoir, was 50% full, with a few powerboats in the low-lying waters of the Tuolumne River.

Tuolumne Utilities District staff said Pinecrest was holding 70% of capacity Friday, Lyons was holding 26% of capacity, and TUD was working with PG&E to bring more water from Pinecrest to Lyons.

“The start of the new water year, October 1st, is indicating a change in weather patterns,” Lisa Westbrook with TUD public affairs said Friday. “The National Weather Service is predicting above normal precipitation in the six-to-10 day outlook starting October 6th.”

Beginning this Sunday, TUD is asking all water customers to conserve during the annual, week-long Tuolumne Main Canal outage. Pacific Gas and Electric Co. owns the Main Canal ditches and flumes that convey 95% of TUD’s drinking water supply. The Main Canal shutdown is Oct. 3 to Oct. 10.

Most of Calaveras and Tuolumne counties remained in exceptional drought on Friday, the most dire category used by U.S. Drought Monitor scientists. More than four-fifths of the Golden State, including the entire north, central, and southern Sierra Nevada range, was in severe drought.

“Sonora and much of the surrounding area is currently in D4 or exceptional drought,” Shoemaker said Friday. “These conditions are likely to persist until significant precipitation occurs.”

The Central Sierra and the rest of California are currently forecast to have a second consecutive La Niña this winter, on the heels of last winter’s La Niña for 2020-2021. Shoemaker said the La Niña pattern “brings a slight tendency for drier conditions over the winter for the Sonora area and the forecast from the Climate Prediction Center leans towards a slight trend for another dry winter.”

Contact Guy McCarthy at gmccarthy@uniondemocrat.net or 770-0405. Follow him on Twitter at @GuyMcCarthy.

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