This winter’s major storms laid down one of the largest snowpacks recorded in California’s Sierra Nevada, along with an unusual amount of snow at low mountain elevations.
But such prolific snowfall at lower elevations is set to become increasingly rare in coming years as climate change drives temperatures higher, according to new research.
Floods, swollen rivers, road closures — Colorado’s spring runoff season is in full swing and much of the snow in the state’s mountains hasn’t melted yet. Colorado saw higher-than-average snowfall build up on the Western Slope this year, a boon for irrigators and other water users who rely on the Colorado River Basin which spans Colorado, tribal lands, six Western states and parts of Mexico. But the snowmelt, with the help of recent weather, is leading to high runoff and its adverse impacts are popping up around the state like a game of whack-a-mole.
The California Department of Water Resources May 1 conducted the fifth snow survey of the season at Phillips Station. The manual survey recorded 59 inches of snow depth and a snow water equivalent of 30 inches, which is 241% of average for this location on May 1. The last time there was measurable snow at the Phillips snow course on May 1 was 2020, when only 1.5 inches of snow and .5 inches of snow water equivalent was measured
DWR’s electronic readings from 130 snow sensors placed throughout the state indicate the statewide snowpack’s snow water equivalent is 49.2 inches, or 254% of average for May 1.
The snow water equivalent measures the amount of water still contained in the snowpack and is a key component of DWR’s water supply run-off forecast.
“While providing a significant boost to California’s water supplies, this year’s massive snowpack is posing continued flood risks in the San Joaquin Valley,” said DWR Director Karla Nemeth. “The snowpack will not disappear in one week or one month but will lead to sustained high flows across the San Joaquin and Tulare Basins over the next several months and this data will help us inform water managers and ultimately help protect communities in these regions.”
Snow surveys like the one at Phillips Station are critical to planning for impacts of the coming snowmelt runoff on communities. DWR uses the most updated technology to gather data from snow surveys, a network of 130 remote snow sensors, and airborne snow observatory data to gather information on current real-world conditions to create the most accurate snowmelt runoff forecasts possible. These runoff forecasts, published through DWR’s Bulletin 120, allow reservoir operators to plan for anticipated inflows and water managers downstream of reservoirs to plan and prepare for flood risks.
Despite a brief increase in temperatures in late April, the statewide snowpack overall melted at a slower pace than average over the month of April due to below average temperatures early in the month and increased cloud cover. An average of 12 inches of the snowpack’s snow water equivalent has melted in the past month and it now contains an average of 49.2 inches.
“The snowpack will not disappear in one week or one month but will lead to sustained high flows across the San Joaquin and Tulare Basins over the next several months… pic.twitter.com/zIOiGMm0I7
— CA – DWR (@CA_DWR) May 1, 2023
“No matter how you look at the data, only a handful of years in the historical record compared to this year’s results,” said Sean de Guzman, manager of DWR’s Snow Surveys and Water Supply Forecasting Unit. “Survey results from our partners in the California Cooperative Snow Surveys Program and other data, including data from Airborne Snow Observatory flights, allow us to incorporate these data into our models to provide the most accurate snowmelt runoff forecasts possible right now to inform water supply, flood control, and planning.”
@CA_DWR uses data from the 5/1 snow survey as well as ASO aircraft-based LiDAR & remote snow sensors to forecast & supply current conditions of the snowpack in real-time & provide water managers, #flood agencies & emergency responders the most accurate snowmelt forecasts possible pic.twitter.com/dsuRxt1ORJ
— CA – DWR (@CA_DWR) May 1, 2023
According to historical records, only the April 1 measurements from the years 1952, 1969, 1983 and this year were above 200 percent, although it is difficult to directly compare individual years across the decades due to changes in the number of snow courses measured over time.
Due to the impact of climate change on California’s snowpack, since 2021, snowpack averages have been calculated using a timeframe of 1991 through 2020 so that results better reflect the current climate conditions.
DWR is maximizing the amount of water that can be stored and diverted from this record snowpack.
In April, DWR announced a 100% allocation of requested supplies from the State Water Project, which delivers water to 29 public water agencies that serve 27 million Californians and 750,000 acres of farmland. The last time the SWP allocated 100% was in 2006. DWR is also maximizing the amount of water that can be diverted towards recharging groundwater basins so more water is stored for future use in underground reservoirs.
Last week, Governor Newsom visited the Tulare Basin to tour flood impacts first hand, met with community leaders and emphasized the state’s commitment to supporting and providing appropriate assistance to counties impacted by recent and anticipated flooding this spring and summer.
Snowmelt runoff forecasts are an instrumental part of the assistance provided by DWR’s State-Federal Flood Operations Center (FOC), which is supporting emergency response in the Tulare Lake Basin and Lower San Joaquin River by providing technical and materials assistance to support ongoing flood response activities.
Storms this year have caused impacts across the state including flooding in the community of Pajaro and communities in Sacramento, Tulare, and Merced counties. The FOC has helped Californians by providing more than 1.4 million sandbags, 1 million square feet of plastic sheeting, and 9,000 feet of reinforcing muscle wall, across the state since January.
May Drought Outlook by @NOAA’s @NWSCPC
Some potential improvement in the drought-stricken Southern Plains. Also the East, Gulf Coast, and a bit of CA/NV.
Drought may develop on the Eastern Plains and Midwest including part of KS, NE, IA, MO, and IL.
Otherwise, drought persists pic.twitter.com/OfVbjzpMbh
— NIDIS Drought.gov (@DroughtGov) May 1, 2023
(Editor’s Note: Information in this story was provided by the California Department of Water Resources).
An extra pulse of water has been sent through the Grand Canyon this week. The Bureau of Reclamation is running a “high-flow experiment” at Glen Canyon Dam in northern Arizona, which means a big release of water designed to move and redeposit sand and sediment will make its way downstream from the dam. This experiment is the first since 2018, and comes in response to forecasts for an above average spring snowmelt in the Rocky Mountains.
After weeks of uncertainty, forecasters say an incoming California heat wave will trigger rapid snowmelt on the slopes of the Sierra Nevada and cause more flooding in portions of the San Joaquin and Owens valleys this week.
Temperatures in Central California are forecast to climb into the high 80s and mid-90s beginning Wednesday and into the weekend, with the potential for some areas to approach daily records.
After a three-year drought in California and throughout the Southwest, many states throughout the West are measuring record snowpack conditions at NRCS SNOTEL stations and snow courses. Utah especially has seen a benchmark year for snowfall levels throughout the state.
In California, the statewide snowpack (April 5) was 243% of normal, with the Northern Sierra at 198%, Central Sierra at 242%, and Southern Sierra at 302%. The California Department of Water Resources reported that the 2022-23 season will go down as one of the largest snowpacks on record in California.
California's snowpack is one of the biggest ever. DWR is reaching new heights to capture data to inform water supply forecasting and help local agencies plan for the spring snowmelt season.
–#california #water #cawater #snow pic.twitter.com/M2dbcy3Ej0— CA – DWR (@CA_DWR) April 5, 2023
In Nevada and Utah, current SWE percentages of median for select basins are as follows: Central Lahontan 273%, Central Nevada Desert Basins 267%, Great Salt Lake 224%, Lower Green 202%, Upper Colorado-Dolores 207%, and Upper Colorado-Dirty Devil 219%, according to the NRCS SNOTEL network.
“A significant Western warming trend during the weekend and early next week will increase streamflow due to melting snow. On April 10-11, temperatures should briefly top 95°F in lower elevations of the Desert Southwest. Periods of Northwestern precipitation will add to the runoff potential in that region. Meanwhile, little or no precipitation will fall during the next 5 days across a vast swath of the country, including southern California and the Plains, Southwest, Midwest, and Northeast.
The #Sierra snowpack is near its climatological peak, and looking at today's numbers from @CA_DWR, the statewide percent of avg sits at 243% for April 5. The southern Sierra is an "eye-popping" 302% of avg. Track the melt into area rivers at https://t.co/Vab3udGkyz #CAwater #CAwx pic.twitter.com/k7FKQP92kl
— NWS California-Nevada RFC (@NWSCNRFC) April 5, 2023
Farther south, however, 5-day rainfall could total 1 to 3 inches or more from eastern Texas to the Carolinas, with the bulk of the rain falling by Saturday. The NWS 6- to 10-day outlook for April 11 – 15 calls for the likelihood of below-normal temperatures in California, the Great Basin, and the Northwest, while warmerthan-normal weather will dominate the central and eastern U.S. Meanwhile, above-normal precipitation from the Rockies into the Plains and upper Midwest should contrast with drier-than-normal conditions in the East (excluding Florida’s peninsula) and much of California.”
It’s snowing today in the central Colorado Rockies, likely the last hurrah for a year to remember for everyone who depends on water from the Colorado River — including Las Vegas.
It’s just past the early April peak when scientists calculate the final snowpack levels for the year. Today, that measurement hit 160% of normal, just above where it was a week ago.
Following three consecutive years of drought in California, the Sierra Nevada snowpack is one of the most bountiful in more than 40 years. While the record snowpack and snow water equivalent is great news for water supply, there are concerns the record snowpack could create flooding issues.
The Bureau of Reclamation March 28, announced an increase in Central Valley Project 2023 water supply allocations. After below average precipitation in February, Reclamation announced a conservative initial water supply allocation for the CVP on Feb. 22. Additional atmospheric river systems have since boosted hydrological conditions and storage volumes, allowing for a more robust water supply allocation.
Since making initial allocations last month, Shasta Reservoir, the cornerstone of the Central Valley Project, has increased from 59% to 81%, and San Luis Reservoir, the largest reservoir south-of-Delta, from 64% to 97%. Record-breaking snowpack conditions currently exist in the Southern Sierra coupled with significant snowpack in the Central Sierra and Northern Sierra/Trinity.
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