California snowpack is 110% after wet season. What to know about state's water supplies

Gov. Gavin Newsom trekked into the mountains with state officials early this week as they conduct their last snowpack measurement of the season. The expected result: an above-average year, the second in a row.

After a slow start last fall, California’s wet season ended April 1 with the Sierra Nevada snowpack measuring 110% of its historical average. Last year’s snowpack tied with 1952 for the highest on record — a whopping 221% of average, measuring 126.5 inches.

The snow is essential for funneling large volumes of water south to 27 million people, mostly in Southern California, and 750,000 acres of farmland via the State Water Project. So far, agencies served by the massive system of dams and aqueducts have been allocated just 30% of the water requested, although that amount is often adjusted later.

Reservoirs statewide are in good shape for the dry months to come: Eleven of the state’s 12 major reservoirs are storing more than 100% of average.

It’s been a soggy season in the rest of California, too. Statewide rainfall is 104% above average. Downtown Los Angeles had had the “second-wettest back-to-back years since records began in 1877,” according to the National Weather Service. More than 52 inches of rain fell there during the past two wet seasons.

But that doesn’t mean California no longer faces chronic water shortages. Groundwater in the San Joaquin Valley has been drained more quickly than it can be recharged, so thousands of wells are still dry. The Colorado River still doesn’t have enough water to meet the demands of farms and cities in seven states. And droughts are becoming more common and more extreme as the climate crisis intensifies.

Key California snowpack by the numbers

• 0% of the state's total area is experiencing drought conditions. The previous drought lasted 1,337 days (Feb. 11, 2020 to Oct. 10, 2023)
• 30% of State Water Project contracts will be met in 2024. The updated allocations for March 2024 are lower than the 75% allocation last March, and it takes into account snow pack levels up to March 1.
• Average statewide snow water content is 29 inches as of April 1, 2024.
• Urban water use between January 2023 and 2020 is down 9.7%.
• 393 households are reporting water shortage over the past 365 days. That's down 74% compared to the previous 365 days.
• 33% of ranked wells are at historic lows.
• Current systemwide reservoir capacity is at 75%. Eight of 12 major state-owned reservoirs at 75% or higher capacity.
• Average statewide precipitation is 104% compared to historical average for the water year, as of April 1, 2024.

Is California still in a drought?

No. As of the week of October 10, 2023, California finally ended its latest drought cycle, which lasted 1,337 days (about 3.5 years). The previous drought lasted 2,672 days between 2011 and 2019. As of March 26, 2024, about 0% of the state's total area is seeing drought conditions.

How full are California's reservoirs?

The State Water Project manages 24 California reservoirs. Reservoir levels are currently 18 million acre-feet of water. The system can store 24 million acre-feet of water, putting us at 75% of capacity.

The fundamental challenge with water in California, at least the above-ground supply, is that most of it isn't where most of the people are.

Much of California’s water falls as snow in the Sierra Nevada and other northern mountain ranges. To satisfy human demands, we have transformed the state’s natural water systems to transport water hundreds of miles from its source.

The federal government built the Central Valley Project, which primarily conveys water from Northern California to irrigate crops in the San Joaquin Valley.

The state built the California Aqueduct, which snakes down the Central Valley for more than 400 miles. Much of the water in the state aqueduct moves downhill by gravity.

But it's not all downhill from there. To get over the Tehachapi Mountains near Los Angeles, the water is pumped nearly 2,000 feet high by the most powerful water lifting system in the world.

In addition, Los Angeles has built its own system, the Los Angeles Aqueduct, to carry water from the Owens Valley into the city.

But none of that is enough. The Colorado River, which winds through four other states before reaching the southeastern tip of California, is another major source. The state is entitled to 4.4 million acre-feet of water a year under a multi-state contract. But it's difficult to know how much will be available in the coming decades. The US Geological Survey estimates that the river's flow, once mighty enough to carve the Grand Canyon, will decline by nearly a third over the next 30 years because of climate change.

The Metropolitan Water District, which provides drinking water to more than 19 million people in Southern California, operates the Colorado River Aqueduct to carry water from the eastern edge of the state across the desert and into the Los Angeles basin. This aqueduct supplies about a quarter of the district’s water.

How much water came from rain?

For the current water year, the statewide precipitation amount is 104% of its historical average.

• Rain helps increase reservoir levels, and it seeps deep into the ground to help replenish underground aquifers.
• Too much water over a short period of time can be bad, leading to flooding and mudslides which damage property and put people at risk.
• Prolonged drought conditions make it more difficult for rain to seep into the ground, as the ground tends to be harder and not as porous as it would be with more moisture.

How much water came from snow?

The average measurement across the state as of April 1, 2023 was 61 inches, 233% of April 1 average.

• When rain falls as snow, it freezes and creates a water reserve for warmer times of the year. This water, when it melts, washes back into waterways and into the ground, supporting our water needs when rain isn't in the forecast.
• The California Department of Water Resources uses a metric called "snow water content" to measure how much water is frozen.
• Historically most snow has fallen by April 1, so scientists compare the snow water content from that day to the same day in previous years to access how likely the state will be to satisfy water requests.
• California's statewide snowpack on April 3 tied with 1952 for the highest on record for that date. Meanwhile, snow water content in the central and southern Sierras broke records, while in the northern Sierras snow water content levels are second to recorded historical levels from 1983.

How much water ends up in streams?

On April 02, 2024, 1% of streams were at or near their lowest level in history.

• The US Geological Survey has gauges in streams across the state and continuously measures their flow.
• Like all water data in California, these measurements are very spiky and hard to understand. But we can compare each stream to its past measurements.

Who will get that water?

The allocation is 30% as of March 22, 2024. The updated allocations for March 2024 are lower than the 75% allocation last March, and it takes into account snow pack levels up to March 1.. The last time the allocation was 100% was 2006.

• The State Water Project doles it out based on a system dating back to the Gold Rush.
• Those who take the water deliveries are called contractors — mainly agencies managing water for residential, industrial, recreational and agricultural use.
• Several times a year, the project announces what percentage of a contractor's request will be allocated for the water year. In times of extreme drought, allocations tend to drop moving into the summer if snowpack levels disappoint expectations.
• The February allocation forecast update on Feb. 21 takes into account snow survey measurements and data up until Feb. 1.

More:Long-term Colorado River rescue plan at an impasse? It's north vs. south in the West

What's going on with urban water usage?

As of January 2023, statewide urban water use, compared to 2020, shrank by 9.7%. Californians in cities and towns used 6% less water from July 2021 through January 2023 compared to 2020 — falling far short of Newsom’s 15% goal.

• In mid-July 2021, Governor Newsom urged Californians to cut their water use by 15%. The ask is voluntary, for the moment, and there are no statewide emergency water mandates in effect.
• As such, the state is leaving it up to individual water suppliers to bear responsibility for the reductions and deciding on how to make it happen.
• Water suppliers are required to track residential water use. Using that analysis, the state is tracking both water savings from July 2021, and monthly water use compared to 2020.

What's going on with residential water use?

Residential water use statewide in January 2023 decreased to 58 gallons per capita used daily compared to the five-year average of 66.

• Since October 15, 2014, water suppliers are required to estimate or report the amount of water used for residential purposes. They are required to calculate per capita use monthly.
• This is often reflected as Residential Gallons Per Capita Day, or R-GPCD, a calculation based on the total population served by a water supplier verses the total water produced and used for residential use only over however many days are in that month.

What's going on with agricultural water use?

Good question; we really don't know. Unlike residential water use, collecting data on commercial agricultural water use is not required by law, and water suppliers occasionally supply that information.

• According to the California Department of Water Resources, agriculture accounts for about 80% of water use.
• The state does track the amount of water flowing to fields as they pass through water gates, but the data is unreliable, as water could flow back through the system and be double counted. Groundwater wells marked for agricultural use could also be measured, but the frequency varies (usually twice a year).
• CalMatters is currently working on ways to reliably, and accurately, track agricultural water use.

More:The 20 farming families who use more water from the Colorado River than some states

Groundwater wells: Household water shortages

Since 2014, 2022 Q3 saw the highest volume of reported household water shortages with 723.

• The California Department of Water Resources started a program in 2014 to more systematically track household water shortages, initially to help facilitate drought assistance.
• Most reported shortages occur during the summer months (Q3), regardless of whether there is a drought.
• The state provides county-level data on these reported shortages.

Groundwater well rankings

Of the 3,799 wells that meet the state's criteria for historical ranking, 32% ranked in the 25th percentile of lowest measurements. The California Department of Water Resources compares current measurements for wells with historical measures for the same month. At minimum, wells are measured twice a year in April (peak high) and October (peak low).

New groundwater wells

The median depth of completed wells was the highest since 2019 in July 2022 at 320 feet. There were 498 wells reported complete. The California Department of Water Resources maintains a database of applications for new wells and tracks their completion.

Land subsidence

A major risk of over-pumping an aquifer: triggering “land subsidence,” when the ground sinks slowly or suddenly due to shifts underground.

• The worst instances of land subsidence in California are occurring in the southern end of the San Joaquin Valley, where over-pumping for agriculture is common, even in non-drought years.
• Some areas in the San Joaquin Valley have sunk 100 feet below historic norms.

Want to get involved?

Interested in joining the conversation about how to protect your local water supplies from mismanagement or climate-induced disasters such as drought? Here are options:

• Contact your local water agency: These organizations directly manage water resources in their respective area.
• Contact your state legislators: Lawmakers can wield state policy to address the water crisis. CalMatters has a handy tool to help you find your legislators, and details about their work.
• Groundwater Sustainability Plans: You might want to get involved in how your local water agency manages this resource now and in the future. Scroll down for more.

Groundwater sustainability plans

Local water agencies must develop plans to avoid seawater intrusion, degrading water quality and land subsidence.

The Sustainable Groundwater Management Act gave local water providers in critically over-drafted basins 26 years — until 2040 — to stop the impacts of the overdraft from worsening, and until 2042 for those managing less-depleted water supplies.