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As a result of the atmospheric river weather phenomenon, California has experienced higher than average rainfall in water year 2019. Graphic: National Weather Service

Atmospheric Rivers Benefit State, Regional Water Supply

Atmospheric river events in late January and in February have significantly increased snowpack in the Sierra Nevada and the Rocky Mountains, key sources of water supply for the state and San Diego County.

“We’re thrilled by the amount of precipitation – rain and snow – in San Diego County, the Sierra and the Rockies,” said Dana Friehauf, a resource manager with the San Diego County Water Authority.

The statewide Sierra Nevada snowpack was 151 percent of normal at 104 reporting stations for February 27, according to the California Department of Water Resources. The Rockies have received significant snowfall, which will feed the Colorado River, a source of water supply for the Water Authority. The amount of precipitation in most of the Rocky Mountain region, has ranged from 100 to 150 percent for Water Year 2019 through February 25, according to data from the Natural Resources Conservation Service. The percentage is based on the median between 1981 and 2010.

As a result of the atmospheric river weather phenomenon, California has experienced higher than average rainfall in water year 2019. Graphic: National Weather Service

As a result of the atmospheric river weather phenomenon, California has experienced higher than average rainfall in water year 2019. Graphic: National Weather Service

Record rainfall recorded in San Diego

Locally, a bountiful February has helped make Water Year 2019 one of the wettest on record at Lindbergh Field. Preliminary data from the National Weather Service indicates 10.62 inches of precipitation at the San Diego International Airport, with 3.42 inches coming so far in February 2019.

The Weather Service report issued Feb. 24 also shows that last year at this time, just 1.91 inches of precipitation had been recorded at the airport (for Water Year 2018).

In fact, Water Year 2018 (October 1 – September 30) was the second-driest on record since 1850 at Lindbergh Field, with just 3.3 inches of rain, or 32 percent of the long-term average.

Friehauf reminds San Diegans that even in years such as this, when rainfall is plentiful, that water-use efficiency remains a way of life. For instance, each rainstorm is an opportunity to turn off irrigation systems for days or even weeks at a time. She also suggests residents use rain barrels to collect or “harvest” water that can be used later, when the weather is drier.

Capturing the water from gutters and downspouts also reduces the amount of water flowing into storm drains. Homeowners can get rebates on residential rain barrels. Find details on rain barrel rebates here.

 

 

 

 

 

San Diego’s airport reported 3.98 inches of rain between the start of the 2019 water year on Oct. 1 and Dec. 7, according to the National Weather Service. Photo: James Arnott, Flickr/Creative Commons License Wat

Late-Fall Storms Improve Water Outlook Statewide

San Diego welcomed an unexpectedly large amount of rain since mid-November, surpassing last year’s rainfall total in just the first 10 weeks of the season.

Following the latest storm, two-day precipitation totals on Dec. 7 showed rainfall of 2.6 inches at San Diego’s Lindbergh Field, San Diego’s official weather station. Regional readings ranged from a high of 3.23 inches in the University Heights area of San Diego, to 1.1 inches in Lakeside and less than an inch in the county’s desert areas.

San Diego’s airport reported 3.98 inches of rain between the start of the 2019 water year on Oct. 1 and Dec. 7, according to the National Weather Service.  Just over three inches of rain was recorded at Lindbergh Field between Oct. 1, 2017, and Sept. 30, 2018 – the second lowest total since 1850.

To put the water season in perspective, average rainfall at this time of year is about 1.8 inches.

Sierra Nevada Snowpack off to a Fast Start

In Northern California, late-fall storm systems have dropped a generous amount of snow in the Sierra Nevada, which had been very dry through mid-November. Many mountain areas are reporting twice the average snowpack for mid-December.

More than 60 percent of the state’s water supply comes from Sierra Nevada snowpack as it melts and releases water to lower elevations.  The more snow that falls each winter, the more protection the state builds against drought the following year. 

The news is also positive in the Rocky Mountains, though the Upper Colorado River Basin has been struggling with drought for nearly two decades. Rainfall was at 119 percent of average in mid-November.

San Diego Region has Sufficient Supplies for 2019

For San Diego County, the National Oceanic and Atmospheric Administration’s Climate Prediction Center’s three-month weather outlook for December through February predicts above-normal precipitation across all of California except the very northern tier. The agency also predicts above-normal temperatures for the western states, with a greater than 40 percent probability of above-normal temperatures this winter statewide.

Even if weather conditions were to dry out through September 2019, the Water Authority and its member agencies have enough water supplies to meet regional demands for the foreseeable future. This is possible due to a combination of drought-resilient local and regional water resources, including the Claude “Bud” Lewis Carlsbad Desalination Plant, conserved agricultural water transfers, savings from canal lining projects, and continued water-use efficiency measures.

A weak El Nino is expected to form and continue in the Northern Hemisphere this winter and into the spring. As a result, the U.S. Seasonal Drought Outlook released on Nov. 15 favors drought improvement or removal for California and the southern portion of the Southwest.

Meteorologist Alex Tardy of the National Weather Service San Diego office predicted near-average precipitation in the region in his 2018-2019 outlook, noting that “past precipitation events have been extreme” with extended dry periods between storm patterns that bring heavy rain.

NOAA's three month weather outlook predicting the amount of rainfall across the U.S. Map: NOAA.gov

Water Supplies Sufficient for 2019 Demands Despite Hot, Dry Weather

At the start of the 2019 water year, the combination of diversified water supplies and water-use efficiency means the San Diego region has enough water for 2019 and the foreseeable future despite historically low rainfall over the past 12 months.

“It has been very hot and dry, but we have invested wisely in infrastructure and regional water-use remains well below where it was at the start of the last drought,” said Jeff Stephenson, a principal water resources specialist with the Water Authority. “In fact, potable water use over the past three-plus years was 17 percent below 2013, which shows that San Diego continues to live WaterSmart.”

Still, said Stephenson, “we are looking for a wet winter locally, and in the Sierra and Rocky Mountains, to help replenish reserves for future years.”

Water managers use “water years” that run from October 1 through September 30 to track rain and snow. Local rainfall during water year 2018 totaled just over 3 inches at Lindbergh Field – 67 percent below normal and the second-lowest in San Diego history dating back to 1850.

In addition, local temperatures have been significantly above normal for most of the past five years. In many of those months, the average daily maximum temperatures were more than 4 degrees above long-term averages.

Forecasts predict continued warm weather conditions through December

The National Weather Service’s Climate Prediction Center forecasts continued warm conditions for California through December, with a 33 percent probability of above-normal precipitation locally. The U.S. Drought Monitor’s classification of San Diego County as an area of “Severe Drought” is based on weather factors – but it does not reflect water supply conditions.

More than $3.5 billion in regional water investments by San Diego County ratepayers over the past three decades mean water supplies will meet demands regardless of the weather.

New supplies and infrastructure upgrades include the Claude “Bud” Lewis Carlsbad Desalination Plant, which delivers approximately 50 million gallons of potable water per day for regional use, along with a ramp-up of water delivered to San Diego County as part of a long-term water conservation and transfer deal signed in 2003.

Other regional assets include the storage of 100,000 acre-feet of water behind the raised San Vicente Dam due to conservation efforts during the last drought. In addition, many key reservoirs statewide, including Diamond Valley Lake in Riverside County, remain near average levels for this time of year. Significantly, no shortages are expected on the Colorado River system in 2019, though long-term drought conditions continue to be a concern across the Southwestern U.S.

The Water Authority offers several programs, including a Landscape Transformation program rebate, to promote water-use efficiency. Residents and business can also attend free sustainable landscaping classes, and access online videos and tips. To learn more about those resources and others, go to WaterSmartSD.org.