Sonoma Water E-News | September 2021
Lake Mendocino Storage Drop Signals Worsening of Historic Drought
In a sign of a worsening drought that has already seen water storage drop to historic lows, Lake Mendocino fell below 20,000 acre-feet (AF) of storage on August 26, 2021, falling short of a water conservation goal established to maintain adequate downstream flows for fisheries and human health and safety needs for municipal users.

A minimum storage goal of 20,000 AF by Oct. 1, 2021 was recommended by the Sonoma County Water Agency (Sonoma Water) in the hopes of providing an adequate carry-over water supply entering the 2021-22 fall-winter rainy season. The reservoir’s storage level dropped below 20,000 AF on Thursday, August 26, signaling a worsening of the historic drought in the Russian River watershed.

Sonoma County Supervisor and Sonoma Water Board of Directors Chair Lynda Hopkins said, “We were hopeful that continued conservation among water users in the Russian River watershed could keep us above that conservation goal in Lake Mendocino. Unfortunately, the water-saving efforts in the Upper Russian River have not been enough, even with state action being taken to curtail water rights. We really urge everyone to step up their water saving efforts. The only way we’re going to get through this drought is if we all do our part.”
The reservoir’s storage level dropped below 20,000 AF on Thursday, August 26, signaling a worsening of the historic drought in the Russian River watershed.
Fourth District Supervisor and Sonoma Water Director James Gore said, “We need to take a regional approach to the drought. Recognizing the limits of our water supply, we must work together to continue to reduce consumption along the entire Russian River. Maintaining as much storage as possible in Lake Mendocino will keep enough water in the river for fisheries and human health and safety. We can meet that goal if we all work together.”
Water managers fear that as water levels drop in Lake Mendocino reservoir releases will not be able to meet minimum stream flows for fisheries and meet the human health and safety needs of downstream municipal users. In addition, there is concern that as the reservoir levels drop there may be a decline in water quality for downstream users.
“The City of Healdsburg is currently achieving a 55% reduction in water use and has been doing so for nearly two months,” said Healdsburg Mayor Evelyn Mitchell. “The City adopted high levels of conservation early in the summer because we knew storage in Lake Mendocino was an issue. We are hopeful the entire watershed will band together to achieve significant conservation as the timing of this year’s rain is uncertain.”
“I encourage all Sonoma County residents to demonstrate resiliency by respecting our new reality,” said Cloverdale Mayor Marta Cruz. “We can all make significant progress by reducing water use, collecting and re-using water as a measure to keep us safe & healthy!”
To learn more about the drought and ongoing water conservation efforts, please visit or
Sonoma Water and its Customers Reducing Diversions by more than 20%
The State of California has curtailed water rights for hundreds of water rights holders in the upper and lower Russian River regions and Sonoma Water has reduced its diversions from the Russian River by more than 20% over 2020 levels in response to drought conditions. Sonoma Water provides drinking water to more than 600,000 customers in Sonoma and Marin counties.

The Sonoma Water Cumulative River Diversions Plot graph below shows cumulative water savings by Sonoma Water customers for 2021 compared to 2020. Since July 1, we’ve reduced diversions from the Russian River by nearly 22%. Please keep up the good work -- every drop we save means more water in our reservoirs for the dry fall!
Sonoma Water has refreshed the weekly water supply graphic (below), to provide a snapshot of water storage for our two main reservoirs, Lake Sonoma, and Lake Mendocino. Stay informed about Current Water Supply Conditions, 2021 Drought Updates, Actions, and Information. For more drought information, visit
Supervisor David Rabbitt and Sonoma Water to Host Drought Town Hall
Sonoma County Water Agency and Second District Supervisor David Rabbitt will host a virtual Drought Town Hall on Wednesday, September 15 at 5:30 p.m. The Town Hall will be held utilizing a Zoom webinar. 

The focus of the meeting will be on the drought and impacts to the Second Supervisorial District and Russian River watershed. Speakers will include representatives from the Sonoma County Water Agency (Sonoma Water), City of Petaluma and the National Weather Service.

“The drought we are experiencing is unprecedented and this Town Hall is an opportunity to hear from residents about the challenges they are facing and to provide resources to help them make the best possible decisions,” said Supervisor David Rabbitt. “In the Second District our agricultural community is facing extremely hard choices and it is critical to find ways to support them through this drought.”

Representatives will discuss the drought, its impact to the southern Sonoma County community, drought response actions under way by Sonoma Water and a seasonal precipitation prediction for Sonoma County.
Learn more about the drought online.

Please click the link below to join the webinar on Wednesday, September 15 at 5:30 pm:

Passcode: 090962
Sonoma Water Explores New Project to Address Severe Drought
The Aquifer Storage and Recovery (ASR) project would store treated, high quality surface water in underground reservoirs, known as aquifers, during wet periods when Russian River water is plentiful. ASR is used to capture water when it’s available and send it underground (using new or existing wells). The stored water helps recover depleted aquifers and can help build up reserves to be used during droughts and emergencies.

Hydrologists refer to the Russian River watershed as ‘flashy’, meaning large storms known as atmospheric rivers, can turn normally mild creek and river flows into raging torrents in the space of hours. Lake Mendocino and Lake Sonoma were constructed to take the peaks off those high flows, store water and reduce downstream flooding. ASR represents a less costly and more environmentally friendly solution to our flashy system and can be used as part of a groundwater banking program.

In 2013, Sonoma Water, and local partners conducted a feasibility study for a regional groundwater banking program that would store surplus Russian River water produced at existing drinking water facilities in aquifers beneath the Santa Rosa Plain or in Sonoma Valley. Sonoma Water and the City of Sonoma piloted a successful, small-scale ASR project in 2018-2019.

Phase 1 of the Santa Rosa Plain Drought Resiliency Project would provide water to Sonoma Water customers by re-establishing the functionality of a groundwater production well in the Santa Rosa Plain. Sonoma Water owns three production wells within the Santa Rosa Plain. The wells were originally drilled in 1977 in response to the historic 1976-77 drought and their rehabilitation is a critical component of the regional drought and seismic emergency water shortage resiliency strategy.

In addition, the Phase 1 project will help drought-impacted farmers by providing supplemental water to the City of Petaluma (a Sonoma Water customer) for its water-hauling program. Phase 2 of the project will rehabilitate the two remaining wells and also add recharge (or ASR) capacity for at least one of the production wells. This would allow the well to work in ‘reverse’. Instead of pumping water out of the ground, the well would receive treated, high-quality drinking water when it’s plentiful. The water would be stored in underground reservoirs known as aquifers. This water would recharge the aquifer and would be available for use during future droughts and emergencies.
Through a policy known as ‘conjunctive use’, Sonoma Water increases its use of groundwater during droughts to offset declines in Russian River surface water. Secondly, during wet or normal water years, Sonoma Water reduces groundwater use to allow aquifers to recover. The production wells were last relied upon during the 2012-2015 drought years when they helped reduce Russian River water usage during those dry years. Increasing water conservation efforts during droughts is a third component of conjunctive use.

Sonoma Water’s production wells are deep (773 feet to 1,040 feet), and draw water from the deep aquifer, not the shallower aquifer. Monitoring from Sonoma Water’s network of 18 monitoring wells during the last drought period when the production wells were more consistently in use found that most home/private wells are connected to the shallower aquifer in the Santa Rosa Plain Basin and were not affected by the pumping. Similarly, creeks, streams, and the Laguna de Santa Rosa are connected to the shallower aquifer. Since groundwater-levels in the shallow aquifer system (which is connected to surface water sources like the Laguna de Santa Rosa) are not anticipated to be impacted by drought year pumping from these wells, streams and associated habitats are not expected to be affected. However, as part of planning and permitting ASR operations potential impacts to nearby well-users, creeks and water quality will be further assessed and monitored.
The Sonoma pilot project is the first ASR water supply approach to be tested in the North Bay region, and its success provides a blueprint for future permanent projects in the region. While the technology is new locally, ASR has been successfully applied to improve resiliency and sustainability of water resources in many other areas throughout the world by allowing stored water to be used in summer months or during droughts. ASR is a common water management strategy employed in California, the United States, and the world to increase water supply reliability.
For more information about the Santa Rosa Plain Drought Resiliency Project visit
Mark your calendars! Groundwater Community Meetings 
Groundwater Sustainability Plans in all three basins will be released in early October.

Community meetings are slated for the following dates:
  • Petaluma Valley – Thursday, October 7 
  • Sonoma Valley – Tuesday, October 12 
  • Santa Rosa Plain – Wednesday, October 13 

Meeting will be from 5:30-7:30pm 
For resources and basin information, please visit 

Rainfall and Water Storage Update
Current water supply conditions as of 9/8/2021:   
Lake Mendocino Target Water Supply Curve: 69,810 acre-feet   
Current Storage: 18,162 acre-feet (26.02% of Target Water Supply Curve)   
Lake Sonoma Target Storage
Curve: 245,000 acre-feet
Current Storage: 114,068 acre-feet (46.56% of Water Supply Pool)   
Current rainfall conditions (10/1/20 – 9/7/21)   
Average (1894-2020 water years): 36.64”   
Current Water Year: 12.53” which is 34.19% of average   
Santa Rosa:   
Average (1950-2020 water years): 30.38"   
Current Water Year: 12.86” which is 42.33% of average  
Upcoming Events

The Board normally holds its regular meetings on Tuesdays, beginning at 8:30 a.m. and will be facilitated virtually through Zoom and at Board of Supervisors Chambers (BSC) 575 Administration Drive 102A.

•Sept. 14, 2021 Virtual,BSC
•Sept. 17, 2021 Virtual Special Closed Session
•Sept. 21, 2021 Virtual, BSC
•Sept. 28, 2021 Virtual,BSC
•Oct. 4, 2021 BSC -Special Closed Session
•Oct. 5, 2021 BSC

Board Agendas: 

Please visit for additional information and resources

Groundwater Sustainability Agency Board Meetings

Sonoma Valley - September 27, 2021 4:00pm
Petaluma Valley - September 23, 2021 4pm
Santa Rosa Plain - September 30, 2021 1pm

Fact of the Month

Do not flush unused medications!

Traditional Wastewater Treatment plants are not designed to remove pharmaceuticals, which when flushed, can pass through the treatment plant and end up in the environment.

For more information and a list of locations where medications are accepted please visit
Employment Opportunities

Sonoma Water has job openings for people with a variety of skills and experience.

  • Water Agency Business Systems Analyst - Extra-Help (Continuous)
  • IT Department Internship
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