Like other communities across the State of California, the City of San Luis Obispo is not immune to growing drought concerns.
What sets the City apart is the community’s long history of water-supply investments and water conservation. As a result, the City’s water supply is in a better position now than ever before to withstand extended periods of drought.
“The City is constantly looking for ways to conserve water, reduce water loss within the community, secure new water supplies, and build greater resiliency into our treatment plant and distribution system. Although we currently remain water secure, we always encourage the community to keep water conservation in the front of their minds to help preserve our most precious resource” said Mychal Boerman, City Utilities Department Deputy Director.
In fact, the City of San Luis Obispo’s drinking water system is the least vulnerable to supply impacts in San Luis Obispo County, according to a recent report released by the County of San Luis Obispo’s Water Resources Division. In response to previous drought conditions and in anticipation of future drought conditions, the County developed a Regional Water Infrastructure Resiliency Plan for mitigating vulnerabilities and enhancing reliability, resilience, and optimum utilization of existing and future regional water infrastructure. The report ranked the City of San Luis Obispo with the highest resiliency risk ranking of all water purveyors in the county.
Drought can result in significant operational impacts to water utilities, including a loss of water supply and poor source water quality. With the majority of San Luis Obispo County designated as a “Moderate Drought” area by the U.S. Drought Monitor and a below-average year of rainfall thus far, local water agencies are hoping for a repeat of March 1991, which became the year remembered for “miracle” rains that made it the third wettest March on record at the time. These rains came after several years of disastrous drought conditions that left many local communities impacted by water shortages.
The majority of the rainfall received this winter happened during storms in October and December. During November, January, and February however, County rainfall gauges at Salinas Dam (locally referred to as “Santa Margarita Lake”) recorded only 0.28 inches of rain combined over the three month period.
So, why has the City of San Luis Obispo remained in the Monitor Stage (5+ years of available water) as outlined by the City’s Water Shortage Contingency Plan (WSCP), and been ranked the least vulnerable water system in the County?
First, the City receives potable water from three local surface water reservoirs in different watersheds: Whale Rock, Salinas (Santa Margarita Lake), and Nacimiento.
As of March 1, 2022:
- Salinas Reservoir (Santa Margarita Lake) is at 63% of capacity, with 15,030 acre-feet of water stored
- Whale Rock Reservoir is at 77% of capacity, with 29,852 acre-feet of water stored
- Nacimiento Reservoir is at 29% of capacity, with 108,275 acre-feet of water stored
Today the City uses approximately 4,700 to 5,100 acre-feet of water each year. In 2010, the City’s available water supplies grew significantly when the City began receiving water from Nacimiento Reservoir. In 2016 the City increased its contractual water supply from Nacimiento Reservoir from 3,380 acre-feet to 5,482 acre-feet annually. Studies and recent data show inflows to Nacimiento Reservoir are sufficient to provide the City’s full Nacimiento 5,482 acre-foot per year entitlement, even in dry years. The addition of water from Nacimiento grew the City’s water supply portfolio to over 10,000 acre-feet of available water each year. The use of water from Nacimiento allows the City to preserve water stored in Whale Rock and Salinas reservoirs for use during critical water shortage periods.
Second, in 2006 the City began its production of recycled water for irrigation use in the City which helps preserve valuable drinking water supplies within local reservoirs. Today about 5% of the City’s total annual water use comes from drought-resilient recycled water produced at the City’s Water Resource Recovery Facility (WRRF).
To ensure that the City’s water resources remain adequate to meet demands as the City grows, the City estimates population growth and corresponding water demand through 2035. In addition to the water reserved to meet this future population, the City is also required, by policy, to have additional water set aside to act as a buffer in case of unforeseen or unpredictable long-term impacts to the City’s water supply, this supply is referred to as the City’s “Reliability Reserve”.
Finally, our community cares about water and community members do their part to be good stewards of our water supply. In fact, in San Luis Obispo, residential indoor water use for 2021 was well below the 2020 State-mandated amount and nearly met projected future mandated levels. In SLO, indoor water use was approximately 45 gallons per person per day on average. The State-mandated amount is 55 gallons per person per day and it is projected that the mandated level for year 2030 will be 42 gallons per person per day. The community’s total potable water use today is actually substantially lower than it was back in the 1970s, 1980s, 1990s, and 2000s, despite population growth over this time period.
Generations of focus on water supply planning, investments in diverse local water sources, and the support that comes from a community that embraces water conservation, are why the City of San Luis Obispo remains water-secure and resilient.
For more information on ways to reduce water consumption at your home or business, customers are encouraged to visit slocity.org/water or call (805) 781-7215 to speak with a Water Resource Technician.