SLO County communities get more water from Nacimiento Lake

Nacimiento Lake, east of Paso Robles, is seen in April 2015.
Nacimiento Lake, east of Paso Robles, is seen in April 2015. jjohnston@thetribunenews.com

San Luis Obispo and some of its North County neighbors now have access to hundreds of thousands more gallons of water from Nacimiento Reservoir.

The San Luis Obispo City Council voted unanimously Tuesday to receive its full allocation from the Nacimiento Water Project, joining other water providers — Atascadero Mutual Water Co., the city of Paso Robles, and the Templeton Community Services District — that had signed a letter in September requesting additional water.

All of the water suppliers in the county with access to Nacimiento have now maxed out their shares with these latest allocations. The suppliers can use the water to reduce pressure on other sources such as groundwater, extend water supplies during future droughts or sell the water as surplus.

The county service area in Cayucos and two new participants — the Bella Vista mobile home park in Cayucos and Santa Margarita Ranch Mutual Water Co. — have also opted to purchase an additional allocation of Nacimiento water. On April 19, the San Luis Obispo County Board of Supervisors will decide whether Cayucos will take its extra share, county public works Deputy Director Mark Hutchinson said.

Then, acting as the board of the Flood Control and Water Conservation District, the supervisors will consider whether to sign contracts with the two new participants and confirm the five existing partners have met their contractual requirements to obtain the water.

Since 2011, the 45-mile-long Nacimiento pipeline has been delivering water from the lake, just west of Paso Robles, to as far south as San Luis Obispo.

The county secured the rights in 1959 to 17,500 acre-feet of water per year from Nacimiento Lake. The pipeline has the ability to deliver 15,750 acre-feet of water each year to communities within San Luis Obispo County. The rest of the water is used by residents around the lake, not pumped through the pipeline.

Until the recent request, the communities had been paying for 11,405 acre-feet of water a year, leaving a reserve of 6,095 acre-feet. (An acre-foot is equal to 325,851 gallons, or enough to generally serve about three households per year.)

Now, that supply will be maxed out. In Paso Robles, use of Nacimiento water would reduce groundwater pumping and provide one more high-quality water source for city residents, according to that city’s urban water management plan. Additional water “would allow the city to stabilize future basin well pumping,” the plan says.

In San Luis Obispo, the extra 2,102 acre-feet a year of water would be added to the city’s secondary water supply to make up short-term losses during a drought, infrastructure maintenance or repair, according to a staff report. The water is not considered a source to serve the city’s build-out population as envisioned in its General Plan.

“This water was not considered to actually be added to the primary water supply for the city,” Aaron Floyd, the city’s deputy water director, told the council. “If this water was being used to serve the needs of additional development, it would require additional (environmental) review.”

But that didn’t ease the concerns of several San Luis Obispo residents who have been seeking reassurance that the city will have enough water to serve its current population of about 46,730 residents — much less the 56,686 residents who could live in San Luis Obispo by 2035.

“I recommend we augment our Nacimiento water allocation. This ... will be absolutely necessary to sustain the existing population,” resident Allan Cooper said. “But this amount of water, without Whale Rock or Salinas (reservoirs), will not be sufficient to service any additional office, commercial, manufacturing, hospital or public sector development currently in the pipeline.”

“You cannot go on approving all this extra population,” San Luis Obispo resident David Brodie added. “We elect you to make sure we do have services and water to maintain us for the rest of our stay. A lot of us are intending to die here, so we’re going to be here for a while, even at my age.”

Utilities Director Carrie Mattingly told the council that the additional water would give the city more flexibility.

“If we needed to repair Whale Rock, we would have this in place,” she said by way of example. “At this stage, we’re not using it; we don’t need to use it. We have plenty of water for all our sources altogether.”

San Luis Obispo has four water sources: the three reservoirs and nonpotable recycled water.

In 2015, the city had 10,005 acre-feet of water available from those sources and used about 4,988 acre-feet. Adding the extra Nacimiento water raises the city’s total water supply to 12,107 acre-feet.

At the city’s build-out, with an estimated 57,200 people and other anticipated developments, San Luis Obispo would use 7,330 acre-feet a year, according to the city’s 2015 Water Resources Status Report. A community water forum is being planned for April 21 for residents to learn more about San Luis Obispo’s water sources, conservation and changes to the city’s water shortage response plan.

The additional Nacimiento water will cost the city about $75,000 to $107,000 a year, thanks to savings from refinancing of the water project bond last August and a one-time payment from the two new project participants, the Bella Vista mobile home park and Santa Margarita Ranch Mutual Water Co.

“Do you know of any other community in California or anywhere where a water supply could be secured at a cost of about $50 an acre-foot?” Councilman John Ashbaugh asked Tuesday.

“No,” Floyd replied.

Cynthia Lambert: 805-781-7929, @ClambertSLO

Where Nacimiento Lake’s water

goes in San Luis Obispo County

Totals listed are in acre-feet. An acre-foot of water is enough to serve about three households a year.







City of Paso Robles




City of San Luis Obispo




Atascadero Mutual Water Co.




Templeton Community Services District




Santa Margarita Ranch Mutual Water Co.




County Service Area 10A (Cayucos)




Bella Vista Mobile Home Park




Source: City of San Luis Obispo