Wine and Water

Geology helps quench Atascadero’s thirst

One of the city’s primary water sources is a sub-basin that replenishes itself via rainwater much more effectively than the main basin

tstrickland@thetribunenews.comJune 19, 2013 

Atascadero uses water from the same general basin as Paso Robles, but studies from 2006 show that it’s not facing the same level of water shortage — yet.

The key reason: Atascadero draws water from a sub-basin, a pocket located on the western edge of the main basin (just 3 percent of the basin) that is smaller, narrower and replenishes water far more easily with rainfall. The Rinconada Fault separates the two. Atascadero also draws water from the Salinas River underflow over the sub-basin and, since 2010, gets 2,000 acre-feet per year from Nacimiento Lake.

Although county officials are re-evaluating how the water table in the main basin and sub-basin affect each other and what might happen in the long term, the distinction is good news for Atascadero.

The city’s long-term planning document outlines an expectation to grow by an estimated 36,308 people by 2025 — about 7,600 more than the current population of 28,687. That count could further expand by about 1,500 people with the largest potential annexation in the city’s history, Eagle Ranch. The project, not yet approved, could add nearly 600 homes, shopping and lodging on 3,460 acres just outside the city’s southwest edge.

Mutual Water Co.

The Atascadero Mutual Water Co., a nonprofit water utility, delivers water to about 30,000, including Atascadero property owners, the city of Atascadero’s operations, and about 1,600 people in San Luis Obispo County’s unincorporated areas.

Last year, 32 percent of Atascadero’s water came from the sub-basin, while 68 percent came from underflow in the Salinas River. Atascadero also used Nacimiento water for a short time last year and will use it again this summer, said John Neil, general manager of Atascadero Mutual Water Co. The lake water goes into a recharge basin and is captured later through the water company’s existing wells, so it isn’t separately tracked.

The water company doesn’t need a treatment plant because the natural geology along the Salinas River in Atascadero allows it to treat the water by filtering it through a sandy layer adjacent to the Salinas River, Neil said. The water is also disinfected with chlorine before being delivered to customers.

The majority of the utility’s water goes to residential users, nearly 85 percent last year. Landscape users such as city parks and schools followed, with nearly 7.5 percent. Commercial users are at about 7 percent. Motel and industrial users together make up less than 1 percent.

Its 10,338 customer accounts are tapped into 100-year-old riparian water rights that city founder E. G. Lewis established in 1913 when he bought a 23,000-acre ranch along the Salinas River to build his colony. The ranch had overlaying rights to the sub-basin, since it touched its southern edge.

Before slicing the ranch into smaller properties, Lewis deeded those overlaying water rights to the water company so their benefit stayed with the colony’s parcels, regardless of proximity to the river or sub-basin.

That means that Atascadero property owners are all shareholders in the water company, and because of their water rights, they would get a better deal should the basin issues be fought over in court, Neil said.

Eagle Ranch was originally part of Lewis’ colony, although its lots were never developed. So anyone who buys land there would become a water shareholder. For that reason, water for that development is seen as a nonissue for the water company.

“We know we have an obligation to serve them,” Neil said. “So when we look for water resources, we account for that demand.”


Like Paso Robles, the Atascadero Mutual Water Co. encourages conservation — a step it began in the 1990s after a water shortage hit when the utility lacked enough wells. Among its water-saving efforts: rebates for installing low-flow appliances and replacing turf, as well as educating the public on ways to reduce usage.

Some large facilities get their water elsewhere. For example, Atascadero State Hospital, a psychiatric facility licensed for 1,275 beds, runs on its own system of wells by the Salinas River. The one golf course in Atascadero — Chalk Mountain Golf Course, which is run by the county — is irrigated with reclaimed water from the city of Atascadero’s sewer plant.

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