Devil’s Gate to Eaton Canyon Water Conservation Project


The Foothill Municipal Water District held a special meeting on Aug. 22 to discuss and gather information on, among other things, a new project proposed by the L.A. County Flood Control District to help replenish the groundwater basin beneath Pasadena.

A portion of the water used in homes and businesses comes from underground groundwater basins known as aquifers. During a drought, those aquifers become even more important and are relied upon more heavily without rainfall to replenish it. The rain that does come down hits concrete and runs off, flowing into storm drains and flood channels to go out to the sea, because there are few systems in place for capturing that rainwater.

A new system proposed by LACFCD at the FMWD meeting involves getting the overflow water from the channels into a spreading ground where it can seep back into the groundwater.

“Part of [LACFCD’s] mission is to conserve water for local water supply, and that includes being able to recharge into the groundwater basin,” said Nina Jazmadarian, general manager of FMWD. “Groundwater levels are dropping so they are trying to put together projects that will store water into the Raymond basin. Part of the project is moving the water from behind Devil’s Gate dam to the Eaton Canyon spreading ground.”

The Raymond basin aquifer, which supplies 41% of Pasadena’s water use, runs underground approximately from Devil’s Gate dam to the Santa Anita area. There are recharge areas like Hahamongna watershed park, the Arroyo Seco Spreading Grounds, which allow water from rainfall to collect and slowly go back into the basin. This takes exposed areas of land which are open to let water collect like a dam but wider and only full while water is waiting to seep in.

The plan proposed is to build a pipeline running six miles from Devil’s Gate dam to Eaton Canyon spreading ground where the excess rainwater can be absorbed. So instead of running off to the sea, it can be captured for use.

“[Eaton] can actually hold and recharge quite a lot. They would be able to conserve, in a wet year, 1,130 acre feet, and that’s about 326,000 gallons – enough for two households per year,” Jazmadarian said. The project overall would conserve 2,400 acre feet per year between the Arroyo Seco and Eaton spreading grounds. And to visualize the true volume of water saved, Jazmadarian added, just one acre foot is enough water to cover a football field, one foot deep.
The proposed project would improve the capture rate and recharge of the Raymond basin, but the Verdugo basin, which supplies water for the Crescenta Valley Water Dept. as a retail agency of FMWD and faces a similar drop in groundwater levels, will be unaffected.