How Can We Capture Pasadena’s Ground Water?

Pasadena Public Works construction(Photo – cityofpasadena.net)

After weeks of abundant rainfall this winter, small rivers have formed in both the Arroyo Seco and Eaton Canyon. Each has been so voluminous that significant lakes have formed behind Devil’s Gate Dam and the Eaton Canyon Flood Control Dam, and have risen to levels not seen in many years.

By Brian Biery

According to statistics from California Water Watch, our region has been inundated with 206% of our average rainfall so far this year; up from about 17 inches per year, to over 35 inches to date.

Why is this unique year, filled with atmospheric rivers and torrential downpours, so significant? About 40% of Pasadena’s water needs are met through local water production. Beneath Pasadena and Altadena lies an enormous natural water storage formation called the Raymond Basin aquifer, which includes the Monk Hill Sub-Basin below Hahamongna Watershed Park.

As the result of continuous pumping of approximately 13 million gallons per day, even in low-rainfall years, the Raymond Basin water level lies more than 350 feet below its level in 1910, the year that Pasadena Water and Power started tracking water usage of the basin.  One reason for this dramatic drawdown is that local water costs about a quarter of the price of imported water from the Metropolitan Water District (Colorado River or State Water Projects).  Thus, in an effort to maintain prices at affordable levels, PWP has prioritized using water from the Raymond Basin.

Prior to the era of flood control channel construction that lined Southern California’s river system with concrete, water was absorbed by the earth and naturally filled the aquifers of the region.  According to a recent analysis conducted by Friends of the LA River (FOLAR), today nearly 80% of the water ends up in the ocean.

In order to slow water transport and allow for filtration, a movement to deconstruct the concrete flood control channels has developed throughout the watershed.  In the Arroyo Seco several hundred feet of concrete was removed under the Colorado St. and 134 Freeway bridges.  Other similar conversion projects have occurred on sections of the Los Angeles River, which has resulted in greater water absorption, habitat restoration and expanded wildlife refuge.

There are many other innovative methods for capturing stormwater in order to recharge our local groundwater system. The City of Pasadena hired Dawn Petschauer to run its stormwater recapture program through the Public Works Department. As the Stormwater Program Administrator, she will be coordinating several dynamic aquifer recharge projects.

The Brookside Park Stormwater Capture Project

The Brookside Park Stormwater Capture Project has the potential to infiltrate 1,166 acres of runoff per year.  The essential components of this project include the construction of a storage tank under the parking lot, which will capture storm water and use a water treatment system to clean it before it infiltrates the aquifer.  Water treatment is needed, particularly in this case, because runoff water will be coming from streets and parking lots covered with oil, gasoline and other toxic materials.

The Sierra Madre Boulevard Green Street Stormwater Capture Project

The Sierra Madre Boulevard Green Street Stormwater Capture Project is another valuable project under Petschauer’s purview. It is designed to divert surface water to a series of bioswales that will be built in the median. The function of bioswales is to create vegetated channels to pool water in areas where it is able to percolate into the ground. Bioswales also are able to serve as natural filters for surface water as they effectively remove contaminants and debris. In addition to work on the median in the form of bioswales, the project will also utilize several runoff storage tanks, similar to those that will be at Brookside Park, to treat and then infiltrate stormwater into the aquifer.

Individual homeowners, businesses and multi-family buildings

Individual homeowners, businesses and multi-family buildings can take steps to bolster our capacity to augment the local water supply. “Residents and businesses should consider converting their landscapes to native plants, adding hugels or bioswales, and removing unneeded hardscape,” she suggested in a recent interview. “Reducing our water usage through conservation and efficiency measures are extremely valuable actions.”

All of these strategies will be needed to replenish our local water supply. Future Measure W projects will require public input, so it will be important for community members to stay abreast of those proposals. For updates on the City’s Stormwater Management Program visit the Public Works Department’s construction web page to view the progress of the City of Pasadena’s current stormwater capture projects.