correction in bold

By Mary O’KEEFE

The Rosemont Preserve, part of the Arroyos & Foothills Conservancy, now has a way to capture rainwater to replenish the ever-decreasing amount of groundwater. 

CVW recently met at the Rosemont Preserve with Frank Colcord of the Friends of the Rosemont Preserve and director of the Foothill Municipal Water District, and Arminé Sargsyan, Crescenta Valley Water District’s Water Resources and External Affairs specialist. The Rosemont Preserve is located behind the gate at the top of Rosemont Avenue. 

Colcord shared the completion of a bioswale at the base of the mountain of the Preserve. A bioswale is a wide, shallow ditch that is used to capture stormwater/rainwater runoff that also controls erosion. Rainwater is captured in this ditch before it gets to the Verdugo Wash and out to the ocean. 

“It’s about 250 to 300 acre of watershed,” Colcord said. 

He described that as relatively small for a watershed. 

“It’s probably a quarter of the size of the Pickens Canyon watershed but it is still significant,” he added. 

During a rainfall water that is not absorbed into the ground and by vegetation in the mountains will flow down into the bottom of the canyon to a ditch (bioswale) that was created in an open flat area.

“The rainwater comes down the canyon and when it rains really hard there are culverts off of Olive Avenue and Shield Street,” Colcord said. “The water that [currently]falls on Shield Street ends up in the street coming down the storm channel and empties into the [Rosemont Preserve].” 

The bioswale is a way to have that rainfall go into the groundwater supply. The bioswale is located on the boundary between the Preserve and the flood control debris basin.

Rainwater that goes into the Verdugo Wash flows into the LA River and then into the ocean. This water, due to century old water rights, belongs to the City of LA. Because of the bioswale some of that water is now being captured long before it hits the Wash. 

According to the Rosemont Preserve, this project includes improvement to the sustainability of local groundwater resources, improves functionality of this multi-use community space and provides the community with the opportunity to build local infrastructure. 

The stormwater capture and recharge (bioswale)will expand functionality of existing debris basins by enhancing stormwater retention and groundwater recharge capabilities and provide proof of concept for potential use at other debris basins, according to the Rosemont Preserve. 

A percentage of the water captured would end up in local CVWD wells. This would increase CVWD’s groundwater; the more groundwater available the less the agency would have to buy. 

During the drought the groundwater supply dropped requiring CVWD to purchase more water from outside agencies. The local area, as well as the State of California, is working to find ways to capture stormwater. 

“We’re in a better place now [with the recent increase in rainfall], but this will absolutely help infiltrate the aquifer and allow us to delay the need to purchase additional imported water,” Colcord said.

It takes about one to two years between the time rain falls on the ground at the Rosemont Preserve until it ends up in the basin where it can be pumped out. 

“And two winters ago we had 60 inches of rain up here; last winter we had 30 inches,” he added. 

The Crescenta Valley Water District partnered with the Arroyos & Foothills Conservancy on this project. 

“The District is grateful for the continued partnership of the Arroyos & Foothills Conservancy, the Friends of the Rosemont Preserve and the LA County Flood Control District in making CVWD’s first stormwater capture project a success. This nature-based solution is increasing groundwater recharge by allowing more time for water to infiltrate into the soil before entering the County storm channel. At the same time, our team is proactively pursuing Los Angeles County Measure W funding for a stormwater capture project at the CV Park. These innovative approaches reduce costs for our customers while recharging the Verdugo Basin, [which] supports water supply sustainability for the La Crescenta, Montrose, La Cañada and Glendale areas,” said James Lee, CVWD general manager. 

For those who would like to visit the Rosemont Preserve, on May 3 visitors are invited to join the Friends of the Rosemont Preserve committee members to “wander the trail.” It is advised to wear sturdy shoes. Rosemont Preserve is located at the intersection of Shields and Rosemont avenues. Parking is at Two Strike Park, 5107 Rosemont Ave.