Rio Hondo/Upper San Gabriel River Watershed Arundo Eradication Program

Location: Los Angeles County

Project Type: Restoration

Status: Current

Cost: $2,400,000

Funding Gap: $1,430,000

Area Affected: 45 acres

Project Footprint: 14.5 stream miles

Assembly District: 41, 48, 49, 55, 57

Senate District: 22, 25, 29, 32

Congressional District: 27, 32, 38, 39

Project Lead/Grantee:
Council for Watershed Health

The Rio Hondo/Upper San Gabriel River Watershed Arundo Eradication Program will remove 80 acres of Arundo donax and coexisting infestations of several other invasive plants from the San Gabriel River and Rio Hondo at Whittier Narrows. Monitoring for treatment efficacy, missed invasives, and resprouts will continue past initial treatment for a total project duration of five years.

The San Gabriel River serves as the primary water source for many cities along the river through recharge of the Upper San Gabriel and the Central groundwater basins.  Arundo transpires water at a much higher rate than locally-native vegetation and Arundo control in the San Gabriel River could add as much as 1,000 acre-feet/year of water to the groundwater supplies (Giessow, et al. 2011).  Rio Hondo, though part of the LA River Watershed, runs parallel to the San Gabriel River through the Whitter Narrows, and popular recreational destination with preserved riparian and upland sage scrub habitat Removing invasive such as Arundo from this stretch of the Rio Hondo and San Gabriel Rivers will help to restore the Whittier Narrows area to natural habitat, increasing water supply and improving ecosystem functions.