Rio Hondo/Upper San Gabriel River Watershed Arundo Eradication Program

The Rio Hondo/Upper San Gabriel River Watershed Arundo Eradication Program will remove 48 acres of Arundo donax from the San Gabriel River and Rio Hondo at and above Whittier Narrows. Monitoring follow-up on treatment efficacy, missed invasives, and resprouts will continue past initial treatment for a total project duration of five years. Site surveillance will then occur on an annual basis for five years beyond the monitoring and retreatments.

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 this Arundo eradication in the San Gabriel River could provide an additional 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.