Upper Arroyo Seco Watershed Enhancement

Upper Arroyo Seco Watershed Enhancement

Pasadena’s water rights to the Arroyo Seco date back to the early 1900’s when water was diverted from the stream for domestic use. Over a century later, Pasadena continues to rely on this valuable local resource for water supply. Since surface runoff feeds the Arroyo Seco, it is clear that we need to protect the watershed to ensure the health of the stream. As part of this effort, PWP has developed the Upper Arroyo Seco Habitat Enhancement Plan (HEP). This plan will support the City’s goal of improving habitat functions and values in the City-owned open space within the upper watershed of the Arroyo Seco.


Phase 1: Habitat Restoration at Behner

PWP is implementing an initial phase of the HEP which involves habitat restoration of an area located just north of the Behner Water Treatment Plant along the Gabrielino Trail in the Hahamongna Watershed Park. The focus of this effort will be on removing non-native vegetation, allowing native vegetation to recover.  PWP is partnering with the Outward Bound Adventures youth group and seeking additional support from community volunteers.

Our first community event to kick-off the restoration effort at Behner Demonstration Site was held on November 16, 2019. An enthusiastic group of Outward Bound Adventures youth and community volunteers made great headway in enhancing this open space for the enjoyment of the park's visitors and for the benefit of the watershed.

Our efforts are on-going, and include:

  • A presentation to the City’s Urban Forestry Advisory Committee on December 11, 2019 for permission to remove a group of non-native sugar gum (eucalyptus) trees. Removal of these trees will allow the native, local plant habitat to reestablish in the demonstration area and is considered an important step for habitat restoration. UPDATE: Tree removal was completed May 2020.
  • Continued collaboration with OBA - A PWP-led tour in February 2020 introduced the youth group to the network of facilities that the City maintains for water supply, and highlighted the important link between watershed stewardship and protecting our water resources.
  • A planned workshop for community event leaders on the goals of the HEP
  • A presentation of PWP’s habitat enhancement plans for the Arroyo Seco to the City’s Hahamongna Watershed Park Advisory Committee was given in September 2020.
  • Stay tuned for future community events to continue restoration efforts for the Behner Demonstration Site and the greater Arroyo Seco watershed!

Visit our Events & Workshops page for upcoming volunteer opportunities.