Join us at Hahamongna Native Plant Nursery in Pasadena on Saturday, January 17, 2026 for a free illustrated presentation about aquatic life and water conditions in the Arroyo Seco watershed.

Speaker: Matt Drenner, PhD, Senior Fisheries Biologist, Stillwater Sciences.

 

Dr. Drenner will discuss streamflow in the Arroyo Seco, water quality, and the status of aquatic life such as rainbow trout. His presentation will be illustrated with maps and photographs.

Date: 11 am till Noon, Saturday, January 17, 2026

Location: Indoors at Hahamongna Native Plant Nursery, in the Hahamongna Watershed Park, 4550 Oak Grove Drive, Pasadena (Follow the signs in the park).

Cost: Free Admission. Light refreshments offered.

Note: This event will be indoors and seating is limited. Registration

is encouraged to assure there will be enough seats.

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Register Here: 

Arroyo Seco Lecture at 11 am on January 17, 2026

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News: Streamflow Monitoring in Arroyo Seco Continues 
 

(PASADENA, CALIF.)-- A multi-year study of streamflow conditions, water quality, and aquatic life in the Arroyo Seco was concluded in August (2025) with recommendations that streamflow should be enhanced by removing human-made barriers.

 

The recommendation includes giving further consideration to removing Brown Mountain Dam, which is located in the upper Arroyo Seco. The study also recommended that water quality continue to be monitored, and that fish habitats continue to be evaluated.

 

The study—known as the Streamflow Enhancement Program for the Arroyo Seco-- was managed by Arroyo Seco Foundation of Pasadena with evaluations performed by Stillwater Sciences. The program was funded by a grant from the California Wildlife Conservation Board, with additional support from Accelerate Resilience Los Angeles and the Rose Foundation.

 

Program Manager Robert Kurkjian, Ph D, described the completion of this program not as an end, but rather as a first step toward long term sustainable management of the stream and ecosystem. “The Arroyo Seco is an important water resource and an environmental treasure, and its health requires our ongoing stewardship,” said Kurkjian.

 

One part of this stewardship, according to the recommendations of the study, is the continued monitoring of water quality in the Arroyo. In furtherance of this recommendation, the Arroyo Seco Foundation will continue to monitor streamflow and water quality in the stream by leading groups of citizen scientists on hikes into the region.

 

These citizen scientists observe trout populations and record water quality data and water conditions. Data is uploaded into a Geographic Information System (GIS) map of the Arroyo Seco watershed and made available to the public on the website of the Arroyo Seco Foundation at www.ArroyoSecoFoundation.org

 

Streamflow barriers are a concern because they impact water quality, restrict water flow, impact the ability of fish to migrate throughout the stream, and alter its ecology, says Kurkjian. These barriers then often result in fish morbidity when the fish become trapped and are unable to migrate up or downstream.

 

The primary fish population of the Arroyo Seco affected by these barriers is a species of rainbow trout. The study located and assessed 12 barriers to streamflow in the Upper Arroyo Seco, in addition to the prominent Devil’s Gate Dam and Brown Mountain Dam.

 

The importance of Arroyo Seco Foundation’s work has been widely recognized and has been featured in the Los Angeles Times, Environmental Monitor Magazine, and other periodicals. 

 

The Arroyo Seco is a vast geographic area in the Greater Pasadena area that is part wilderness, and part urban. It is home to the Arroyo Seco Stream and includes the region north of the NASA Jet Propulsion Laboratory, which is known as the Upper Arroyo, as well as the region that is home to the Rose Bowl. The portion of the Arroyo Seco Stream that passes the Rose Bowl has been channelized in concrete.

 

“The Arroyo Seco watershed is a local treasure and significant ecological resource,” says Kurkjian. “We need to preserve it for future generations”