Arroyo Seco Foundation
Here's the Latest for All Things Arroyo —

John Muir Remembers

Have you seen Tim Brick's dramatic monologue of the famed naturalist, "John Muir Remembers?" It's worth a look.

Arroyo Trails Open Again

Stay Safe! Stay Healthy!

It's been a wet year in the upper Arroyo watershed, so we are anxious to get up there to do some trout scouting. If you're interested in helping restore native trout to the Arroyo Seco, let us know!

Berkshire Creek

The Berkshire Creek Restoration in Hahamongna Watershed Park has now been completed. The Arroyo Seco Foundation is proud to be the co-sponsor of this Urban Streams Restoraton Program along with the City of Pasadena.

After a delay due to health precautions, the area is now open to the public again. We hope you will soon come to observe Berkshire Creek and how the project has improved habitat, flood protection and public safety in the southwest corner of Hahamongna Watershed Park.

All About Berkshire Creek

Welcome to Hahamongna Watershed Parking Lot

What kind of neighbor would destroy such precious streamzone habitat?

What kind of a city would let them?

Read the Full Story

Mayoral Candidates Square Off on Pasadena Environmental Issues

The Arroyo, climate change, the urban forest and other key environmental concerns were the focus of discussion at the Pasadena Central Libarary on Pasadena on Tuesday, January 14, 2020. The theme of the event was "How Green Should Pasadena Be?" The discussion surfaced significant differences among the candidates.

The Arroyo Needs You Now . . .

Support the Campaign to Protect and Restore a Natural Arroyo!

2019 Arroyo Appeal  2019 Highlights


Cleaning Up the Arroyo Stream

More than 120 students from Maranatha High School came to the Arroyo Seco in Pasadena during Thanksgiving Week in November as part of the Arroyo Seco Foundation's (ASF) Stream Team volunteer program. The two-day event was part of Maranatha's annual Thanksgiving community service program. An energetic crew of students and teachers removed invasive species from the stream just north of the mouth of the Arroyo Seco as it comes out of the San Gabriel Mountains.

Out with the Invasives!

Berkshire Creek Restoration Nears Completion

The construction contractor has been making steady progress on the Berkshire Creek restoration in Hahamongna Watershed Park since they began in September. Construction is now expected to be completed by the middle of January, 2020.

Construction Pictures

A cute little endangered least bells vireo came to Hahamongna recently to celebrate the 20th anniversary of this Arroyo Seco website. Let's all celebrate by renewing our efforts to protect and preserve wildlife.

Judge's Tentative Decision Prompts Big Dig Settlement Discussions

Superior Court Judge Jemse Chalfant delivered a wake-up call to County officials on Wednesday, June 19. The mesage came in a strongly worded tentative judgment in favor of the Arroyo Seco Foundation and Pasadena Audubon in their second lawsuit against the County Flood Control District's Big Dig sediment removal program behind Devil's Gate Dam in Hahamongna Watershed Park.

"We won the first lawsuit and achieved some of our goals," said ASF's Tim Brick. "But the County failed to listen to the community or to detail a suitable mitigation plan, so we went to court again. This time we expect the County to listen."

There has been progress in the settlement negotiations. The next hearing date has been set for April 30th.

Never Forget the Importance of Hahamongna

We have never opposed the County Flood Control District's sediment removal from Hahamongna Watershed Park. The Arroyo Seco Foundation has been urging the Flood District to do a slow, steady sediment management program for more than thirty years. The County's irresponsible delay of their mainentance responsibility has necessitated the Big Dig and compounded its negative impacts.

We only sought a safe, careful plan, but as the trucks begin to rolll and the grinders and excavator dig deep into the Arroyo Seco streamzone, it is now apparent that the Flood Control District has failed on that score too.

We urge those who love Hahamongna to not forget its importance and to redouble your efforts to help restore it for future generations.

For the past year more than 400 community scientists have documented how biodiverse this 300-acre jewel of the Arroyo Seco is by making as many observations of as many species as possible before the County erases our memory of its grandeur.

You can help! Visit Hahamongna Watershed Park and take your photos of life in the Watershed.

Learn More About:


Located at the foot of the San Gabriel Mountains where the mountainous watershed meets the urban plain, periodically floods roar into this basin. Bounded on the north by the mountains and Jet Propulsion Laboratory and on the south by Devil's Gate Dam, Hahamongna contains five unique habitat zones that only exist in alluvial canyons near the mountains. Most sites like this in Southern California have been destroyed.

Learn and help others see why it's important to help Save the Hahamongna Watershed, a key hub of the Arroyo Seco, by documenting all wildlife, plants, trees, and recreation including people, dogs and horses located within the park boundaries.

Big Spring Sale —
This Sunday!

The sages, shrubs, grasses and trees are exploding with life and color at Hahamongna Native Plant Nursery in the Arroyo Seco. We have more than 60 native species available to enrich your home or business. Come by and witness the botanical glories of our region and add a bit of nature to your home.

Open Saturdays & Sundays (9 am to 1 pm)
Hahamongna Native Plant Nursery
4550 Oak Grove Drive (@ Foothill)
Pasadena 91103
(626) 657-0392

Plants for Sale    |    Directions

Steelhead Used to Love the Arroyo

The Arroyo Seco is the most important stream on the Los Angeles River system for steelhead and trout because of its strategic location and fresh, cold water. Prior to 1920 steelhead migrated each year between the mountain watershed and the Pacific Ocean. Can you help bring them back home?

If you would like to get involved, send an email to

Native Trout in the Arroyo

Hahamongna Accountability Project Formed

Local residents and community organizations including the Arroyo Seco Foundation have formed a group of watchdogs to ensure that the County Flood Cotrol District fully complies with all their responsibilities in implementation of their Big Dig project.

We need your help again to Save Hahamongna!

How You Can Help

Hahamongna Before -
Don't Forget

The River Returns

It's been so dry in the upper Arroyo Seco Watershed for so long that most people have forgotten the power of the river! The recent storms did a lot to change that! The stream gauge in the Arroyo jumped from 1 cubic foot (cfs) or 7.5 gallons per second to one thousand cfs briefly on January 17 and a week later climbed up to 300 cfs before resting for a bit at 100 cfs. That should really open up the stream up there between Oak Wilde and Switzer's Camp for the fish and aquatic species.

Spring at Hahamongna Nursery

The recent rains have already had a wonderful effect on the plants at Hahamongna Native Plant Nursery. The plants are uncertain about whether it is Spring yet. Some think is is and are blossoming, while others are still relatively dormant.

We are now growing plants for the Berkshire Creek Project in Hahamongna that we are co-sponsoring with the City of Pasadena. We'll be reaching out to the community to make the project a grand example of community involvement and propagate more than 900 plants and many pounds of seeds for the habitat restoration component of the project.

The Arroyo Is Under Attack

Click on the pictures for a bigger image

View the Devastation

County bulldozers have invaded Hahamongna Watershed Park this month to destroy the most valuable habitat in our region. The fifty acre destruction zone is the outline of the massive Big Pit they want to dig where they will destroy habitat each year.

2018 was the 25th anniversary of Hahamongna Watershed Park, so it's time to look back on the history of the park and the meaning of Hahamongna.

Come Visit Hahamongna ASAP!

Alternate Visions

The bulldozers and trucks are lined up ready to destroy the most precious habitat and wildlife corriror in the west San Gabriel Valley.

Trout Scouting in the Arroyo

Fisheries biologist Ken Jarrett from Stillwater Sciences took a crew of ASF volunteers up the canyon to assess conditions for native fish.

Brown Canyon Dam — Then and Now

Paul Ayers unearthed these pictures of Brown Canyon Dam three and a half miles up the Arroyo Seco Canyon from the mouth of the Arroyo near JPL.

Big Push to Include Arroyo in LA River Planning

"It's like an arm on a body," Tim Brick explains on KABC-TV.

Senator Portantino Moves to Include the Arroyo

Senator Anthony Portantino has introduced legislation to add representation for the Arroyo Seco in the Upper LA River and Tributaries Working Group.

Protecting Hahamongna: Big Dig Update

ASF and Pasadena Audubon are still working with Supervisor Barger and the County Department of Public Works to reduce the impacts of the Flood Control District's sediment removal program at Devil's Gate Dam. In November Supervisor Barger push through a motion to scale back the program in November. That was a big step, but there are still some unresolved problems with the Big Dig. We hope to have more news about the future of Hahamongna for you soon.

Help Grow

Would you like to be part of the Hahamongna Nursery Team? You can learn about native plant identification and how to propagate and tend California's most venerable and spectacular plants. They are a precious legacy for future generations. Send an email to


The battle to Save Hahamongna has been a long and bitterly fought one. Click on the link below to review the updates on the campaign against the Big Dig and witness citizen power in action.

Thank you for your support and congratulations!

Native Fish in the Arroyo — Can We Bring Them Back?

The answer, of course, is Yes! While there are numerous barriers and problems, the conditions in many parts of the Arroyo watershed are excellent for native fish including Rainbow Trout and Steelhead. ASF's meeting last July at the Pasadena Public Library generated a lot of interest and discussion about native fish.


One Arroyo

The Arroyo Advisory Group reported their progress to the Pasadena City Council on February 5th. The City Council approved $100,000 to establish a foundation that will raise funds for Arroyo Projects, such as a major trail improvement that will provide greater access and link together he various parts of the Arroyo in Pasadena.

Want to see a beautiful native plant garden? Check out the one this crew planted at Linda Vista Library, 281 Bryant St, Pasadena, CA 91103.

Arroyo River Parks
Restoring a Living River

Here's an innovative approach for the future that will restore the Arroyo Seco by integrating the river into the parks and the parks into the river.

Why Not a Complete San Gabriel Mountains National Monument?

Now that the Trump Administration review of National Monuments seems to be winding down, it's time to again raise an issue about our local monument. By a mysterious process that no one will explain, the Arroyo Seco and the southwest corner of the Angeles National Forest were eliminated at the last minute when the San Gabriel Mountains National Monument was announced. It's a shame because many of the most treasured and historic sites in the San Gabriel Mountains are contained in the territory that was not included.

Congresswoman Judy Chu has now proposed legislation that would expand the boundaries of the national monument to include all of the treasures of the Angeles National Forest.


Arroyo Canyon Project

The Canyon Project is an innovative program to improve water resources and environmental conditions in the Arroyo co-sponsored by the Arroyo Seco Foundation and Pasadena Water & Power Department. As the result of a legal challenge, the project is now undergoing further environmental review.