Bioswale & Rainwater Harvesting

About Us

The Rainwater Harvesting System and Bioswale project was created to promote stormwater retention and water conservation. 

Project Goals:

1. Collect rainwater to reduce the volume of potable water used for irrigation

2. Decrease stormwater runoff pollution going into Strawberry Creek

The project site was selected because of the centralized gutter system at the location, and because buildings and site are not historical, making them easy to modify.

Mission Statement:

We believe ESW’s projects should reflect a commitment to sustainability through education, innovation, and activism. 

Our project promotes sustainability on UC Berkeley’s campus by educating the public and modeling a pathway to a greener, more environmentally conscious future.

How It Works

Rainwater is collected from the Hearst Field Annex roof and captured in the rainwater harvesting tank. This water is used to irrigate the Annex’s lawn in place of potable municipal water. When the tank reaches capacity, overflow is directed to the bioswale. It then infiltrates into the surrounding soil, and prevents runoff from directly entering the sewer system. The bioswale protects the water quality of Strawberry Creek while also beautifying the Hearst Field Annex lawn.

After rainfall, the first few gallons of stormwater pass to a first flush diverter and all remaining water flows to the tank. Collected water is designated for irrigation use by the center strip of lawn sprinklers via one irrigation valve. When the tank is empty, a hydraulic back-up valve automatically switches to provide municipal supply to the sprinklers. A water level gauge is installed on top of the tank and a water meter is plumbed on the rain supply to monitor the accumulative rainwater used.

The bioswale contains a variety of native plants protected by mulch, with layers of soil and gravel to filter water that flows through the bioswale channel. 

This system handles an average of 50,000 gallons of water every year, with 15,000 saved and used for irrigation, and 35,000 treated by the bioswale.*

*These numbers were calculated by looking at rainfall patterns in Berkeley from 2000 to 2019. California has an extremely unpredictable climate and the amount of water processed by the system will fluctuate from year to year. Most years fall significantly above or below the calculated average rainfall. As rainfall rates become more variable due to climate change, green infrastructure projects like the Rainwater Harvesting Bioswale System will become more important to manage our state’s water resources.

Project Timeline

Bioswale & Rainwater Harvesting

2016 – 2017

The First Steps

Funding & Modeling

The project began in 2016, with a a $24,000 grant from The Green Initiative Fund (TGIF). The team created a 3D model of the tank components and met with campus facilities services, landscape architects, and botany experts for input about the project.



The Rainwater Harvesting system was installed. This included the redirection of the gutters, tank installation, and rewiring of the sprinkler system.

2019 – 2020

Bioswale Design

Design for the ancillary bioswale began. The team researched plants and visited a local nursery to compile a list of plants. Additional funding was acquired for educational signage.

February 2022


In February 2022, the bioswale was constructed. The team met with the landscaping, irrigation, and facilities team on campus to present a long-term maintenance plan to keep the bioswale healthy.
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A grand success!


Divya Vilekar

 Bioswale & Rainwater Harvesting Co-Lead

I am a third year studying Civil and Environmental Engineering, interested in green building and sustainable design. 

Julian Anatole Falagan

 Bioswale & Rainwater Harvesting Co-Lead

Liquid Gold Lead

In addition, the successes culminating in the Bioswale & Rainwater Harvesting would not be possible without a series of influential past project leads:

 Emma Tracy

Jocelyn Tsai

Derek Morimoto

Ashley Cowell

“Selfie time before we start working on our project!”

Thank you to all leaders, sponsors, and participants – and on to new journeys!