Help keep our Arboretum and Public Garden spaces open

Bubbles in the Waterway

Waterway Stewardship Learning by Leading Co-Coordinators pointing to the air bubbles created by the air-powered circulator in Lake Spafford.
Noreen Mabini and Karyn Utsumi, two members of the Waterway Stewardship Learning by Leading program, point to aeration in the Arboretum Waterway.

The Arboretum and Public Garden is adding two air-powered circulators to the Arboretum Waterway, one at Lake Spafford and one near the old boathouse. The reason for the circulators is to improve circulation and oxygenation of the water, which will help keep surface algae at bay and improve water quality. We also expect that, like last year, we will find cyanobacteria in the water at some point this summer or fall. We are monitoring for this following the guidance of the California State Water Quality Control Board. We hope that circulators will also help decrease this natural phenomenon.

Circulation has been found to reduce cyanobacteria blooms in similar water bodies. These air-powered circulators operate by pumping air through a diffuser near the bottom of the waterbody, resulting in the formation of plumes that rise to the surface and create vertical circulation cells as they propagate outwards from the aerator. This mixing of the water column disrupts the behavior of cyanobacteria to migrate vertically in addition to limiting the accessibility of nutrients. It may also promote favorable growth conditions for competing organisms.

The air-powered circulators are not adding water or anything other than air to the Arboretum Waterway. They are safe for fish and other aquatic organisms.


Air bubbles on the surface of the Waterway created by the air-powered circulator.
A closer view of the bubbles created by the air-powered circulator, pushing water from the bottom, to the surface of the Waterway and outward from the center.


You may be wondering about plans for the next portion of the Arboretum Waterway Maintenance and Improvement Project. Phase 1 of the project was completed in 2018 and can be seen from the east end of the Waterway (near downtown Davis) to the Redwood Grove. This area remains free of the typical smelly algae mats we used to see over the summer thanks to water circulation over the weirs and California native plants along the water edge. The UC Davis Arboretum and Public Garden has applied for a state grant that could provide funding for Phases 2 through 4 with matching funds from UC Davis. If funded, we hope to resume construction of the remaining phases of the project in 2022.