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Eco-Friendly Fountains

Posted On September 23, 2019 | 14:23 pm | by jonathank | Permalink
New UV light filters protect water wildlife and preserve historic garden

By Jonathan Kavalier

Ducks, frogs, toads, birds, dragonflies, and several species of turtles enjoy the watery oases in our gardens, most of which Beatrix Farrand designed and implemented. Recently, four new ultraviolet light filters were installed in garden fountains to ensure better environmental stewardship and protect wildlife as we preserve Farrand’s masterpiece. By conservative estimates, we anticipate water savings of over 280,000 gallons and a reduction of 500 pounds of chlorine per year. 

There are 12 fountains on the property, all designed so fresh water constantly flows into them and eventually runs into the storm drain system after reaching the overflow level. Now, 100 years after Farrand began planning the Dumbarton Oaks Garden, we have made changes to conserve water and generally increase the sustainability of garden operations.

In 2017 and 2018 we retrofitted several fountains with recirculating systems as part of the stormwater project, and this has certainly reduced fountain water use. But recirculating fountains are prone to algae blooms, so we installed chlorinators to maintain clear water by injecting chlorine into the fountains.

Due to the prevalence of wildlife in the gardens, for the past year we have used chlorine only in the small fountains that don’t typically contain animals. We have regularly dumped and cleaned the larger fountains our wild residents enjoy. Of course, this dumping reduces the water savings we should be realizing.

So the Gardens and Grounds Department set to work researching a solution. We settled on ultraviolet light filters, fairly common devices in koi ponds and fountains. A UV bulb sits in a sleeve in line with the water pump, and as water passes, the light kills single-celled organisms such as algae. Single-celled algae causes freshwater bodies to turn unsightly green, brown, or red. Anything large enough to pass through the sleeve won’t be killed. (Luckily the fountains at Dumbarton Oaks do not have a problem with larger stringy or mat-forming algae.)

We installed ultraviolet light filters in the Pebble Garden, Fountain Terrace, Lovers’ Lane, and Ellipse fountains this July. Already, the filters have succeeded in reducing algae blooms, and we are testing new methods to remove the leftover debris. Ultraviolet light filtration is eco-friendly and low-maintenance. Even with annual replacement costs for the bulbs, the garden saves money on labor and chlorine.

And perhaps most importantly, we are providing better habitat for our wildlife. This can have the indirect benefit of helping us reduce pesticide use in the gardens by promoting a healthy environment for beneficial insects and other predators to live and breed in. We are responsible for stewarding Beatrix Farrand’s iconic garden design while integrating modern horticultural and sustainability best practices. The new ultraviolet light filters greatly facilitate these efforts.


Jonathan Kavalier is Director of Gardens and Grounds at Dumbarton Oaks. Photo by Elizabeth Muñoz Huber, Postgraduate Digital Media Fellow.