First-ever 'water mower' helps clear invasive plants

Water mower operating

The wetlands of Nepal’s Chitwan National Park are being overrun by a menace: Eichhornia crassipes. Also known as water hyacinth, this flowering plant spreads so explosively that it smothers native plants and chokes up lakes, causing trouble for both people and animals. To clear these pesky propagators and other invasive plants from the wetlands, WWF and a cadre of engineers have built the first-ever water mower.

Built from 80% scrap metal and powered by two motorcycle engines, this crafty contraption floats atop several industrial-sized plastic drums, scooping up unwelcome weeds on a conveyor belt as it chugs along. And it means business: The mower can carry up to a ton of organic waste at a time!

Water mower illustration© RICHARD BORNEMANN/WWF-US


1 First conveyor belt
2 Motorcycle engines
3 Brakes
4 Plastic drums
5 Solar panels
6 Second conveyor belt
7 Dumping platform


Initial tests of the water mower prototype took place on Beeshazaar Lake, an oxbow lake in Chitwan National Park. The 7,900-acre wetland provides critical habitat for many of Nepal’s rare and endangered species, including Bengal tigers, gharials, and greater one-horned rhinos.

The water mower is a cheap way to clear overgrown wetlands, and much faster and easier than manual labor. Now, WWF is building a second, more user-friendly model that will be used to scale up efforts throughout the cluster of nine lakes in Pokhara Valley, at the foot of the Himalayan mountain range.

Why “mow” a lake? As invasive plants grow and spread, they cover and block other plants’ access to light and water, killing native flora that aquatic species and wildlife depend on. As they decay, they also clog wetlands and impact water flow, which can threaten the functioning of ecosystems and have long-term negative effects on biodiversity.

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