Paddle with a Purpose: Water Chestnut Management in Upper Bucks County

The following article was written by Meghan Rogalus, Watershed Specialist with the Bucks County Conservation District and was originally included in the Spring 2020 edition of the "Tracking Invasive Species with Pennsylvania iMapInvasives" newsletter.

Pictured above: At the start of each day of 'Paddle with a Purpose', Meghan Rogalus shows volunteers distinguishing characteristics of water chestnut to help them identify the invasive plant in Lake Towhee. Photo provided by Meghan Rogalus.

Lake Towhee is a 50-acre impoundment at the center of a long-term Eurasian water chestnut (Trapa natans) management effort in Bucks County. The lake is the centerpiece of the 552-acre Lake Towhee County Park and outlets to Kimples Creek, which drains to the Tohickon Creek and Lake Nockamixon, Bucks County’s largest lake and focal point of Nockamixon State Park.

Eurasian water chestnut is an aquatic invasive plant that impacts lakes by quickly covering the water’s surface, forming dense mats that block sunlight. It also competes with native vegetation for space and nutrients and disrupts the aquatic food web and habitat structure. This plant dramatically impedes recreation because its dense mats clog boat motors and can make paddling difficult. Spiny seedpods pose hazards to swimmers’ feet and even boat trailer tires.

Because water chestnut is not native to the United States, our native wildlife cannot keep the population in check. The plant also spreads rapidly because it has multiple means of reproduction – it is an annual plant that primarily spreads by seed and also reproduces from small plant fragments. Once a population is established, water chestnut management requires a long-term effort. After plants flower annually in late June, they produce about 10-12 seedpods, each of which can remain viable on a lake bottom for up to 12 years!

Eurasian water chestnut was first documented on Lake Towhee in July of 2009. By that time, it had already spread to over half of the lake. Since August of 2009, the Bucks County Conservation District (BCCD) has coordinated an annual event branded ‘Paddle with a Purpose’ and partnered with the Pennsylvania Department of Environmental Protection, Nockamixon State Park, and Delaware Canal State Park.

Pictured above: Volunteers work from boats to pull water chestnut plants from Lake Towhee to prevent its spread to other locations by fragmentation. Credit: Ashlin Brooks

From 2010 on, the event has been timed between mid-June and mid-July to remove plants before the seeds mature. During the event, volunteers are educated on plant identification and impacts, and then paddle (in canoes or kayaks) or slowly motor to different sections of Lake Towhee to pull as much of the plant from the lake as possible. Some volunteers work with BCCD staff on shore to assist boaters with unloading their quarry. BCCD staff then haul the plant material to a pre-approved composting site.

Pictured above: Volunteers paddle back to shore with bags full of water chestnut where they are met with help to transfer the bags to a BCCD pick-up truck for transfer to an approved composting location. Credit: Amy Jewitt

This event started small with only about 10 participants, but has steadily grown in support to an event with over 75 annual participants. One key factor to the success and growth of the event was primarily the strength of the partnership between the county-level organizations and the state agencies. All were committed to preventing an unchecked spread of water chestnut to Lake Nockamixon.

Another major component was the loyal and consistent contribution of local volunteers who returned year after year to assist with the event and help spread the word. Volunteer recognition and appreciation, including a satisfying lunch after a hard half-day’s work, played a key role in developing this following.

One consistent limitation to the event’s capacity for more volunteers has been a limited number of boats available for volunteers who did not have their own. However, the recent addition of Delaware Canal State Park as a partner for ‘Paddle with a Purpose’ provided a significant boost in equipment capacity. Educators Katie Martens and Gabie Lent have brought a DCNR truck and trailer with kayaks, paddles, and PFDs for up to 20 volunteers at a time.

The iMapInvasives program has been instrumental in helping BCCD document the collaborative effort of volunteers and watershed partners in managing water chestnut. In particular, the ability to delineate ‘Searched Area’ and ‘Treatment Area’ polygons in the iMapInvasives database has given the BCCD the ability to document the extent of the area covered each year. In the two years that BCCD has delineated these areas in the online mapping platform, we’ve seen incremental progress in pushing the stand of water chestnut “uplake”.

BCCD has also been monitoring the Kimples Creek watershed and utilizing the iMapInvasives mobile app and the ‘Water Chestnut Chasers Challenge’ to document presence/absence of water chestnut in the drainage area up and downstream of Lake Towhee. We are grateful for the way the app supports our monitoring efforts in the field.