Invasive Water Chestnut: Tracking as a First Step to Eradication

Among the challenges faced by municipal stormwater management programs, the management of invasive flora and fauna often prove as challenging as any. In recent years, Fairfax County, among only a handful of Virginia jurisdictions, has discovered an invasive plant that threatens both County stormwater quality as well as the functionality of the stormwater retention basins designed to improve water quality over time. Commonly referred to as Water Chestnut, the invasive species, Trapa bispinosa, grows aggressively on the surface of wet ponds, developing a thick matting of vegetation on the surface and a stem structure that can grow up to 16 feet. Once established, water chestnut can effectively block sunlight from reaching a pond’s water column, depleting supplies of dissolved oxygen and significantly impairing both the water column and the pond’s natural ability for water quality improvement.

In a proactive effort to prevent the deoxygenation of pond ecosystems in the County, the DPWES Maintenance and Stormwater Management division has recently undertaken the daunting task of developing an identification, tracking, and treatment program to address the water quality threats this invasive plant species present.

Working with GKY, Fairfax County staff have initiated these invasive management efforts, with a focus on public education and outreach to pond owners and managers, as well as internal tracking and training material development for County and consultant inspection staff. This presentation will highlight the County’s efforts to date, and discuss future management tools aimed at increasing awareness of the management issues that water chestnut creates as well as the options available for long-term management of this invasive species.