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Harvest Season, Wetland Style
Author: Jill McGrady, PhD
Autumn brings thoughts of changing leaves, colder temperatures, and for farmers across North America, harvest season. For the ecologists in our San Diego office, the harvest season means something a bit different - a trip up the I-5 freeway to visit our constructed treatment wetland at the world-famous Del Mar Fairgrounds. Designed by Great Ecology and Fuscoe Engineering, the 1-acre wetland system functions similarly to natural wetlands with the purpose of treating wastewater from the Fairgrounds using a variety of physical, chemical, and biological processes. These include sedimentation, filtration, precipitation, sorption, microbial decomposition, phosphorus and nitrogen transformations, and plant uptake. But what does harvest season have to do with a treatment wetland?
The wetland plants within the system, primarily cattails and bullrush, take up nutrients from the Fairground’s equine operations and incorporate them into their aboveground biomass. By conducting an annual harvest of the vegetation, all the nutrients sequestered in the vegetation are effectively removed from the wetlands. This allows the system to "reset" and continue operating efficiently as the vegetation resprouts and is fueled by continued nutrient uptake until next year's harvest.
We're excited to share that Great Ecology just completed the first harvest of the wetland vegetation at the constructed treatment wetland, which included hand pruning of all cattails and bulrush plantings, rafting cuttings to the shoreline (using surfboards!), and hauling the nutrient-rich green waste to the Miramar landfill. We've already seen the wetland vegetation begin to resprout following the harvest, and will continue to monitor the regrowth as part of our ongoing management and maintenance of the system.