Fernhill Natural Treatment Wetlands

Science Center Objects

The amount and type of algae in the Tualatin River affect the river’s water quality and ecological health, as well as its value as a recreational resource. As a relatively new source of summertime flow to the upper Tualatin River, discharges from the Fernhill Natural Treatment System (NTS) have the potential to enhance or degrade downstream water quality. Discharges of low nutrient concentrations and a dose of beneficial algae could enhance downstream river conditions, but releasing an innocula of cyanobacteria could also initiate a harmful algal bloom downstream. Use of the NTS, therefore, represents an opportunity to improve and manage algal conditions and the ecology of the Tualatin River, above and beyond the avoidance of releasing any potentially harmful discharges.

Tualatin map

Tualatin River Basin synoptic sampling sites.

During the early years of operation of the Fernhill Wetlands Natural Treatment System (NTS) and its 20-acre lake, monitoring of algae in the wetlands, its discharges, and the downstream river is helping to better understand the effects of wetland operations and how wetland processes, throughput, residence time, wetland plant species, and other factors and treatments affect the quality and algal species composition in wetland discharges.

The objectives of this study are to:

  • Identify and document the composition and size of the algal community in the Fernhill Wetlands NTS over a range of summertime conditions, as well as any changes to the downstream algal community that result from NTS discharges, and
  •  Assist District staff in understanding dissolved-oxygen budgets in the NTS, identifying threats to water quality and the algal community in the NTS and downstream in the Tualatin River, and provide technical expertise to help District staff find solutions and adapt NTS operations to avoid such threats and optimize the production of beneficial algal populations in NTS discharges.
NTS map

Fernhill Natural Treatment Wetlands, Tualatin River Basin, Oregon.