South Prairie Creek
South Prairie Creek has been a focus area for the Pierce Conservation District over the past 9 years, due primarily to its importance for natural salmon fish production in the Puyallup River System. In recent years, the South Prairie Creek watershed basin has become heavily impacted by Japanese Knotweed, causing concern for both surrounding homeowners and conservation agencies due to its negative impact on important riparian habitat required for fish spawning and rearing. In 2010, the Pierce County Conservation District, in cooperation with the Pierce County Noxious Weed Control Board, began inventorying knotweed infestations located throughout the entire watershed in order to develop a strategic control plan.

Lower South Prairie Creek

A creek along the creek bed
In the summer of 2011, the district began removal of this highly aggressive invasive species utilizing a “top down approach,” starting control activities from the upper extent of infestation located along upper Wilkeson Creek and working downstream toward the confluence with the Carbon River.

All portions of the South Prairie Creek Basin, whether in public or private ownership, are threatened by the spread of knotweed. Allowing knotweed to continue to spread without treatment will ensure the long-term degradation of riparian habitat, establishment of vegetative monoculture, and an increase in water temperatures.

2012 Project Update
The district’s South Prairie Creek Knotweed Control Project experienced a highly successful 2012 summer treatment season. With the help of EarthCorps, a Seattle-based non-profit organization, and the district’s project partner Pierce County Surface Water Management, initial knotweed treatment on participating landowner’s properties was completed within the watershed. With 3 months of grueling work, crews were able to treat down to the mouth of South Prairie Creek, totaling the treatment of 144 knotweed infested acres. Although follow-up maintenance of past treated areas is needed, as well as more landowner participation in the project, this is a huge step in helping restore critical riparian habitat needed for fish spawning and rearing.

View a map of the Progress on the South Prairie Creek (PDF).
The Nisqually watershed (WRIA 11) is unique for its ecological, cultural and economic resources. It is the only watershed in the United States with its headwaters in a national park and its delta in a national wildlife refuge. The 1972 Washington State Shorelines Management Act recognized it as a “River of Statewide Significance,” and for more than 20 years it has had a strong history of conservation and stewardship. Despite impacts from timber, residential, and agricultural use, it remains one of the Puget Sound’s healthiest and least developed rivers.
Invasive knotweeds have been present in the Nisqually watershed for many years but only anecdotal information existed about their distribution and extent. In the spring of 2007, the following organizations came together to form a Cooperative Weed Management Area (CWMA) for the Nisqually River:
  • County conservation districts
  • The county weed boards
  • The National Park Service
  • Nisqually Land Trust
  • Nisqually River Council
  • Nisqually Tribe
  • Tacoma Power
  • U.S. Department of Defense
  • U.S. Fish and Wildlife Service
  • U.S. Forest Service
  • Washington State Department of Natural Resources
  • Washington State Parks

Upper mainstem of the Nisqually River

A winding creek with sandy banks and the mountains in the background
The group’s initial focus was to survey the entire river and develop a management plan to coordinate and maximize control efforts for knotweed. Although many of these partners had previously worked together on restoration projects, the knotweed control project was the 1st time that they collaborated for a watershed-scale weed control project. The Pierce County Noxious Weed Control Board (PCNWCB) initially served as lead entity for the project but in 2010, the project was transferred to the Pierce Conservation District (PCD).

Since the project’s acquisition, PCD has had much success in continuing knotweed control activities throughout the Nisqually River watershed. The lower mainstem of the river is floated each year with help from project partners including the Nisqually Indian Tribe, Tacoma Power, U.S. Fish and wildlife and the Thurston County Noxious Weed Control Agency.

View a map of the Progress on the Nisqually River (PDF).