Threats to Water Quality
EWEB conducted an initial risk assessment back in 2000, as well as a nonpoint source pollution prevention assessment in 2006. We generally group threats into three broad categories: agriculture, forestry and development, or the human built environment. EWEB conducts various projects and assistance programs designed to minimize or mitigate these threats.
In the McKenzie watershed, development along the river has resulted in over 200 structures being built in the floodway, and nearly 1,200 in the 100-year floodplain. While drinking water quality of the McKenzie River is currently excellent, human activity and development within the watershed poses significant challenges for the long-term protection of this currently clean and safe drinking water source. Development along rivers often leads to loss of riparian vegetation, increased fertilizer and pesticide use, increased impervious surface area and storm water runoff, contamination of water from septic systems, and hazardous materials spills. The closer to the river, the more likely pollutants are to reach the water via runoff, especially during rain and storms.Link to page
In the McKenzie watershed most agricultural land is located along the valley floor in close proximity to the river. Numerous USGS studies show that pesticides and nutrients occurred more frequently and at higher concentrations at monitoring sites located in agricultural areas. Drinking water sources degraded by agricultural nonpoint sources of pollutants increase raw water treatment costs and pose a risk to public health.Link to page
The McKenzie watershed is comprised of 88% forested land, with a mixture of private, state, and federally owned lands. Forested watersheds, like the McKenzie, produce better water quality than any other surface water source. In addition, a study by the Trust for Public Land found that for every 10 percent increase in forest cover in a source area watershed, water treatment and chemicals costs decreased by approximately 20 percent (TPL, 2002). However, forest management activities that may adversely impact downstream water quality include: the use of chemical applications for stand treatment; road building and failures; and various timber harvest techniques. The greatest risk to drinking water from industrial forest management activities is due to aerial application of pesticides because of drift, wash-off, and erosion processes.Link to page