Municipalities and Their Watersheds

Many cities around the county have recognized the need for forest conservation as a means of source water protection. In Seattle, the city elected to raise water rates to finance watershed management activities in its source water watershed, the Cedar River watershed. Salem, Oregon relies on water from the North Santiam River watershed. High turbidity source water flowing from the watershed to Salem’s treatment works forced the city to use alternate treatment technologies and increase chemical usage. High technology companies served by the Salem Public Works Department became concerned about the chemical usage because of their very specific water quality requirements. As a result, Salem entered into an agreement with the US Forest Service specifying how the national forests in the watershed will be managed to prevent continued issues with turbidity during periods of peak flow. In both of these cases, the cities’ source watersheds are relatively distant, forested mountain watersheds.

There are clear linkages between water quality and the cost of water treatment. A number of studies show measurable, statistically significant changes in the cost of water treatment as a result of source water quality degradation. There is also an intuitive linkage – even where we cannot measure or isolate the impacts of declining water quality on treatment costs, we know intuitively there is an impact; this linkage was explicitly acknowledged in the 1996 amendments to the Safe Drinking Water Act, which specifically pointed to source water protection as the first barrier to pollution of drinking water supplies.

Overall impacts of source water quality on the cost of water treatment vary by the current treatment requirements and practices of a water utility. For example, New York City operates under a filtration waiver from EPA; degradation of water quality to the point where filtration would be required would cost the city billions of dollars in new treatment costs. This is not the case in the Delaware River basin, where water treatment facilities do not have filtration waivers. Here, changes in treatment costs may increase more gradually over time, typically as a result of increased chemical costs (coagulants, disinfectants, pH adjusters, etc.).

In 2002, the Trust for Public Land and the American Water Works Association conducted a study of water suppliers to determine the status of different system’s watersheds, treatment works, and treatment costs. This study resulted in some clear indicators of the relationship between forest cover and water treatment costs. Forest cover in source water watersheds explains approximately 50% of differences in treatment costs. In addition, as forest cover increases, treatment and chemical costs decrease: for every 10% increase in forest area up to 60%, there is a 20% decrease in costs.