AWWA WQTC69490

For many utilities, an essential component of assessing source water vulnerability includes an evaluation of the impacts of changes in vegetative cover within source watersheds. In many parts of North America, forested environments are critical source water regions; in those environments, wildfires comprise significant land disturbances that greatly impact both water quality and quantity in headwaters. In 2003, the Lost Creek wildfire impacted the upper Oldman River Watershed in Alberta, Canada. It was one of the more severe recorded fires in the eastern slopes of the Rocky Mountains. Many aspects of streamflow and water quality were impacted and have been studied during five subsequent years of watershed recovery. The potential impacts of wildfire on drinking water treatment were assessed by collecting and evaluating a comprehensive data set describing the basic hydrology and water quality (turbidity, total phosphorous, total kjeldahl nitrogen, and dissolved organic carbon) from source watersheds with varying degrees of land disturbance associated with wildfire (unburned, burned, and post-fire salvage logged) over four years after the wildfire. Jar tests were conducted to investigate the wildfire and salvage-logging associated changes in water quality and quantity relative to unburned environments and their implications to drinking water treatment. The observed vegetation and land use impacts on water quality of the Oldman watershed in Alberta, Canada are representative of increasing pressures related to land use change in many regions of North America. Compared to unburned watersheds, the observed increased turbidity, TP, TKN and DOC levels observed in streams draining burned and salvage-logged watersheds present important economic, logistical and operational challenges for water suppliers, managers and regulators. The data show that such wildfire related changes in surface water quality can increase coagulant demand, sludge production and oxidant demand/fluence requirements; they also can increase public health protection challenges (potential increases in microcystins and DBPs). Accordingly, failure to manage and protect critical source water regions will have significant cost and compliance implications that will influence the long term sustainability of water management. Includes 21 references, tables, figures.