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Western Wildfires Put Water Systems at Risk of Pollution
IJC admin | 2017/10/18
By Michael Mezzacapo, IJC
2017 has been another intense year for wildfires in the western US and Canada, placing water infrastructure in the crosshairs. After many previous years of drought, last winter brought above-average rain and snowfall for much of the West. Although the precipitation was helpful to resupply the mountain snowpack and drinking water reservoirs, it helped spur explosive spring growth of vegetation which was quickly dried out by intense summer heat and drought.
The Eagle Creek wildfire burning in the Columbia River Gorge. Credit: US Forest Service
Fires like the recent Eagle Creek fire in the Columbia River Gorge on the border of Oregon and Washington have significantly impacted community resources and destroyed tens of thousands of acres of forest. The increase in fires is worrisome, especially for water utilities. In Oregon, the city of Portland’s water supply, Bull Run Reservoir, saw fire damage in large sections of forest in its watershed. As the population of western North America continues to expand into forested areas, there is a greater risk of damage to public and private infrastructure from extreme wildfires. A recent study by the US Geological Survey (USGS) finds that erosion rates significantly increased in areas burned by wildfires. This causes more sediment to enter the water supply, impacting water treatment systems and aquatic ecosystems. According to Joel Sankey, USGS scientist and lead author of the study, “at least 65 percent of the water supply in the West originates in watersheds with fire-prone vegetation.”
A graphic showing how increases in temperatures impact wildfire risk. Credit: US Forest Service Missoula Fire Sciences Laboratory
Climate change is another factor that adds fuel to the proverbial fire. A warming climate changes the hydrological cycle, intensifying fires. Scientists like John Abatzoglou of the University of Idaho study the link between climate change and wildfires. According to Abatzoglou, there are challenges to understanding the role climate change plays in increasing the number of wildfires. Many factors influence fires, including poor land-use practices, lack of resources, outdated fire suppression tactics and rising temperatures from human emissions. 2017 was an unusually hot summer in the West with cities like Quilayute, Washington, in the typically rainy and cool Pacific Northwest, setting a record for the second-highest temperature of all time at 37 °C (98 °F). Since 2000, the West has repeatedly seen above-average fire seasons, and it’s not expected to slow anytime soon. Columbia University bioclimatologist Park Williams thinks that by the 2030s, it’s very likely that future forest fires will dwarf those seen today.
Credit: Bruce M. Kilgore, National Park Service
Historical fire suppression tactics have contributed to the increase in frequency and intensity of forest fires. Suppression of naturally occurring blazes may actually increase wildfire risk. The goal of 100 percent suppression in the US was initiated after major fires in 1910, where three million acres of forest burned in Montana, Idaho and Washington in just two days. Conservationists and natural resource managers wanted to protect commercial timber harvesting and newly created national forests. Events like the 1910 fires cemented early policy which aimed to achieve two objectives: prevent and suppress all fires.
In the 1960s, scientists began to have a better understanding of fire and the essential role it played in the health of western forests. As early as the 1970s, the US Forest Service began to shift focus from total fire prevention to a “let-burn” policy, allowing some fires in wilderness areas to burn untouched. British Columbia adopted a similar official policy in 2010 of “monitoring and managing” wilderness area fires where appropriate. But the line remains blurred between when fire is beneficial and when fire is destructive.
This graphic shows a map of the area of wildfires inside and outside WUI areas, along with a graph detailing the percentage of burned areas in WUI by state. Credit: Schoennagel et al.
Western cities are scrambling to keep pace with population increases. Settlements are expanding rapidly into forested areas or Wildland Urban Interfaces (WUIs), the transition zone between unoccupied land and human development. Human development in western US cities now covers more than 165,000 square miles (427,348 square kilometers) and the wildfire risk to drinking systems isn’t going unnoticed. A 2014 workshop by the Water Research Foundation and Canadian Water Network looked at wildfire impacts on water supplies and potential mitigation. Impacts on streams, public water supplies, and overall water quality can extend far downstream from fires and damage may persist for many years. Important climate and geographic factors including topography, soils and the timing and amount of precipitation events after fires are key factors which can cause changes in water quality. Furthermore, variability in these factors makes their effects difficult to predict impacts.
After trees and grasses burn, there is less organic material left to absorb moisture when it rains, and some plants release a waxy substance when burned which can create a water-repellent coating on burn areas that increases erosion and sediment transport. Intense storms flush silt and other debris from the fires into rivers, reservoirs, and ultimately into municipal water-treatment facilities, slowing the treatment process. Water treatment plants may not be designed to handle the increases in turbidity, dissolved organic carbon, nutrients, or heavy metals after wildfires. If wildfires occur within the immediate boundaries of water supplies, it may reduce or halt treatment capacity.
A graphic showing forests in need of treatment to reduce catastrophic fire risk, assessing the ‘departure’ of today’s forests from historical conditions and defining the needs for ecological restoration. Credit: Erica Simek Sloniker, The Nature Conservancy
It’s difficult to predict future fire events and their impacts on the northwestern transboundary basin. The basin shares vulnerabilities with other western communities. Ryan Haugo, a Washington-Idaho forest ecologist, cites “poor management of western forests over the past century that has broken the natural link with fire, leaving forests vulnerable to uncharacteristically large and destructive fire and insect and disease outbreaks.”
Large fires will inevitably place water infrastructure at risk, such as the 2002 Hayman fire in Denver, Colorado, which cost Denver nearly $238 million in damages and restoration costs, or the 2009 fire in Lillooet, British Columbia, which caused the town to seek alternative sources for its drinking water supply. The US Environmental Protection Agency and Water Research Foundation recommend that water managers conduct wildfire hazard assessments in their watersheds to identify risks and take appropriate steps to reducing the effects of wildfire. Various pre- and post-forest management approaches, such as prescribed burns or creating residential defense zones, reduce the risk of wildfire and can minimize the potential effects on drinking water quality and quantity.
Michael Mezzacapo is the 2017-2018 Michigan Sea Grant Fellow at the IJC’s Great Lakes Regional Office in Windsor, Ontario.