Risks to water quality can disrupt the ability of water suppliers to deliver clean and safe drinking water. In addition to earthquakes, these risks can come from wildfires, volcanic eruptions, resource supply chain disruptions, accidental contamination, severe weather, and climate change impacts. Water quality impacts will vary depending on the severity of the risk. Fortunately, Forum members have developed mitigation strategies for their water systems to reduce the potential impacts.
Wildfires. A wildfire that burns several thousand acres could increase turbidity, add nutrients and metals, and other chemicals to the water as airborne particulates, and through runoff from the burned slopes that drain into reservoirs. As the Puget Sound wildfire risks and frequency increase with climate change, this is an important issue to address.
Volcanic eruption. If Mount Rainier erupts, large areas of suburban Pierce and southern King County could be affected by lahars (or mudflows). The entire region could be affected by tephra (rock fragments) and ash from an eruption of Mount Rainier or Glacier Peak.
Resource supply chain disruptions. Resource supply chain disruptions can be caused by transportation problems and issues at the chemical supply source for treating water. The primary chemicals of concern used in the water treatment process are coagulants, pH adjusters like soda ash, and chlorine. Many utilities keep up to 30 days of chemical supply in-house; however, utilities are not always fully stocked due to seasonal variations in demand and management of chemical shelf-lives.
Severe weather. Severe adverse weather events can cause treatment facility failure, pipe and equipment damage, supply chain disruption, and staffing issues. Floods and landslides can increase turbidity in local waters and damage critical transportation and facility infrastructure. Snow and ice storms can prevent access to a utility’s facilities for several days or more. Utilities with groundwater options are more resilient to these risks, since groundwater is generally unaffected by severe adverse weather, with the exception of long-lasting power outages.
Accidental contamination. If chemicals other than those designed to treat drinking water reach the water supply, these chemicals could result in persistent environmental contamination. Chemicals of concern are oils, gasoline, and related chemicals. The closer the chemicals are to the drinking water supply intake, the higher the risk.
Climate change. Climate change is projected to alter the water cycle, which may greatly reduce water supply availability. Climate change impacts are likely to be similar throughout the three-county region. There is a strong correlation in streamflows in the five major rivers that are the main sources of existing and future surface water supplies.