Oregon’s Water Supply at Risk: Assessing Natural, Built, and Social Hazards for Improved Risk Management

Abstract Water suppliers face multiple stressors including natural hazards such as floods and wildfires, aging infrastructure, and changing social demographics. In this work, we create a framework to assess natural, built, and social stressors for water suppliers using Oregon as a case study that exemplifies the Western United States. First, a database of water system, geographic, and demographic data was developed to assess the current state of water supply vulnerability in Oregon. The compiled database was analyzed to develop a holistic view of the state’s water supply. Second, a network analysis was completed to reveal the interconnectedness of suppliers to assess vulnerability and redundancy. Finally, agglomerative hierarchical clustering analysis was performed to understand patterns of risk and define distinct water supplier typologies. Results indicate that there are diverse needs among water suppliers and risks across source areas. For example, some suppliers face a high risk of wildfires contaminating their source water, with 30-year burn probabilities of headwaters near 40%, while other suppliers serve growing populations whose needs may strain existing supplies. Many of the largest suppliers in the state, primarily located in the Portland metropolitan area, are connected through water transfers and a regional water consortium; however, the analysis elucidated several midsize suppliers that do not have as many resources or connections, presenting vulnerabilities. These suppliers may require further attention because they serve and supply a substantial population in more rural parts of the state. Lastly, the clustering analysis revealed four supplier typologies, confirming that many suppliers face similar stressors, although they are not necessarily geographically colocated. The results of our work indicate that future water supply resiliency and sustainability efforts could be further strengthened by collaborative efforts and knowledge sharing, particularly through non-neighboring partners, and by policies and programs developed to serve the unique needs of large urban, midsize regional, and small rural suppliers.