After the fire: Informing water systems management in burned landscapes

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Wildfires create hazards for lives and property through combustion and high temperatures, as well as their impacts to catchment source water. This project focuses on these water-related vulnerabilities, which include far-reaching effects on flood risks (Ebel et al., 2012), on aquatic habitats, and on water treatment costs (Hohner et al., 2019; Pitlick and Van Steeter, 1998).

High sediment and ash loads transported from postfire landscapes require costly water treatment procedures (Raseman et al., 2018) or use of alternate water sources. Furthermore, wildfire-driven dissolved organic matter (DOM) can react with chlorine disinfectants to produce carcinogenic disinfection byproducts. After a fire, water suppliers face a critical decision on whether to divert this low-quality water or let it bypass their intakes, risking their financial bottom line by not delivering anticipated water quantities to their municipal and agricultural customers. The high treatment costs of sediment and ash-laden waters may be tradeoffs for water shortage. In a normal year, these types of water providers are focused on the total volume of water, but recent fires have meant that most years have not been “normal,” requiring water quality considerations as well as quantity. Water providers are facing short- and medium-term decisions about a fire response plan, including installation of sedimentation banks, and seeking longer-term information on which ‘types’ of watersheds will thrive in a warmer, more fire-prone future—specifically, which types of vegetation, topography, soils, etc. will constitute a watershed that will experience less severe post-fire impacts.

In Phase 1 of this project (2022-2023), we aim to quantify postfire hydrologic and water quality risks in the form of spatial “layers” of expected responses from varying wildfire severities, rainfall intensities and catchment properties. A new data-driven statistical model and a version of the process-based Variable Infiltration Capacity (VIC) model (Stewart et al., 2017) will be validated with local streamflow and water chemistry data. Data from the High Park Fire in 2012 and the Cameron Peak Fire in 2020 near Fort Collins, CO will also be used. Model parameters will be informed by an experimental dataset generated by Livneh’s laboratory-scale wildfire and rainfall simulator over the past 2.5 years (Brucker and Livneh, 2018). To address both Northern Water and Denver Water decision points, we seek to provide guidance on how watersheds may respond to fire, i.e., which watersheds are more likely to thrive in the future, versus which watersheds are likely to produce lower-quality postfire water that will challenge operations. 

In Phase 2 of this project (2024-2026), we will engage with Denver Water, Northern Water, and small, underserved utilities with water systems that are vulnerable to wildfire. Engagement will include improving understanding of both resilience status and adaptive capacity. This understanding will help us to co-develop key questions, tools, or products that utilities can use to increase water system resilience. We will explore existing toolkits and wildfire-water system activities in other regions, and produced by state and federal agencies like the US Forest Service, to inform activities in Phase 2, and to promote cross-region learning and build on existing knowledge.

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