CONSPECTUS: Wildfires are a natural part of most forest ecosystems, but due to changing climatic and environmental conditions, they have become larger, more severe, and potentially more damaging. Forested watersheds vulnerable to wildfire serve as drinking water supplies for many urban and rural communities. The highly variable nature of wildfire behavior combined with spatially complex patterns in vegetation, landscape, and hydrologic factors create uncertainty surrounding the postfire effects on water supplies. Wildfires often cause dramatic changes in forest vegetation structure and soil conditions, and alter the watershed processes that control streamflow, soil erosion, nutrient export, and downstream water chemistry. The authors' work centers on field and laboratory studies to advance knowledge of postfire changes in soil and water chemical composition that influence drinking water treatment. High intensity postfire rainstorms typically increase runoff that erodes ash and soil from burned landscapes and dramatically elevates turbidity, nutrient, and dissolved organic carbon (DOC) levels in surface waters, which can cause short-term challenges for water providers. There is also growing evidence that water quality impacts can persist after high severity fires due to slow vegetative recovery, and nitrogen and DOC have remained elevated for 15 years following high severity fire. Low-moderate temperatures during wildfire may also influence water quality. Research by the authors showed that the solubility of organic matter, and C and N released from soils increased following soil heating at temperatures ≤ 350 °C. Further, the water extracted organic matter from soils heated at 225−350 °C included higher proportions of condensed aromatic structures, such as black carbon and black nitrogen. Short-term postfire water quality degradation following high intensity rainstorms can force water treatment plants to shut down or can significantly challenge treatment process performance. Extreme turbidity and high DOC in poststorm water, coupled with compositional organic matter changes, reduced the coagulation efficiency of postfire water supplies. Field and lab-based studies documented the formation of small, aromatic soluble compounds during wildfire that contribute to inefficient DOC removal from postfire stormwater. Due to increased postfire DOC concentrations, and poor treatability of poststorm runoff, toxic disinfection continued...

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To characterize the effects of thermal-alteration on water extractable organic matter (WEOM), soil samples were heated in a laboratory at 225, 350, and 500 °C. Next, heated and unheated soils were leached, filtered, and analyzed for dissolved organic carbon (DOC) concentration, optical properties, molecular size distribution, molecular composition, and disinfection byproduct (DBP) formation following the addition of chlorine. The soils heated to 225 °C leached the greatest DOC and had the highest C- and N-DBP precursor reactivity per unit carbon compared to the unheated material or soils heated to 350 or 500 °C. The molecular weight of the soluble compounds decreased with increasing heating temperature. Compared to the unheated soil leachates, all DBP yields were higher for the leachates of soils heated to 225 °C. However, only haloacetonitrile yields (μg/mg) were higher for leachates of the soils heated to 350 °C, whereas trihalomethane, haloacetic acid and chloropicrin yields were lower compared to unheated soil leachates. Soluble N-containing compounds comprised a high number of molecular formulas for leachates of heated soils, which may explain the higher yield of haloacetonitriles for heated soil leachates. Overall, heating soils altered the quantity, quality, and reactivity of the WEOM pool. These results may be useful for inferring how thermal alteration of soil by wildfire can affect water quality.

His research evaluates the relation between environmental processes and water infrastructure, both from the perspective of how watershed processes control source water quality and how wastewater effluent affects downstream ecological function. Writer has studied various types of watershed disturbances (e.g. floods, drought, wastewater) to evaluate their corresponding effects on water resources. Writer's research links engineering, chemistry, hydrology, and ecology to better understand the complexities of contaminant transport and its effect on aquatic ecosystems and water resources. He received his bachelor's degree from Brown University in Providence, R.I., and his master's and doctorate degrees from the University of Colorado at Boulder

2020 is the year of wildfire records. California experienced its three largest fires early in its fire season. The Pantanal, the largest wetland on the planet, burned over 20% of its surface. More than 18 million hectares of forest and bushland burned during the 2019-2020 fire season in Australia, killing 33 people, destroying nearly 2500 homes, and endangering many endemic species. The direct cost of damages is being counted in dozens of billion dollars, but the indirect costs on water-related ecosystem services and benefits could be equally expensive, with impacts lasting for decades. In Australia, the

Optical measurements reveal the presence of pyrogenic organic matter in laboratory heated soil leachates, indicating their potential for application in field measurements.

What is the present research focus of your group?My research group evaluates the effects of extreme events and watershed disturbances on the resilience of drinking water systems. We study how events such as wildfire, floods, and droughts affect source water quality and treatment process performance, and how utilities can best adapt to address these disruptions in water quality. What motivated the research behind your recent article in AWWA Water Science-that is, what problems are you trying to solve?Our research was motivated by the needs of water utilities across North America, but especially utilities in the West that have experienced wildfires or are concerned about the risk of future wildfires to their water treatment system. The rise in wildfire 24 JOURNAL AWWA T h e o r y a n d P r a c t i c e o f S a f e , S u s t a i n a b l e W a t e r www.awwawaterscience.com Amanda (Mandi) collects water samples from the Naches River in central Washington during a day trip with her research group. The Naches River supplies drinking water to the City of Yakima; upstream drainage areas were burned in 2017 by the Norse Peak fire in the Cascade Mountains.

Re-suspension of post-fire sediment deposits challenge conventional water treatment processes during runoff events, impacting DBP formation. Treatment thresholds for a range of unit processes are established.