Hydrologic dynamics following wildfires in California and Hydrological and Chemical Resilience to Compounding Wildfires

Talk 1 Abstract

In recent years, wildfires in the western United States have occurred with increasing frequency and scale due to prolonged periods of droughts and increasing temperatures. Wildfires occurring in the headwaters or foothills of the Sierra Nevada Mountains of California can have serious implications for water supply, given that up to 70% of state water resources originate from these regions. Despite the significant impact wildfires have in shaping the landscape, their role in altering hydrologic states and fluxes are still highly uncertain due to the strong non-linearities known to exist in the integrated (above- and below- ground) water cycle. Using high performance computing, we simulate a representative watershed that spans the Sierra Nevada-Central Valley interface with and without-landscape changes resulting from wildfires. Model result allow us to identify the regions most hydrologically sensitive to post-wildfire conditions, as well as the processes that are most impacted by landscape changes following a wildfire. For example, increases in snowpack following a wildfire lead to increased summer runoff and groundwater storage. Furthermore, our simulations reveal how sometimes counterintuitive effects may emerge following a wildfire, such as increases in evapotranspiration rates in areas where subsurface flow pathways are altered due to burn scars.

Erica Woodburn
Research Scientist
Energy Geosciences Division
Lawrence Berkeley National Laboratory

Erica Woodburn, Ph.D.
Research Scientist
Energy Geosciences Division
Lawrence Berkeley National Laboratory

Biography

Erica Siirila-Woodburn is a research scientist at Lawrence Berkeley National Laboratory with a focus on computational hydrology. She and her group study the movement and partitioning of water in natural and managed environments ranging from hillslope to watershed scales, with recent topics including climate change and extremes, groundwater storage dynamics, and quantitative risk assessment. Erica received her Ph.D. in hydrology from the Colorado School of Mines in 2013 and was a postdoc at the Polytechnic University of Barcelona before joining Berkeley Lab in 2015.

  

Talk 2 Abstract

Wildfires are a natural yet changing component of many landscapes around the world. From 2017-2020, a series of multiple fires devastated many forested, agricultural, and urban areas within Sonoma, Mendocino and Napa counties, California, U.S.A, and across the Russian River Watershed. The compounding burn areas provide significant sources for ash-leachate runoff flowing to the Russian River, and nearby tributaries during subsequent rainfall events. In addition, leachate infiltrate to local groundwater basins supports groundwater discharge to the Russian River during the dry season. The central objective of this work is motivated by four research questions to enhance understanding of resilience at the watershed scale: 1) How do compounding fire events impact hydrological, chemical, and microbial conditions of the river corridor network and watershed?, 2) How do post-fire storm events impact hydrological, chemical, and microbial connectivity across the watershed including the tributaries, and main stem?, 3) What hydrobiogeochemical metrics are critical indicators of the watershed resilience and potential thresholds?, and 4) Can such data be used to identify critical resilience tipping points as identified within these observational networks? We introduce point-scale metrics within the river corridor of the Russian River Watershed, a multi-scale watershed network impacted by wildfire. By analyzing these observational metrics as critical signals of entire landscape-scale resilience, this work will inform how resilience is identified, and mechanisms that potentially impart resilience within a landscape.

Michelle Newcomer
Research Scientist
Climate & Ecosystem Sciences
Lawrence Berkeley National Lab

Michelle Newcomer, Ph.D.
Research Scientist
Climate & Ecosystem Sciences
Lawrence Berkeley National Lab

Biography

Dr. Michelle Newcomer¬†is a Research Scientist in the Climate & Ecosystem Sciences Division at Lawrence Berkeley National Laboratory. Dr. Newcomer’s research focuses on topics in hydrology, groundwater, climate, biogeochemistry, and her research is leading the way in emerging interdisciplinary topics such as how climate impacts surface-water groundwater interactions, biogeochemical cycling, and algal blooms. In her most recent work, Michelle is leading a large-scale long-term watershed approach to understanding watershed changes after fires in a west coast US watershed impacted by multiple and compounding fires each year. Michelle is also leading the river corridor component of the Watershed Function Scientific Focus Area, a large DOE project at the scientific frontier of understanding how watersheds function to deliver water and nutrients downstream.