Hydrologic Response to Forest Treatment Practices for Wildfire Mitigation in Sierra Nevada Watersheds
Abstract
Wildfires are an increasingly common occurrence in the Western United States. A disproportionate percentage of wildfires (61%) in the past 70 years have occurred within the most recent two decades. Mitigation measures or forest treatments such as plantation thinning, mastication and controlled burning, are being utilized to adapt to new fire regimes, mitigate fire intensity, and protect valuable resources. These treatments change forest structure which can alter the partitioning of water across the landscape. It is known that high intensity wildfires or treatments can lead to changes in runoff production, but few studies have looked at local hydrologic response when forest structure is not severely altered. However, minimal change to forest structure can have critical implications for regional and state water resources. This project aims to improve our understanding of the impacts of forest treatment on the water availability (water yield) in the western US. The Sagehen Watershed, located in the Sierra Nevada Mountains of California, offers a unique and ideal location to study this question, with different types of forest treatment occurring between 2014 and 2020. Continuous 15-min stream flow measurements at nine subcatchments within the Sagehen Watershed from 2012-2020 provide the spatial and temporal resolution needed to examine localized changes in streamflow following treatment. Specifically, we aim to answer (1) How do different forest treatment methods impact water yield in the Sagehen watershed; and (2) What are the key geophysical processes that determine how a watershed will respond to treatment methods? Preliminary results reveal that the Sagehen Watershed experienced higher stream flow between 2010 and 2020 relative to the long-term average, indicative of a change in hydrologic regime in the watershed. At the watershed scale, this change appears to be strongly correlated to changes in precipitation rather than forest treatment; however, subcatchment scale analysis reveals spatial variation in the relative roles of precipitation and treatment. Given the dramatic hydrologic and societal impacts of forest fires, the results of this study will inform water resource management decisions and natural resource protection measures to create climate resilient forests and water supplies.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2021
- Bibcode:
- 2021AGUFM.H52H..05B