Impacts of Forest Disturbance on Hydrology in Large Watersheds

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The impact of forest disturbance on hydrology has long been an important research topic, but the majority of this research has been conducted on small watersheds (<100km2) with rare examination of large ones (>1000km2). It is commonly accepted that the results from small watersheds are difficult to extrapolate to large watersheds. Large watershed studies are constrained by the difficulty of conducting paired-watershed experiments, and by insufficient data, landscape complexity and lack of accepted methodologies. However, growing demand for information at large spatial scales to support forest and watershed management highlights a critical need for the research of large watersheds. With the support from my NSERC Discovery Grants (2005-2012; 2013/2014), we have successfully developed a research method for separating relative contributions of forest disturbance and climate variability to hydrology in large watersheds, and the applications of the method have been published on the high-impact journals (e.g., Water Resources Research, Journal of Hydrology). The objectives of this new research (2014-2019) include: (1) applying our well-established methodology in 10 more large watersheds from the interior of British Columbia to assess the cumulative effect of forest disturbance (mainly wildfire, mountain pine beetle infestation, timber harvesting or commonly their combinations) on hydrology; (2) using the VIC model to predict the cumulative effects of future forest disturbance and climate change scenarios on hydrology in three of the selected watersheds; and 3) using an integrated meta-data analysis to develop emerging watershed properties or indices which can effectively explain large variations on hydrological responses to watershed disturbance in large watersheds. Those selected watershed properties or indices will help establish a conceptual framework on watershed sensitivity assessment, which can be further tested in boreal watersheds or elsewhere. My longer-term goal (beyond this proposal) is to establish a research program entitled “Forest Disturbance, Climate and Hydrology in Large Watersheds” to advance watershed ecosystem science. Availability of numerous large watersheds (35-40) with excellent data in the British Columbia interior provides an exceptional opportunity to achieve my goal. The proposed research will provide important and timely information for BC to manage forest disturbance to protect aquatic functions. It will allow development of forest disturbance thresholds as well as identification of possible emerging watershed properties or indices for explaining large variations on hydrological responses to forest disturbance among different watersheds. Finally, this project will train 2 HQPs and 4-5 undergraduate students who will be specialized in ecohydrology and water science/management.