Forest Investment Account (FIA) - Forest Science Program
FIA Project M075036

    Using GIS and Time Series Analysis to Evaluate Impacts of Large-Scale Forest Logging on Hydrology in the BC Interior
Project lead: Wei, Adam
Author: Wei, Adam
Imprint: Kelowna, BC : University of British Columbia Okanagan, 2007
Subject: Forest Investment Account (FIA), Dendroctonus Ponderosae, British Columbia
Series: Forest Investment Account (FIA) - Forest Science Program
In 1975, a widespread spruce bark beetle infestation in the Bowron watershed (watershed size: 3590 km2) led to a large-scale salvage logging operation lasting approximately 10 years. This harvest of approximately 900 km2 represents nearly 25% of the watershed and remains as one of the largest clear-cut areas in province. The long flow records (from 1954 to present) from the hydrometric station located at the bottom of the watershed, together with the historic occurrence of massive salvage logging provides us with an unique, rare research opportunity to evaluate the impacts of large-scale forest disturbance on hydrology. A neighboring watershed, the Willow watershed (size: 3110 km2), with similar size and long-term flow records also experienced large-scale forest harvesting. Please refer to the attached map (appendix) for logging history in two watersheds. The impacts of timber harvesting or forest disturbance on hydrology have long been the subject of considerable study and debate (Andreassian 2004; Post and Jones 2001; Wei et al. 2005). Such data is important for supporting implementation of results-based regulations, designing sustainable forest management practices and protecting watershed functions. However, much of the previous research into hydrologic impacts in BC has focused on small watersheds (<100km2), and the results from these small watershed studies are difficult to apply to large-scale watersheds. Lack of information on ecological impacts of large-scale forest disturbance greatly constrains our ability to plan forest management strategies at the watershed-scale or landscape-level. This clearly highlights a significant need to conduct studies to examine the impacts of large-scale forest disturbance on hydrology. This proposed research will be complementary to a few current and proposed projects in BC (see the Linkage section for more details). Previous studies have used the paired watershed or replication approaches for evaluation of forest disturbance impacts, particularly for small-scale watersheds. Where such a control or replication is impossible for large-scale watersheds (>1000 km2) due to their availability or cost constraints, time series analysis is a useful tool for analyzing unreplicated and serially-correlated hydrological data. Time series analysis has been widely used in forecasting and environmental assessment (Box and Jenkins 1976; Box et al. 1994; Chatfield 1989). Jassby and Powell (1990) provide a useful review on methods of detecting changes in ecological time series, and they recommended a cross-correlation technique for inference of causation between two time series and intervention analysis for evaluation of impacts of unusual events. Both watersheds have been gauged since early 1950ís, and annual harvesting data has also been documented by the BC Ministry of Forests in the same timeframe. Based on data availability and our literature review, we propose to use GIS and time series analysis to evaluate impacts of large-scale salvage logging on hydrology in the Bowron and Willow watersheds in the BC interior. GIS is a powerful tool for spatial analysis and it will be used in this study to delineate logging history in the watersheds and the severity over time so that a data series of forest changes (i.e. equivalent clear-cutting area or ECA) due to salvage logging or harvesting can be established for time series analysis. Combination of GIS and times series analysis represents an innovative approach to study large-scale disturbances and associated hydrological effects. Adam Wei successfully used a similar approach to conduct a preliminary analysis for the Borwon watershed based on limited data in 1997. With additional 8-years flow record and inclusion of the Willow watershed, this proposed study will provide sound results on impacts of large-scale salvage logging on hydrology in the BC interior. Although time series analysis will be done separately for the Bowron and Willow watersheds, inclusion of the Willow watershed will be useful for comparing the possible differences in hydrological impacts between salvage logging and normal timber harvesting. Our recently established advanced GIS and remote sensing lab at UBC Okanagan will ensure successful implementation of the proposed research.
Contact: Wei, Adam, (250) 807-8750,


Executive summary (23Kb)

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Updated August 16, 2010 

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