The effects of cumulative forest disturbance on streamflow in a large watershed in the central interior of British Columbia, Canada

Abstract

Abstract. The Baker Creek watershed (1570 km 2 ), situated in the central interior of British Columbia, Canada, has been severely disturbed by both logging and natural disturbance, particularly by a recent large-scale mountain pine beetle (MPB) infestation (up to 2009, 70.2 % of the watershed area had been attacked by MPB) and subsequent salvage logging. The concept of equivalent clear-cut area (ECA) was used to indicate the magnitude of forest disturbance, with consideration of hydrological recovery following various types of disturbance (wildfire, logging and MPB infestation), cumulated over space and time in the watershed. The cumulative ECA peaked at 62.2 % in 2009. A combined approach of statistical analysis (i.e. time series analysis) and graphic method (modified double mass curve) was employed to evaluate the impacts of forest disturbance on hydrology. Our results showed that severe forest disturbance significantly increased annual mean flow. The average increment in annual mean flow caused by forest disturbance was 48.4 mm yr −1 , while the average decrease in annual mean flow caused by climatic variability during the same disturbance period was 35.5 mm yr −1 . The opposite changes in directions and magnitudes clearly suggest an offsetting effect between forest disturbance and climatic variability, with the absolute influential strength of forest disturbance (57.7 %) overriding that from climate variability (42.3 %). Forest disturbance also produced significant positive effects on low flow and dry season (fall and winter) mean flow. Implications of our findings for future forest and water resources management are discussed in the context of long-term watershed sustainability.

Global pattern for the effect of climate and land cover on water yield

“…The large role of m in hydrological responses is supported by published studies [26][27][28] , which shows that land cover change can significantly alter m values and lead to a larger role in hydrological responses than climate (P/PET).…”

Runoff Response to Climate Warming and Forest Disturbance in a Mid-Mountain Basin

“…The spatial scale of the assessment is here one of the key factors affecting interpretation and understanding of the underlying processes. A number of studies have been done to analyze the impact of forest harvesting and clear-cutting on annual runoff, and most of them agreed that the runoff will be affected less by increasing the size of the basin [9,25]. At different scales of observation, individual driving processes and factors may be more or less important.…”

“…Forest disturbance, as one of the causes driving severe land cover change, has major impacts on interception, evapotranspiration, surface soil hydraulic conductivity, and soil storage, which may lead to changes in the water yield [15,16], the runoff formation process [17,18], snow hydrology [19,20], floods [9,21], and the low-flow regime [22,23]. The effects of different forest disturbances caused or triggered by wildfire, insect infestation, windstorm, logging, pollution, urbanization, agricultural activities, and management interventions on the stream flow have been widely studied at multiple temporal and spatial scales [24][25][26][27][28]. Appropriate environmental policy regarding basin management requires an integrated understanding of the hydrological responses to both climatic and changes in forest land cover, especially in montane areas, which are highly vulnerable to these changes [25,29].…”

“…The effects of different forest disturbances caused or triggered by wildfire, insect infestation, windstorm, logging, pollution, urbanization, agricultural activities, and management interventions on the stream flow have been widely studied at multiple temporal and spatial scales [24][25][26][27][28]. Appropriate environmental policy regarding basin management requires an integrated understanding of the hydrological responses to both climatic and changes in forest land cover, especially in montane areas, which are highly vulnerable to these changes [25,29].…”

Assessing the Impact of Forest Change and Climate Variability on Dry Season Runoff by an Improved Single Watershed Approach: A Comparative Study in Two Large Watersheds, China

“…Despite its successful application in both China and Canada [26][27][28][29][30], this approach can only be used in watersheds with limited human activities since it cannot differentiate the hydrological impact of other confounding factors including urbanization and agricultural activities from that of forest change. As a matter of fact, few forested watersheds worldwide are exempt from human impact.…”