Technical Bulletin No. 0969: Effects of Forest Management on Water Resources in Canada: A Research Review

Although forestry practices commonly occur at the stand level, watersheds are used as the study unit for hydrological and water quality issues. Watersheds are natural or artificial drainages on which all precipitation and emanating spring discharges collect and flow to a common outlet. To establish a cause-and-effect relationship of ecosystem response to disturbance, it is essential to determine watershed level impact by removing biases that could occur at smaller scales. However, since the hydrologic cycle is driven by numerous processes that occur at smaller scales (e.g., evapotranspiration and snow melt), stand-level research is also vital in understanding responses at the watershed scale.

More than 25 research watersheds in Canada have been used to examine the hydrologic and water quality impacts of forestry practices. Research has shown that the effects of forest management on hydrology and water quality are highly variable in both magnitude and duration. Factors such as topography, sub-surface geology, forest type, watershed composition and extent of harvest all play a part and are difficult to separate.

Although a common goal in hydrological research is to transfer information gained at one scale of study to larger or smaller scales, or to transfer knowledge from one region to another, the field of forest watershed research is rife with scaling issues and uncertainty in transferability. The watershed research community is moving toward embracing these challenges. For example, several watershed research projects in Canada are incorporating information about stand-level processes in simulation models.

Watershed studies should be conducted in the ecozones in which the results will be applied for forest management.