Comparison of streamflow between pre and post timber harvesting in Catamaran Brook (Canada)

The forest industry plays a major role in the economy of eastern Canada. The recreational fishery also represents an important source of revenue for this area. Therefore, there is concern over the potential economic effects and ecological impacts from logging operations on aquatic habitats. The present study deals with the comparison of streamflow between pre and post timber harvesting at Catamaran Brook (New Brunswick, Canada) to identify any potential changes to the hydrological regime. Studies were carried out on two sub-basins of Catamaran Brook, namely the Middle Reach (mid-basin) and the Upper Tributary 1. The harvested area at the Middle Reach represented 2.3% of this sub-basin while 23.4% of Upper Tributary 1 was harvested. It was noted that during both the calibration and timber harvesting phases, meteorological conditions (e.g. precipitation, runoff) contributed to relatively high natural variability. When studying changes on an annual and seasonal basis for the basin cut at 2.3% (i.e. Middle Reach) and using a control basin for comparison, no changes were detected to the annual water yield, seasonal runoff and streamflow timing between the calibration and timber harvesting phases. On a summer rainfall event basis, no changes were detected at the Middle Reach and the Upper Tributary 1 when studying relations between precipitation and stormflow (obtained through hydrograph separation). Alternatively, changes were detected in relations between peak flows and precipitation (p < 0.05) at the Upper Tributary 1 when comparing the calibration and timber harvesting phases. Peak flows showed higher values following timber harvesting. No significant changes were observed between peak flows and precipitation at the Middle Reach. When comparative studies were carried out on peak flow and stormflow between sub-basins (using the Middle Reach as control for treatments vs. the most affected site, i.e. Upper Tributary 1), significant changes were detected in peak flow (p < 0.05) between the calibration and timber harvesting phases at the Upper Tributary 1 only. Increased peak flows were observed at the Upper Tributary 1 compared to the Middle Reach following timber harvesting. It was concluded that for timber harvesting at Catamaran Brook, changes could only be detected on a summer storm event basis for the most affected site (Upper Tributary 1) and for peak flow only. (C) 2002 Elsevier Science B.V. All rights reserved.