Streamflow response in Boreal Plains catchments depends on hydrological connectivity between forested uplands, lakes, and peatlands, and their hydrogeomorphic setting. Expected future drying of the Boreal Plains ecozone is expected to reduce hydrological connectivity of landscape units. To better understand run-off generation during dry periods, we determined whether peatland and groundwater connectivity can dampen expected future water deficits in forests and lakes. We studied Pine Fen Creek catchment in the Boreal Plains ecozone of central Saskatchewan, Canada, which has a large, valley-bottom, terminally positioned peatland, two lakes, and forested uplands. A shorter intensive study permitted a more detailed partitioning of water inputs and outputs within the catchment during the low flow period, and an assessment of a 10-year data set provided insight into the function of the peatland over a range of climate conditions. Using a water balance approach, we learned that two key processes regulate flow of Pine Fen Creek. The cumulative impact of landscape unit hydrological connectivity and the peatland's hydrological functional state were needed to understand catchment response. There was evidence of a run-off threshold which, when crossed, changed the peatland's hydrological function from transmission to run-off generation. Results also suggest the peatland should behave more often as a transmitter of groundwater than as a generator of run-off under a drier climate future, owing to a reduced water supply.

This study re‐evaluated data from the historical Tri‐Creeks Experimental Watershed (1967–1988) in Alberta, Canada to address the initial question of forest harvest effects on streamflow and investigate the potential influence of teleconnections, summer‐dominated precipitation, and watershed storage on runoff generation. Tri‐Creeks has deep (up to 21 m) glacial deposits underlain by folded and faulted sedimentary bedrock with considerable potential for subsurface water storage. Timing of the conifer forest harvest experiment in two sub‐watersheds (>50% harvested) and one reference occurred near the 1976–77 Pacific Decadal Oscillation (PDO) phase change that led to less snowfall, but little difference in annual precipitation or runoff between phases after harvest. Established statistical and hydrological modelling methods that used regression techniques of observed and simulated streamflow to separately analyse sub‐watersheds did not detect change in average daily or annual runoff due to harvest. The interannual hydroclimatic variability influenced by the climate shift, attenuation of summer precipitation by the drier antecedent conditions in the warm period following harvest, and large potential for subsurface water storage contributed to shifts in runoff and uncertain detection of streamflow response. However, a hydrological modelling approach using calibrated parameters separately in the pre‐ and post‐harvest periods indicate significant change in rainfall‐generated peak runoff events and summer runoff following harvest, which was not detected in the reference watershed. Model calibration required less soil storage capacity in the treated watersheds in the post‐harvest period compared to the reference likely due to reduced transpiration that increased the likelihood of storm runoff during larger summer rainfall events. Within the context of streamflow responses to harvest in conifer dominated forest landscapes with seasonal snow cover, this study illustrates how complexity of climate variability and interaction with watershed storage and continental summer‐dominated precipitation may confound and mask the interpretation of harvest effects in paired‐watershed studies.

Tri-Creeks Experimental Watershed was initiated to compare the effects of logging and riparian buffers in three subbasins (Wampus, Deerlick, and Eunice Creeks) and to evaluate the effectiveness of timber harvesting ground rules in protecting fisheries and water resources. The watershed study was terminated in 1985 shortly after the harvest. In 2015, the University of Alberta re-established groundwater monitoring, hydrometric, and meteorological stations in Tri-Creeks Experimental watershed. Future research will utilize the 20-year historic data set and current data to study the the effect of forest cover change on the streamflow regime and fish populations. The objective of this paper is to summarize the novel results and available data from 1965-1987 for the Tri-Creeks Experimental Watershed. RÉSUMÉ Results Timber harvestFifty percent of merchantable timber harvested (39% of Wampus and 40% of Deerlick) resulted in a 7% and 22% increase in seasonal water yield for Wampus Creek and Deerlick Creek, respectively. However, these quantifiable changes could not be attributed to the harvest because the before and after treatment results were not statistically significant (Andres et al. 1987).Other factors that likely contributed to the lack of significant change were:• Short duration of the post-harvest monitoring (only 2-3 years).

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