Associations between watershed characteristics, runoff, and stream water quality: hypothesis development for watershed disturbance experiments and modelling in the Forest Watershed and Riparian Disturbance (FORWARD) project

The FORWARD project, based on the Boreal Plain of Alberta, was initiated to develop models to predict the influence of watershed disturbance on runoff and stream water quality. To generate hypotheses relating to watershed controls on streams in the presence and absence of disturbance, we quantified relationships between stream variables and soil distribution in nine undisturbed small (M = 5.4 km²) watersheds for two relatively dry and snowmelt-dominated seasons (May through October 2002 and 2003). We also considered data from one harvested and two burned watersheds. Among soil types, only peatland cover had an association with runoff and water quality. Runoff and ammonium exports were positively related to peatland cover in both years (r² = 0.50 to 0.90; P < 0.05). In the first year, additional relationships to peatland cover existed for particulate phosphorus and suspended sediment exports (r² = 0.64 and 0.65, respectively), whereas in the second year they existed for dissolved phosphorus and dissolved organic carbon exports (r² = 0.67 and 0.78, respectively). Hypotheses generated relate to the role of peatlands as sources for water moving toward stream channels, water exchange between streams and riparian groundwater, and the influence of disturbance and precipitation patterns on runoff generation. Key words: watershed disturbance, boreal forest, peatland, stream, suspended sediments, nutrients, runoff, forest harvest, wildfire.