Hydrological Functioning of a Constructed Watershed

English Abstract:

Reclamation in the oil sands areas requires the reconstruction of entire landforms and drainage systems. Much reclamation research has focused on assessing the performance of individual hillslopes; however, there is a need for an integrated, catchment-scale approach to fully develop an understanding of the hydrological functioning of constructed watersheds. This research aims to couple the controls on water distribution, storage and release within individual landforms (reclaimed slopes, tailings sand upland aquifer and fen peatland) to their hydrologic role (i.e., storage or conveyor) within the context of the larger scale landscape in a constructed system.

The oldest slope (reclaimed in 2007) exhibited a surface infiltration rate three times larger than slopes reclaimed more recently (2012). Consequently, soil water storage was reduced on the 2012 slopes and infiltration-excess surface runoff generation conveyed water rapidly downslope during intense precipitation events. In the fen peatland, high water table levels were sustained throughout the summers of 2013 and 2014, with persistent ponded water in localized depressions in the surface of the placed peat. Large upward hydraulic gradients measured in the fen suggest strong connectivity with the tailings sand upland aquifer; however very low surface infiltration rates on the capping upland reclamation soil constrained recharge to the sand aquifer, which remains below designed water contents in much of the upland.