CONNECTED WATERS OF BOREAL WETLANDS: ROLE OF INTEGRATED MODELLING IN GAINING INSIGHTS INTO COMPLEX SHALLOW FLOW SYSTEMS

Organic wetlands play an important role in the hydrology of the Boreal regions. Increasing oil and gas, industrial and infrastructural activities in northern latitudes are forcing detailed studies of organic wetlands driven by the need to understand regional, intermediate and local flow systems. Physical and geological settings, peat thickness and the history of wetland formation determine the overland and subsurface flow regime.

Although the geological setting underlying the peat layers varies spatially, thick low permeability drift deposits are common in central and northern Alberta. These types of geological settings and frozen conditions during spring melt promote shallow flow through surficial peat layers and as overland flow. This implies that deeper flow may not have a greater role in the local flow system, yet the physical settings may lead to flow through the underlying drift material.

Because wetlands alternate seasonally between overland and subsurface flow systems, groundwater modelling alone is not enough to provide comprehensive understanding of wetland flow characteristics. Further, presence of shallow organic lakes necessitates use of integrated surface water and groundwater modelling.

This paper presents results of an integrated modelling at a fen complex in northern Alberta. The modelling study was driven by the need to understand flow and transport processes at a site consisting of a narrow fen complex characterized by presence of two shallow organic lakes. The modelling was aimed at understanding the local flow regime, quantifying the flow through the narrow fen complex and to understand the interaction between the lakes through the underlying drift material. The study throws light on the seasonal behaviour of the wetland system. The modelling results suggest that the local flow behaviour is strongly influenced by the physical setting. Therefore, detailed investigations of peat and organic lake properties including characterization of Gyttja layer are crucial in improving understanding of the flow system. The study further highlights the importance of integrated modelling in improving conceptual models of such complex systems.