The Global Energy and Water Cycle Experiment (GEWEX) is a program initiated by the World Climate Research Program (WCRP) to observe, understand, and model the hydrological cycle and energy fluxes in the atmosphere, at land surface, and in the upper oceans. GEWEX is an integrated program of research, observations, scientific activities and the application of remote sensing technology to model regional hydrological processes and water resources. In conjunction with the GEWEX Continental-scale International Project (GCIP) in the Mississippi Basin, the Canadian contribution to GEWEX, the Mackenzie GEWEX Study (MAGS), conducted a series of large-scale hydrological studies within the Mackenzie River Basin. The central objective of MAGS is to develop a research methodology to model water and energy fluxes for a characteristic Canadian Arctic Basin (Pietroniro et al, 1996a).

The Liard River Valley is a large wetland-dominated sub-basin of the Mackenzie River Basin. This sub-basin has been selected as a research watershed representative of the wetland-dominated zone of discontinuous permafrost. The sub-basin can be further partitioned into six catchment areas that include: the Martin River, the Blackstone River, the Birch River, the Poplar River, the Jean Marie River, and the Scotty Creek catchment. The detailed analysis of flow pathways through wetland areas requires large-scale analysis of representative catchment regions. Consequently, project research initiates with the large-scale analysis of Scotty Creek, and then proceeds to the extrapolation of information for subsequent application to the analysis of the entire Lower Liard River Valley.

Research interests function to determine the unique combination of hydrological variables such as rainfall, soil moisture, snow cover, lake, ice, and glacier evaporation, and hydrologically significant terrain mapping to facilitate an increased understanding and prediction of energy flux (Quinton et al, 2000).

Glaciers helped to form the wetlands in Canada 9,000 to 12,000 years ago. Large wetlands formed when glaciers dammed rivers, scoured valleys, and reworked floodplains. Countless smaller wetlands were created as a result of large blocks of ice left behind by receding glaciers that formed pits and depressions in the land surface. Numerous depressions later filled with water due to poor drainage or intersection with the water table. Of recent interest in society is the relationship between the health of wetland regions and the human value obtained from them. Wetlands are considered one of the most productive ecosystems on earth. Such regions regulate water levels within watersheds, improve water quality, reduce flood and storm damages, provide important fish and wildlife habitat, as well as support hunting, fishing, and other recreational activities. Wetlands are important features in watershed management (Goldberg, 2000).

Regions inundated with water almost year round are termed wetlands. Ecosystems that develop on these lands subsequently are dominated by the presence of water excesses. Wetlands are found within flat vegetated areas, landscape depressions, as well as between water and dry land proximal to the edges of streams, rivers, lakes, and coastlines. The recurrent or prolonged presence of water at or near surface is the dominant factor determining the nature of soil development and the types of plant and animal communities living in the soil and on its surface (NWWG, 1988). Classification of wetlands environments can then be undertaken by the presence of unique vegetation termed hydrophytes that are adapted to life in soils that form under flooded or saturated conditions.

Wetlands occupy extensive regions of Canada. A significant proportion of these wetlands have been anthropogenically altered, some exploited for peat others drained for agricultural or forestry applications. The extent of wetlands in Canada is not known with any degree of accuracy. The distribution of wetlands in Canada is determined primarily by the climate and by the morphology of the land surface, alone or in combination. Climate functions to determine the volume of water a region receives through precipitation. Incoming energy plays an important role in the fate of the precipitated water lower incoming radiation rates generate a lower evapotransporation rate, consequently allowing water to pool on the surface.

Land morphology acts to influence the distribution of surplus water and the ultimate location of wetlands. Large, flat plains of fine-textured soils have the intrinsic property of poor internal and external drainage rates that result in surface water surplus. Within undulating surface topography wetlands may form in small, poorly drained depressions. In cool areas with low rainfall, wetlands usually develop only in depressions where water collects from adjacent slopes or from the upstream part of a catchment basin. Water may also be added to the system through groundwater discharge. In addition to climate and the surface configuration of the land, the physical and mineralogical characteristics of surface materials also influence wetland development. The texture of the surface material determines the porosity of the soil and therefore the proportion of water that can percolate into the soil (NWWG, 1988). The dependence for wetlands on climate and landforms is clearly illustrated by the distribution of wetlands in Canada (Figure 2). The greatest concentration of wetlands occurs in a belt across northern Ontario, central Manitoba and Saskatchewan, northern Alberta and the Mackenzie Valley (NWWG, 1988). The Mackenzie Valley is characterized by extreme cold in the winter months and cool temperatures throughout the summer months. In combination relatively low mean annual precipitation the region is hence favorable for wetland development.

The Mackenzie Basin is regulated by numerous diverse cold-region phenomena such as snow and ice processes, permafrost, Arctic clouds, and radiation interactions. These phenomena comprise essential components to a global climate system model. Collectively, the study of the Mackenzie and Mississippi Basins will provide a continental overview of hydrological processes. Micro-scale hydrological process knowledge may then be extrapolated and further applied to macro-scale hydrological models. The Mackenzie Basin is one of the great river basins of the world, ranking tenth largest by drainage area metric. Further, the Mackenzie River is the fourth largest river in North America and the largest North American river basin emptying into the Arctic Ocean. The basin has an area of 1.787 million kilometers square, equivalent to that of almost twenty percent of Canada's total landmass. The Mackenzie River flows through the North Western part of Canada into the Boufort Sea. Six major sub-basins comprise the Mackenzie system (Athabasca, Peace, Great Slave, Lower Liard, Great Bear, and Peel), three major lakes (Athabasca, Great Slave, and Great Bear), and three major river deltas (Peace-Athabasca Delta, Slave River Delta, and Mackenzie Delta). The hydrologic regime of the Mackenzie Basin is influenced by the major physiographic regions (Western Cordillera, Interior Plain, Precambrian Shield and Arctic Coastal Plain), permafrost which covers a significant portion of the basin, and vegetation which varies from Boreal forest to Arctic and alpine tundra.