Abstract
The La Grande River watershed, located in the James Bay region (54°N, Quebec, Canada), is a major contributor to the production of hydroelectricity in the province. Peatlands cover up to 20% of the terrestrial environment in this region. Their hydrological behavior is not well understood. The present study is part of a multidisciplinary project which is aimed at analyzing the hydrological processes in these minerotrophic peatlands (fens) in order to provide effective monitoring tools to water managers. The objective of this study was to use VHR remote sensing data to understand the seasonal dynamics of the hydrology in fens. A series of 10 multispectral pan-sharpened GeoEye-1 images (with a spatial resolution of 40 cm) were acquired during the snow-free season (May to October) in 2009 and 2010, centered on two study sites in the Laforge sector (54°06'N; 72°30'W). These are two fens instrumented for continuous hydrometeorological monitoring (water level, discharge, precipitation, air temperature). An object-based classification procedure was set up and applied. It consisted of segmenting the imagery into objects using the multiresolution segmentation algorithm (MRIS) to delineate internal structures in the peatlands (aquatic, semi-aquatic, and terrestrial). Then, the objects were labeled using a fuzzy logic based algorithm. The overall classification accuracy of the 10 images was assessed to be 82%. The time series of the peatland mapping demonstrated the existence of important intra-seasonal spatial dynamics in the aquatic and semi-aquatic compartments. It was revealed that the dynamics amplitude depended on the morphological features of the fens. The observed spatial dynamics was also closely related to the evolution of the measured water levels.
Highlights
Hydroelectricity production in the province of Quebec is highly dependent on the hydrological conditions of the Mid-Northern region
Most of the errors appeared on the border of the site 1 fen, where they had no effect on the results of the hydrological study (Figure 5(a–d))
The aim of this work was to investigate the seasonal hydrological dynamics of minerotrophic peatlands with the help of multi-date GeoEye-1 very high spatial resolution images (VHR) imagery. This was done in order to answer the following questions: “Is it possible to delineate and classify the internal structures of peatlands with the help of VHR multispectral images?”; “Are there seasonal dynamics of aquatic and semi-aquatic structures in patterned fens and can this be quantified with these images?”; and “Can the observed dynamics be linked with the hydrological regime of fens?”
Summary
Hydroelectricity production in the province of Quebec is highly dependent on the hydrological conditions of the Mid-Northern region. The hydroelectric complex on the La Grande River covers a watershed of more than 177,000 km2[1]. The eight dams currently present on this river alone generate around 40% of the hydroelectricity in Quebec [2]. Since 1985, the water levels in these reservoirs have varied dramatically for reasons not currently understood [3]. One hypothesis involves variations in the storage of water by peatlands, which are strongly represented in the watershed. Peatlands, characterized by an accumulation of over 40 cm of peat [4], represent over 90% of Canadian wetlands [5]. They occupy about 20% of the terrestrial environment of the watershed of the
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