Estimation de l'équivalent en eau du couvert nival au moyen d'images radar satellitaires

• Published in: Revue des sciences de l'eau
• Main Authors: J. L. Bisson, P. Vincent, Y. Gauthier, Monique Bernier, R. Gauthier, Jean-Pierre Fortin
• Format: Article in Journal/Newspaper
• Language: French
• Published: Université du Québec - INRS-Eau, Terre et Environnement (INRS-ETE) 2005
• Subjects: Sciences Humaines et Sociales; Social Sciences and Humanities; Équivalent en eau; Neige; Télédétection; Radar; RSO; Snow Water Equivalent; Snow; Remote Sensing; SAR; geo; envir; La Grande River; Subarctic; James Bay
• Online Access: http://www.erudit.org/fr/revues/rseau/1999-v12-n2-rseau3296/705358ar.pdf; https://www.erudit.org/en/journals/rseau/1999-v12-n2-rseau3296/705358ar.pdf; https://id.erudit.org/iderudit/705358ar; https://doi.org/10.7202/705358ar; https://core.ac.uk/display/59609997; https://www.erudit.org/fr/revues/rseau/1999-v12-n2-rseau3296/705358ar/; https://academic.microsoft.com/#/detail/2143704162

The goal of this study was to evaluate the potential of synthetic aperture radar (SAR) images for estimating the snow water equivalent (SWE) on the La Grande river watershed (James Bay area, Québec). This information is of major interest for Hydro-Québec, which exploits many hydroelectric complexes throughout this subarctic region. The La Grande watershed is composed of moderately dense to opened black spruce forests, opened areas, burned areas and peat bogs. Over two years (1994-1995), six field campaigns were carried out on a study site located between the LG4 and Laforge1 reservoir, in the center of the La Grande river watershed. The field measurements were of two types: 20 snow lines (depth, snow water equivalent (SWE), density) and 8 snow profiles (depth, density, grain size, temperature, dielectric constant). With these data, the thermal resistance of the snowpack was calculated for every test-site, using the depth, density and thermal conductivity of each layer. Concurrently, more than 10 SAR images (European Satellite ERS-1) of the study site were acquired, calibrated and georeferenced. The backscattering coefficients of all winter images were extracted. Using a reference image (snow-free), backscattering ratios were calculated. They are the difference between a winter image and a snow-free image. This process is used to reduce the impact of vegetation and topography. Then, the relationship between the backscattering ratios and the snowpack thermal resistance of february and march 1994 are established, as the first part of an algorithm developed to estimate the snow water equivalent. The second part of the algorithm infers the snowpack water equivalent from its thermal resistance and density, based on the physical relationship established with field data. This approach is based on studies conducted by INRS-Eau in a southern Quebec agricultural area (BERNIER and FORTIN (1998)). The hypothesis are based on the following: - The snowpack characteristics influence the underlying soil temperature;- The ...