Dendrochronological analysis of past hydro-climatic variations in La Grande river complex in Northern Quebec
Résumé
In order to retrace the evolution of the hydrological regime parameters with time, we have reconstructed the main hydroclimatological variables used in forecast models. The study was conducted in the region of the James Bay hydroelectric complex of La Grande. Trees occupying sites sensitive to water availability variations (xeric, mesic and hydric sites) and those sensitive to thermal conditions (depending on exposition) give the opportunity to reconstruct climate variability between years. A calibration period with instrumental data is essential and it is also important to verify the models relating rings to climate with independent data. More than one hundred treering series covering more than 180 years, tens series of more than 250 years and one series covering one thousand years have been reconstructed. These tree-ring series cover an area of 320 000 km(2) (800 km in longitude x 400 km in latitude). Summer temperatures, snow precipitation and seasonal water supply were reconstructed over the past 200 years by means of various tree-ring proxies: ring width, density (9 derived variables) and ratios of stable isotopes of oxygen and carbon.