| Summary: | International audience Climate change plays a major role in determining future water availability and quality in several parts of the world. With the potential for hydroelectric development on the Churchill River, Labrador, it is important to understand the influence of climatic conditions on river discharge to foresee potential climate change effects on future productivity. Persistent drought events recorded between 1940 to 1960 and 1985 to 2000 underline the significant risk that changing climate may represent for energy supply, infrastructure security, and Canadian economy. Typically, predictive climatic models use historical temperature and precipitation records. In the study region (eastern Canada), climatic data cover less than seventy years and long reconstructions from natural archives are inexistent, which means it is unrealistic to simulate hydro-climatic variabilities and estimate future drought risks. In the boreal climate, tree-ring δ13C and δ18O series can: (1) be directly linked to climatic conditions, individually or in combination, and (2) reflect river discharge, a regional integration of overall climatic conditions. This study aims at improving the knowledge of long-term hydrologic variability in eastern Canada by reconstructing regional discharge from tree-ring δ13C and δ18O series. Two sites were selected, 40 km north and 8 km south of the Churchill River, to produce tree-ring δ13C and δ18O series extending from 1800 to 2009. Individual and combined isotopic results show significant statistical correlation with summer index discharge from three rivers near the Churchill (r = -0.61, -0.59 and -0.67 for δ13Cmean, δ18Omean and δ13C_δ18Ocombined, respectively; n = 41; p < 0.05; δ13C_δ18Ocombined series normalized with a z-score that integrates C and O isotope variations with the same weight). Therefore, summer index discharge has been reconstructed from the combined δ13C and δ18O data using a linear regression model. The resultant discharge series agrees with a discharge reconstruction ...
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