Abstract 1. Introduction
1 Climate elasticity of streamflow revisited – an elasticity index based on long- 2 term hydrometeorological records 3 4 Vazken Andréassian(1), Laurent Coron(1,2), Julien Lerat(3), Nicolas Le Moine(4) 5 (1) Irstea, Hydrosystems and Bioprocesses Research Unit (HBAN), Antony, France 6 (2) now at EDF-DTG, Toulouse, France 7 (3) Bureau of Meteorology, Canberra, Australia 8 (4) Sorbonne Universités, UPMC Univ Paris 06, CNRS, EPHE, UMR 7619 Metis, 9 Paris, France 10 Abstract 11 We present a new method to derive the empirical (i.e., data-based) elasticity of 12 streamflow to precipitation and potential evaporation. This method, which uses long- 13 term hydrometeorological records, is tested on a set of 519 French catchments. 14 We compare a total of five different ways to compute elasticity: the reference method 15 first proposed by Sankarasubramanian et al. (2001) and four alternatives differing in 16 the type of regression model chosen (OLS or GLS, univariate or bivariate). We show 17 that the bivariate GLS and OLS regressions provide the most robust solution, 18 because they account for the co-variation of precipitation and potential evaporation 19 anomalies. We also compare empirical elasticity estimates with theoretical estimates 20 derived analytically from the Turc-Mezentsev formula. 21 Empirical elasticity offers a powerful means to test the extrapolation capacity of those 22 hydrological models that are to be used to predict the impact of climatic changes. 23 24 1. Introduction 25 1.1 About hydrological elasticity 26 In a context of growing uncertainty on water resources due to climate change, simple 27 tools able to provide robust estimates of this impact are essential to support policy 28 and planning decisions.
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