Streamflow elasticity as a function of aridity

Abstract. Relating variations in annual streamflow to a climate anomaly, commonly referred to as streamflow elasticity to climate, is central for a rapid assessment of the impact of climate change on water resources. This elasticity is classically estimated via a multiple linear regression between anomalies in streamflow and climate variables. However, this approach does not explicitly account for the fact that elasticity depends on aridity as suggested by “Budyko-type” water balance formulas. Using a large dataset of 4,122 catchments from four continents, we first verify empirically the link between elasticity and aridity. Then, we propose a method to constrain elasticity coefficients with derivatives from a “Budyko-type” water balance formula, that allows introducing an explicit dependency between elasticity and aridity. We show that adding this dependency produces a regionalized elasticity formula with physically-realistic elasticity coefficients.