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Estimation of the base flow time constant for global scale applications

Abstract : The base flow time constant (τ) represents the mean amount of time the groundwater takes to reach the stream from the recharge zone in a given watershed. τ is a key element to simulate base flow in simple groundwater models as ORCHIDEE. τ was estimated at global scale based on a solution of the Boussinesq equation for unconfined sloping aquifers. τ depends on the effective porosity, transmissivity, aquifer slope, and drainage density (δ). When estimated from global available datasets, τ results are overestimated when compared to recession analysis results. A sensitivity analysis showed that transmissivity and δ are the main uncertainty sources of τ. A river network extraction based on lithology, climate, slope, and observed δ allowed to obtain δ values close to reference data and spatially variable at regional scale. The use of a new δ and the combination of two hydraulic conductivity datasets of soil and aquifer reduced τ of two orders of magnitude, however the values remained overestimated. The use of τ in ORCHIDEE land surface model showed a strong sensitivity of the river discharge buffer effect to τ, which worsen simulated river discharge when compared to observations. This methodology needs more adequate porosity and transmissivity values when compared to global available datasets that will result in close results to observed river discharge.
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Submitted on : Monday, November 13, 2017 - 10:05:09 AM
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  • HAL Id : tel-01633500, version 1

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Ana Claudia Schneider. Estimation of the base flow time constant for global scale applications. Hydrology. Université Pierre et Marie Curie - Paris VI, 2017. English. ⟨NNT : 2017PA066132⟩. ⟨tel-01633500⟩

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