Présentations Colloques

    Session 8.10: Recent developments in groundwater modeling and mathematical tools in Hydrogeology
    Schneider Ana
    Estimation of the base flow characteristic time scale for global scale applications
    Base flow from aquifers to rivers is a key element of the water cycle, and is particularly important to drought resilience. The base flow characteristic time scale (tau) is an important variable to estimate base flow in regions with no discharge measurements, in simple groundwater models such as the ones embedded in global-scale land surface models, and it can provide an indirect index of groundwater vulnerability. Tau represents the mean amount of time the groundwater will take to reach the stream in a given catchment. Here, we estimate tau using a long-term solution of the Boussinesq equation in an exponential form. It depends on effective porosity, effective transmissivity, and the mean distance from the stream to the divide (estimated based on drainage density). Global porosity and estimated transmissivity used in this work are derived from GLHYMPS (high resolution porosity and permeability data). Global drainage density was calculated using global high-resolution river network extracted from HydroSHEDS data at 15 arc-seconds, constrained by lithology, climate, and observed drainage density. Tau results are presented as means within 7.5’ x 7.5’ grid-cells with a global coverage, and compared with alternative estimates, at multiple scales. We also show that the main uncertainty factor of tau is the drainage density, which was improved, and significantly reduced, by our methodology compared to state-of-the-art estimates from available global DEMs.


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