Estimating travel time of recharge water through a

Authors: Samuel Mattern Marnik Vanclooster

Publish Date: 2009/08/28

Volume: 10, Issue: 1-2, Pages: 121-135

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Abstract

We estimate the travel time of percolating water through a deep vadose zone at the regional scale using a transfer function model and a physical based conceptual flow model Hydrus1D thereby exploiting the time series of precipitation actual evapotranspiration and groundwater piezometry and generic vadose zone data With the transfer function model we observe a high variability of estimated travel time varying from 09 to 31 years corresponding to estimated vertical water flux velocities varying from 66 to 280 m/year These results were compared with the travel time estimated from the physical based conceptual model With the flow model estimated travel time varies between 47 and 155 years corresponding to water flux velocities varying between 17 and 41 m/year The estimated travel time calculated with the flow model were therefore about five times larger than those estimated with the transfer function model This could be explained by the fact that the transfer function model considers heterogeneous recharge from the vadose zone as well as from the vicinity of the piezometer through the so called “pushing effect” In addition the flow model requires various hydrogeological and hydrodynamic parameters which were estimated using generic parametrisation approaches that are largely affected by uncertainty and may not reflect the local conditions In contrast the transfer function model only exploits available measurable time series and has the advantage of being sitespecific

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