This paper focuses on the relation between the structure of a constructed Technosol and its hydraulic characteristics during its early pedogenesis. The method is based on a 3-yr comparison of, on one hand, experimental measurements from an in situ gravitation lysimeter and, on the other hand, a modeling approach with HYDRUS-1D. The change of water flow patterns with time was described. It was consistent with previous results for constructed Technosol aggregation. Apart from seasonal variations, the specificity of the hydraulic functioning of the constructed Technosol was shown to be due to the nature of its technogenic parent materials. The in situ evolution of the hydrodynamics has been established and partly linked to external factors (climate, vegetation). The direct modeling and the optimization of the parameters over first a 3-yr period and then three 9-mo periods accurately represented global water flow trends at the pedon scale. However it failed to simulate precisely the main events, such as massive leachate outflow. An evolution with time of some of the hydraulic properties was shown, expressing the structuring of the soil. The existence of two distinct time-scales (slow and steady/fast and cyclic) of the evolution of hydraulic parameters was then formulated as a new hypothesis.