Hydrology of the unsaturated zone

A better understanding of water transfer processes in the unsaturated zone (UZ) of soil is essential, whether for estimating the runoff/infiltration partition in hydrological models or quantifying groundwater recharge in hydrodynamic models used in hydrogeology.

This course will focus on practical work on soil columns in the laboratory. After a reminder of the equations governing the transfer of water and solutes in the NSA, an introduction to the modeling of transfers in the NSA will be given, using HYDRUS 1D software.

The practical exercises in this unit involve experimenting with water transfer in an unsaturated environment under controlled conditions (known rainfall intensity and duration, known drought period, imposed surface load, column of sand or reworked soil of known particle size), and continuously monitoring temporal changes in water content and water potential at various depths.

• Gain a qualitative understanding of the notion of capillarity in soil and its impact on infiltration processes.
• Understand the notion of water potential and water content in an unsaturated environment and how it changes following a rainy episode or a period of drought.
• Understand the relationship between water content and water potential.
• Estimate the volume of water infiltrated and the useful reserve based on water profiles before and after infiltration.
• Estimate evaporated flow and drained flow using the zero-flux plane method
• Calculation of a simple 1D hydrodynamic flow model in the NSA (with HYDRUS 1D)

Written exam (final test): 60

Oral (TP CR): 40