Evaluation of climate changes impact on the hydrological behaviour of the peaty mediums - Application to the Haute Lesse-Ourthe area (Belgium).

The peaty and wet mediums have a very important role to play in term of biodiversity conservation, hydrologic pattern regulation, fauna habitat and landscape value. In the Haute Lesse – Ourthe catchments (Saint-Hubert), numbers of these mediums were strongly modified by a drainage network. This drainage network was implemented to permit a forestry production focussed on the Spruce. It has severely disturbed the hydrological cycle.

The study consists in modelling the impacts of restoration practices carried out notably within the framework of the LIFE European project on the hydrological behaviour of the peat bog. Then we modelled the effect of climate change.

Physical properties and retention curve of peaty materials were characterized on the basis of undisturbed samples using the Richards’apparatus.

Calculations were carried out with the hydrological model EPICgrid (GxABT). The model was initially validated on several reference catchments of the study zone. It was then applied at local scale for various peaty mediums (peat type, drainage characteristics, vegetation type) and for current and future climatic conditions. A regional simulation was finally carried out in order to evaluate the impacts of peat bogs restoration measures at catchment scale.

Simulations highlighted the differences in physical and hydrous properties of the different peat types (“true” peat and “degraded” peat). Local and regional impacts of peat bogs restoration on their hydrological behaviour have been evaluated. Eventually, simulations allowed us to evaluate climate change’s impact on the hydrological behaviour of the peaty mediums. The model showed notably that future climatic conditions could generate severe droughts which can become critical in some situations.