Modelling and simulation of a catchment in order to evaluate water resources

It is difficult for decision-makers to evaluate the impact of their territorial policies. Aspects to
be considered in this evaluation include those relating to humans, environment protection and
industry development. Two reasons explain the difficulty: decision-makers cannot specialise
in all domains implied in the process of decision and there is no simple tool allowing questions
such as “what would happen if…” to be easily answered.
Our work addresses this problem in the domain of water management at a catchment scale
and consists in evaluating water balances. We have developed a software framework
allowing simulation scenarios to be easily run and results about outlet flow and groundwater
variation to be easily interpreted. In this paper, we study anthropogenic scenarios consisting
in modifying the land cover at different scales: parcel, slopes or catchment. The simulation is
supported by a methodology allowing catchment models to be built up using a hierarchical
and modular approach based on components formalised by sequential machines. Few
modelling parameters are necessary because our purpose is not to build up a “perfect” model
to represent a catchment from a hydrological point of view but to illustrate the impact of
climatic changes or anthropogenic activities on water balance. The simulation interface allows
climatic data files to be selected to compare various scenarios. It allows the land-use to be
easily modified to understand the impact of anthropogenic activities on water from a
quantitative point of view. Modelling and results of simulation are illustrated on a catchment
located in the area of Cévennes (South of France).