ABSTRACT
Piezometric time series data are the basic element necessary, although not always sufficient, for evaluating the quantitative status of groundwater bodies. This data must enable trends in the evolution of the water status, and in particular degradation, to be highlighted so that the necessary measures can be taken for sustainable management of the resource and to maintain the right balance between withdrawals of groundwater and preservation of the environment. The piezometric data must, therefore, be compared to water withdrawal data. In addition, the choice of piezometers is fundamental to the overall characterisation of groundwater bodies, given that most are dissimilar both in terms of structure and hydrodynamics. This paper presents the example of the piezometric network in the Seine-Normandy Basin, installed at the end of the 1960s by the BRGM. Different steps have resulted in the constitution of a relatively dense network (more than 350 stations), but with points unequally distributed throughout the basin and, in particular, of widely variable usefulness vis-à-vis the objective of evaluating the quantitative status of groundwater bodies. Work has recently been carried out in collaboration with DIREN (French Regional Environment Department) to analyse and rank the piezometers monitored by the BRGM. The ranking criteria were as follows: time series greater than 30 years, comprehensible hydrogeological operation, influence of watercourses, influence of pumping operations, uniqueness of the exploited aquifer and status with regard to the risk of silting up or drying up. This work will make it possible to define the piezometric network for monitoring the quantitative status of groundwater bodies as defined by the Water Framework Directive. The last part of the paper presents an example of the use of piezometric data for the management of groundwater in drought periods.
