The need
In view of the challenges involved in sharing water across the region, the Alpilles Regional Nature Park wanted to find out more about groundwater resources, for both prospective and operational purposes. This survey is a preliminary requirement to setting up an observatory for the quantitative and qualitative monitoring of resources. In the longer term, the observatory will become the main tool for guiding resource management with a view to limiting tensions and potential conflicts in use.
As part of the geological survey of the massif, BRGM sought to find out more about the geological history and formation of the massif, and to establish the properties of the reservoirs formed (geometry and characteristics, inventory of hydrogeological phenomena such as springs, losses and karstic processes).
Taken from the brochure published by the Alpilles Regional Nature Park, based on the results of the survey (2022)
© PNR Alpilles
The results
A map and representative log of the massif, with three cross-sections, drawn up using fieldwork data. The results of the survey show that the Alpilles Massif contains five major potential reservoirs:
- Two reservoirs of effective fissural porosity, of the fractural or dominant dissolution type (“high permeability”):
- The major reservoir formed by the Lower Cretaceous (Upper Hauterivian) limestone underpinning the relief of the axis of the massif from east to west, and the southern part of the Baux Valley.
- The reservoir of Upper Jurassic/Lower Cretaceous formations, comprising Les Opies and, further south, the centre of the Anelier anticline.
- Barremian limestone (Urgonian limestone) found in outcrops along the northern flank of the Alpilles massif. The limestone is criss-crossed by scarps with several rising perennial springs, particularly on the southern flank of the massif.
- Limestone, calcarenite and molasse from the Tertiary period underpin the relief of Baux-de-Provence and other areas, again with perennial springs rising at their base.
- Two reservoirs where effective porosity is primarily matrix (“low permeability”):
- One reservoir where effective porosity is predominantly matrix, made up of modern quaternary formations covering the bottom of the lower parts of the massif (plains and valleys).
Using the results
The survey provides the Alpilles Regional Nature Park with a knowledge base on which it can develop its strategy to find new water resources and raise public awareness of water and its uses in the Alpilles Massif.
The Alpilles Regional Nature Park produced a mock-up based on one of the cross-sections produced during the survey, as well as a brochure for the general public, both of which were shown at the public workshops attended by BRGM in 2022.
The partner
- Alpilles Regional Nature Park
