Assessment of hydrogeological monitoring for the Montpellier water board (3M)

3M (Montpellier Méditerranée Métropole) uses several sources of water to supply its municipality. The most important is the Lez, the 3rd largest in France, which alone supplies more than 200,000 people. However, it is located in very calcareous formations known as karst, making it highly vulnerable to drought.

They have around twenty measuring points, which have been observed for some twenty years. As part of its regulatory monitoring obligations, 3M selected ImaGeau to carry out the hydrogeological monitoring of the Lez spring for the period 2019 to 2023.

The main need was to complete and optimise the existing tools for more accurate and exhaustive monitoring of changes in the water level.

We monitored data from the various piezometers to study the behaviour of the karstic reservoir in relation to meteorological events. Thanks to this regular gathering of information, as well as that collected from the Hérault departmental council and Prédict, we are now in a position to draw up an accurate annual hydrogeological report on the state of the Lez spring.

To complement this conventional monitoring, we have set up our EMI solution to monitor data from the various measurement points spread over an area of almost 500 km² in real time.

Many municipalities and inter-municipalities are located within this perimeter, and the Lez karstic reservoir is not only used by 3M. Poor water management can lead to conflicts of use. To avoid this, each of the stakeholders needs to know how much water they can use, based on what is available at any given time.

Real-time access to piezometric data via EMI provides a high degree of transparency on the state of the water table, and important information for adapting the management of this resource.

We carried out a full assessment of the existing 3M tools, to check their reliability and recalibrate them where necessary. This gave us a more accurate picture of the water level.

Since then, our team of hydrogeologists has made regular visits to each piezometer to check that the probes are still collecting interpretable data, and to recalibrate them if necessary.

Very satisfied with the monitoring carried out since 2019 on the Lez spring, 3M has decided toextend the monitoring of its data to all their drinking water production catchments. We are now monitoring all their boreholes with the EMI application, and not just the Lez.

This expansion is the result of imaGeau’s ability to establish a connection between groundwater levels and weather conditions in real time, thanks to EMI. Combined with theinterpretation of these data by our hydrogeologists, this approach has enabled us to go beyond the methods previously used with other consultancies, offering more qualitative and comprehensive results.