Water stress: the city of Nantes relies on the EMI solution to maintain its water production capacity

As water stress increases, maintaining drinking water production capacity is becoming more and more challenging for local authorities. But professional solutions do exist. They help to clarify the issues and guide the choices involved. To manage its water resources, the City of Nantes and its water supply company Vignoble Grandbleu Basse Goulaine have enlisted the services of experts, and opted for the EMI app developed by Saur Group company ImaGeau.

Extensive areas of France suffered periods of drought with zero rainfall during summer 2019. Throughout this period, exceptionally high temperatures triggered a series of heatwaves. As a result, 89 departments of mainland France had no choice but to restrict water use on a number of occasions. According to meteorologists, this manifestation of water stress is bound to become more frequent as a result of climate change, but we should not lose sight of the fact that drought is just another feature of climate that can be exacerbated or mitigated by the water management policies we adopt.

In this context, the water resource management plan implemented by the City of Nantes is particularly instructive.

Example of water resource management

The droughts of summer 2019 spared neither the City of Nantes nor its surrounding region. During that period, water levels in the River Loire fell to historically low levels, and its flow rate was the lowest recorded in the Loire-Atlantique region since 1976. There were only two years in the last 150 when water levels fell this far in July: 1870 and 1949!

Nevertheless, the local authority remained confident in its ability to supply water to the urban community and its 950,000+ residents despite the fact that the high population density of Nantes means that its water is abstracted from the alluvial water table of the River Loire.

In fact, there are no fewer than 11 boreholes at the Basse-Goulaine production site. They draw water from the sand and gravel strata below the bed of the river; a geological formation that often causes problems for the system due to the presence of minerals such as iron and manganese, which have the unfortunate tendency to precipitate in the water and accumulate in the form of blockages within the boreholes.

Given the increasing frequency of water stress events, this issue could no longer be shrugged off, so early in 2018, the local authority decided to work closely with ImaGeau on building a plan for continual monitoring of these boreholes. This Saur Group company has developed the EMI app to predict the risk of drought and ensure optimum operation of water production facilities. “By providing the right information at the right time,” as Matthieu Baïsset explains.

Expert support for making the right choices.

At the same time, ImaGeau consultants worked closely with the operator to support their decision-making, help with implementation of optimization measures (borehole regeneration cycle, pumping cycle, etc.) and provide continuous monitoring of the drought risk. The app itself also generates regular reports on the local situation and production facility parameters.

The example of how the City of Nantes approaches its management of water resources demonstrates how operational support from experts and a level of investment appropriate to the needs of the installations can enable production capacity to be accurately controlled, and even guaranteed. The answer is to predict the risk of drought using real-time processing of stable, reliable data, accompanied by more effective operating practices.