Outstanding result / New tools for managing groundwater resources

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Saint-Michel reservoir in Brennilis. © EPAGA

Climate change is creating structural challenges for water resource managers, with water shortages; more frequent periods of drought with a possible economic impact in the medium and long term, and difficulties in maintaining hydrological conditions that are favourable to biodiversity in watercourses. In particular, climate change and extreme events raise new problems for all the players involved in supplying drinking water: communities of municipalities, water utilities, catchment basin entities, economic stakeholders, etc., and more generally the public at large. All too often, these problems are still addressed from the standpoint of local water supplies, whereas in reality, they can only be effectively solved through a broader approach.

Brittany is a case in point. The region has experienced an unexpected increase in drinking water consumption over the past three years, with a rise of between 8% and 10% on the previous decade. At the same time, it has seen a trend towards drier periods in the autumn.

In response, BRGM is developing two projects. “De l’Eau pour Demain” is a regional project set up to improve knowledge of needs and resources. It is running in synergy with the interregional project “Water for Tomorrow”, whose purpose is to develop a decision-support tool to secure drinking water supplies across six groups of communes in southern Finistère.

“De l’Eau pour Demain”: knowledge and understanding of the impact of climate change on water resources

“De l’Eau pour Demain” is a project launched in 2021. Funded by the Loire Bretagne Water Agency, the Regional Council of Brittany and BRGM, it brings together Brittany’s three departmental drinking water utilities for a joint technical project with the Finistère departmental council and BRGM. The aim is to improve knowledge and understanding of the impact of climate change on water resources in Brittany.

The first phase of the project aims to develop a better understanding of the consumption of public drinking water supplies and user behaviour, and also to characterise the vulnerability and resilience of the water resources on which these uses depend. It should allow an assessment of the data available on consumption (needs), the consumption mechanisms at work during drought episodes and the resources available.

The second phase of the project seeks to gain a clearer understanding of how water resources (dams and groundwater) respond to climate-related constraints, in order to improve the quantitative management of drinking water resources and infrastructures, particularly in crisis situations (drought). A hydrogeological study will also be carried out to determine the aquifers that are most resilient to drought and identify the sectors to be prioritised in searching for new groundwater sources.

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Maps showing shortfalls in drinking water supplies in August based on different scenarios and with demand continuing to rise through to 2050 (green = no shortfall, red = 50% shortfall, black = 100% shortfall). © BRGM

“Water for Tomorrow”: innovative tools and approaches for water management

The project is taking place on three pilot sites in the UK and two in France, one of which is in southern Finistère. Funded by the European Interreg programme, the project is seeking to develop and test innovative tools and approaches for water management. This should enable more responsive short-term management of drought episodes, and better long-term planning of investments and water management at regional level. At the southern Finistère pilot site, a hydro-economic model of the drinking water supply system had been built jointly and used on a participatory basis with regional stakeholders. This exploratory decision-support tool makes it possible to assess the impacts of a number of medium or long-term scenarios for the region.

In its first phase, the model made it possible to plan for shortfalls between resources and needs based on different future scenarios. These shortfalls have been quantified and localised. The second phase has provided a basis on which to assess the efficiency of various adaptation measures – singly or combined – in order to respond to expected future vulnerabilities, and thereby to initiate a collective management strategy.

This is an innovative tool for developing collective planning of drinking water supplies, bringing together players who were not necessarily used to working together.

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