Departmental network for quantitative monitoring of sources in the Pyrénées Haut-Garonnaises

In the Pyrenees, many sources are collected for drinking water supply. For a long time considered abundant, this resource had never been subject to quantitative monitoring. The summers of 2022 and 2023 marked a turning point: Several sources have seen their flow greatly decrease, some have even dried up. Faced with these findings, the need to better understand the evolution of flows over the long term has emerged, particularly in the context of the assessment of the effects of climate change. This monitoring is part of the [Projet de Territoire pour la Gestion de l’Eau en Garonne Amont] (https://garonne-amont.fr/) (PTGA). It constitutes action D.1.1 of the Garon’Amont programme: the creation of a hydrological source observatory. **The RESPYR 31 network** In partnership with the [Bureau de Recherches Géologique et Minières] (https://www.brgm.fr/fr) (BRGM), the Conseil départemental de la Haute-Garonne has launched a first phase of study to identify the sources to be followed. This network, called RESPYR 31 (Departmental Network for the Quantitative Monitoring of Underground Water Resources in the Haute-Garonne PYrenaes), comprises 18 selected sources, representative of the different types of aquifers, 12 of which are priority and 6 are complementary, according to hydrogeological, operational and feasibility criteria. Monitoring requires specific adjustments to be carried out either inside the catchments or downstream at the level of the streams from the sources not captured. Each site is equipped with a water height measuring probe, which makes it possible to calculate the flow through a measurement curve (the relationship between height and flow established by manual measurements). In 2024, three first sources were equipped: source of Castech in Estenos, source of Laouech in Milhas, source of Naou Hount in Bagnères-de-Luchon. Three new sources will complete the network in 2025. **Shared data** The probes shall measure: the flow rate (in real time), the temperature of the water, its conductivity (ability to transport electricity, linked to mineralisation). The data is recorded every hour (24 measurements per day) and transmitted automatically. They are updated every morning at 6:00 a.m. in this open data portal.