Hydrological dataset on Mediterranean Catchments of the Real Collobrier Observatory for 1967-2024.

The Réal Collobrier hydrological observatory, located in south-eastern France and managed by INRAE (formerly Cemagref) since 1966, is a benchmark site for regional hydro-climatology. Created by the Ministry of Agriculture, its initial objective is to improve understanding of hydrological processes in Mediterranean regions underlain by metamorphic soils. The observatory’s catchment, situated in the Maures massif near the Mediterranean coast, is densely instrumented. Flow measurements are collected at the outlets of ten small forested nested catchments (ranging from 1.57 to 70 km²), including four headwater streams. A dense network of 15 rain gauges records rainfall data at a fine temporal scale. The dataset also includes climatological data, water temperature and soil data. The vegetation is dominated by forest communities on crystalline substrates (maquis of heath, cork oak, maritime pine, and chestnut). The geological formations are predominantly crystalline, with metamorphism increasing from east to west (from gneiss to schists and phyllites) [ 1 ]. Direct human influence has been negligible over the past 60 years, with land use and land cover remaining almost unchanged, except for a wildfire in 1990 that affected one small sub-catchment. All data presented in this article are available in the INRAE hydrological observatory's open database ( https://bdoh.inrae.fr/ ). The article describes the long-term dataset collected at the observatory and the validation procedures. The raw dataset underwent quality control, gap filling, and homogenization procedures to ensure temporal consistency and to improve data reliability. This rigorous quality control process results in a robust dataset used for research purposes. This well-documented hydro-climatic information can significantly advance understanding of hydrological processes [ [2] , [3] , [4] , [5] , [6] ], help validate and evaluate models in Mediterranean environments [ [7] , [8] , [9] ]. Given the non-perennial nature of rivers in this area, these data are particularly useful for studying the origin of intermittent flow, as well as the start and end dates of flow period [ 10 ]. The hydrological dataset now spans 58 years, offring the opportunity to evaluate long-term hydrometeorological trends [ 11 , 12 ]. Since 2019, observations of soil moisture at several depths have been added, providing valuable information on soil water availability and vegetation dynamics. The Réal Collobrier catchment area is part of the SOERE-RBV (Long-Term Observation and Experimentation System for Environmental Research – Mountain Basin Networks), which belongs to the OZCAR research infrastructure [ 13 ], certified by AllEnvi (National Research Alliance for the Environment) ( http://www.ozcar-ri.org/real-collobrier/ ).