The ORACLE research observatory is one of the oldest French observatories of the critical zone. It is located in the Paris basin (70 km east of Paris). The observatory is constituted of three catchments: Grand Morin, Petit Morin, two tributaries of the Marne River (1,800 km² area) and Orgeval catchment (104 km²), tributary of the Grand Morin, smaller but with most of the instrumentation. The topography consists of the Brie plateau (130 m asl) incised by valleys (80 m asl). The sites are subject to temperate oceanic climate (average annual temperature of 11.3 °C and annual precipitation of 740 mm). The geology corresponds to a sedimentary basin with an alternance of clay and limestone layers (including Brie limestone hosting the aquifer of the same name) covered with a silty layer where deep soils develop. The land is mainly agricultural, representative of the intensive cereal crops of the Paris basin. The soils are hydromorphic, mainly drained by subsurface drainage networks.
Starting year: Hydrological data since 1962 and water quality since 1975.
Location: 70 km to the East of Paris
Keywords: Hydrology, bio-geochemistry, intensive agriculture, agricultural subsurface drainage, sedimentary basin.
The ORACLE sites are representative of sedimentary basins and artificially drained hydromorphic soils, in the context of intensive agriculture, changes in agricultural pratices and climate change.
Since its creation in 1962, for floods and weathering issues, the observatory was able to evolve towards other societal and environmental issues. The problem of diffuse pollution of agricultural origin, initiated in 1975, has contributed to a better understanding of the interactions between agricultural activities and the chemical quality of surface and ground waters. Since the 2000’s, the problem of pesticides and scientific questions linked to biology and biodiversity have been added. It is also an exploratory workshop for technological innovations, such as high frequency measurement in biogeochemistry.
ORACLE’s observations support the development and use of numerical models for impact studies and territorial management.
Sites and measured variables
The ORACLE observatory implements a multi-scale observation strategy (from 1 km² to 1,800 km²), thanks to the nested instrumented sub-catchments, to address a range of challenges. The meteorological, hydrological or chemical data are obtained thanks to 80 measurement stations. They allow for long-term observations at different time intervals (hourly, daily or weekly) of precipitation, surface and ground waters. Almost 34,000 data are collected monthly.
The main instrumental apparatus consists of:
- water level and discharge stations located at the outlet of each sub-catchment,
- piezometric stations installed in the Orgeval catchment along the plateau-valley axes,
- rainfall stations supplemented by those of Météo-France,
- meteorological stations for air temperature, humidity and radiation measurements,
- soil moisture measurement stations from the soil surface to 1.5 m depth,
- water sampling stations for water quality measurement (dissolved organic and inorganic carbon, conductivity and nitrate concentrations), including a RiverLab prototype developed as part of the Equipex CRITEX, installed in June 2015 at the outlet of Avenelles (within the Orgeval sub-catchment) for a high-frequency measurement (every 30 minutes) of the chemical composition of the river.
Partners and further information
Since 2011, the ORACLE observatory has been organized around the “GIS” scientific structure, bringing together 8 member institutions (INRAE, Sorbonne University, CNRS, AgroParisTech, Mines Paris Tech, the Regional and Interdepartmental Directorate for the Environment, Planning and Transport – DRIEAT IdF, Météo France) and 14 research units and departments. It is part of the experimental platform of the Federation of Île-de-France and Research in the Environment (FIRE), as well as the Zone Atelier Seine through the Interdisciplinary Environmental Research Program on the Seine Basin (PIREN Seine).