The AgrHyS (response time in Agro-HydroSystems) observatory is located in Brittany, a region with an oceanic climate. It includes two sites representative of the intensive agricultural systems of Western Europe, mixing animal and crop production.
Kebernez site (Plomelin, South Finistère) has a 1.3 km² area and is granitic with a rainfall of about 1,000 mm/year. It used for dairy farming and polyculture (rotation of corn, wheat, meadow).
Kervidy-Naizin watershed (Naizin-Evellys, Morbihan), is a second-order catchment with an area of 5 km², drained by Coët-Dan, a tributary of the Evel. It is developed on Upper Protezozoic (Brioverian) schist and rainfall is about 800 mm/year. Intensive farming (dairy and pig) is predominant. Coët-Dan stream is intermittent and and dries up from a few weeks to a few months between July and October.
Starting year: 1990-1995
Location: Brittany, South Finistère, Morbihan
Keywords: oceanic climate, granite and schist, intensive agrosystems, hydrology, biogeochemistry
The main question of the AgrHys observatory is the response time of hydro-geochemical flux to climatic and anthropogenic forcing within agro-hydrosystems. Catchments in Brittannyare disturbed by strong agricultural pressures involving modifications of water and biogeochemical cycles, especially the nitrogen cycle. This question is addressed through several actions of research focused on:
- Water transfer times within the Critical Zone and the recharge process of aquifers;
- Time scales of hydrological response to climate and anthropogenic changes,
- Modification of major biogeochemical cycles (carbon, nitrogen, phosphorus) at different time scales (from 1 month to 50 years) and the role of « hotspots » (wetlands, hedgerows),
- The influence of massive inputs of agricultural origin on biogeochemical stocks, catchment dynamics, chemical weathering and soil formation.
Sites and variables measured
The Naizin site is instrumented in the different compartments of the Critical Zone: atmosphere, soil, groundwater. Land use is monitored. The site has a meteorological station, a flux tower, 15 piezometers and a stream monitoring station for a high frequence monitoring of water quality at the outlet: biogeochemical measurements (carbon, nitrogen, phosphorus), suspended matter and turbidity. The installation of a « Riverlab » (Equipex « CRITEX » funding, 2012-2022) at the Naizin watershed outlet allows the collection and the analysis of high frequency biogeochemical variables (main ions, dissolved carbon)
Kerbernez site is composed of five sub-basins with an area ranging from 10 ha to 60 h. Puits basin is itself divided into three sub-basins . Measured variables include hydrological, hydro-chemical and climate data and enable the study of groundwater recharge dynamics. The site is highly instrumented and includes 7 limnimetric stations, 31 piezometers (placed at different depths), a set of 5 tensiometers, 1 meteorological station, weirs for flow measurements and 4 stations for a continuous measurement of soil moisture. Land uses are also monitored.
Partners and further information
The observatory is managed by the UMR Sol, Agro & Hydrosystèmes Spatialisation (SAS, Inrae-Agrocampus) of Rennes in collaboration with Géosciences Rennes. It is part of the OSU de Rennes-OSUR and it is supported by INRAE. The site collaborates with the Zone atelier Armorique (ZAAr), which is part of the network of Zones ateliers. AgrHys is integrated in the European (eLTER RI) and international (ILTER). Naizin site is one of the French sites participating in the European project eLTER PLUS of eLTER RI.