AgrHyS (response times in AgroHydroSystems), certified as Environment Research Observatory in 2002, is managed by INRA Rennes in collaboration with CNRS and Rennes Universities. It comprises two sites:

  • Kervidy-Naizin in Morbihan, monitored by Cemagref since the establishment of Naizin BVRE (Bassin versant représentatif et expérimental) in 1970, in the Coët Dan watershed defined by the Stimoes outlet (12 km2) then by INRA at Kervidy outlet from 1993 onwards (5 km2 sub watershed). Loamy soils, with gentle slopes and hydromorphic features downslope near the stream are underlain by Brioverian shales. Average annual rainfall (1995-2016) is 843 mm (+/-202). Average annual discharge (1995-2016) at Kervidy outlet is 348 mm (+/-163) and stream usually dries up in summer. Land use is mainly agriculture, (>90%) typical of multicrops-livestock intensive farming with dominance of dairy farms and enclosed pig production, and comprises about 60% of arable land (maize, cereals) and 30% grasslands (rest being housing, roads and woods).
  • Kerbernez in Finistère hosted INRA agronomic experiments since 1978 where six small watersheds of 10 to 60 ha have been monitored since 1992. Soils are loamy sands, hydomorphic in valley bottoms, and are underlain by granitic bedrock. Annual rainfall (1998-2016) is 1125 mm (+/-219) and streams are permanent for most of the watersheds (average 200 to 400 mm/year over the period 1998-2016). Agriculture, multicrop-livestock farming, mostly dairy farms, is declining since the late 90s.

AgrHys is dedicated to the observation of agro-hydrosystems affected by the dramatic evolutions of agriculture since the end of the 1960s. The central question of the observatory is the response time of these systems to such changes and to climate variability. Research questions and monitored variables have evolved during the past 50 years, and the long time series produced allowed to test hypotheses and produce knowledge notably on concepts such as variable source areas, buffer zones, spatial organization of soils, characterization and modelling the role of shallow groundwater on nitrogen transfer, characterization of stream flow particulate phase and quantification of storm event exports, assessment of the atmospheric component of C and N cycles, emergent pollutants and biodiversity in agro-systems. Currently, observations aim at contributing to a systemic, integrated and spatialized understanding of rural landscapes. Water and major element fluxes (carbon, nitrogen, phosphorus) are monitored in the soil/surface water and groundwater/atmosphere continuum. Analyses are either carried out in the lab on grab samples (water traps, piezometers, stream, rain, atmosphere, …) or as continuous in situ measurements (in-stream high frequency probes, gaseous fluxes). Evolution of agricultural systems, land use and practices is documented through farmer surveys or reconstituted from satellite remote sensing. Monitoring of the biological component includes soil and water microbiology, soil macro and meso fauna and aquatic invertebrates.

The objective of current and future research is to address scaling issues (extrapolation of knowledge acquired on small research watersheds to the river basins at the regional scale) and also to study the factors controlling the transfers and stocks of C, N, P while accounting for the synergies and antagonisms between these elements.

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