Temporal patterns of water quality: decadal high-frequency data-driven analysis from an hydrological observatory under agricultural land-use

The article synthetises PhD research on hydrological and hydrochemical data analyses from Kervidy-Naizin agricultural catchment (belonging to the Environmental Research Observatory AgrHys, itself part of the RBV network of French hydrological research catchments). Due to water quality and climate change issues, the catchment was heavily monitored as early as 2000. The data-driven analyses presented hereafter consider for the first time the whole 12-year long dataset. Such outstanding time-series enabled to address the following questions: which hydrological processes are controlling solutes exports in the catchment? How does the wetness state dynamic influences these dominant processes? Four original methods are used covering the range of temporal variability from flood event to seasonality and its inter-annual variations. A solute export conceptual model, composed of four hydrological compartments was proposed to explain the diversity of export dynamics for the catchment. Years presenting extrem hydro-meteorological conditions support this model, and emphasise on the importance of the change of catchment wetness state. Flood events also depend on that. Lastly, downslope advection and dispersion as well as riparian production, retention or mixing are also no negligible processes taking place in the catchment. Water quality signal is well structured in time and its structure is now further understood. The signal, strongly impacted by the agricultural use for given solutes, is dominated by seasonality but varies according to yearly hydrometeorological conditions. Comparing the solute export conceptual model built on Kervidy-Naizin to other catchments would be interesting to pinpoint driving factors.