Data for: Seasonal and event-based concentration-discharge relationships to identify catchment controls on nutrient export regimes

The water quality parameters included in this database were nitrate (NO3-), total phosphorus (TP) and soluble reactive phosphorus (SRP). From approximately 10 000 water quality stations present in the French national public database (http://www.naiades.eaufrance.fr/), we selected the stations meeting all the following criteria: i) C station can be paired with a Q station (data from http://www.hydro.eaufrance.fr/) when their catchments share at least 90% surface area; ii) all C catchments are independent; iii) C data contains at least 50 observations after outliers removal (i.e. values over 200 mgN L-1 and 5 gP L-1) over the period 2008-2015; iv) at least 30% of C observations occurred during “major” hydrological events (defined here as Q(t) > 1.5 x Q_baseflow); v) trends on C are non-significant over the period (p-value of Sen’s Slope test > 0.05, following Hipel and McLeod (2005)). Finally, stations where a single concentration value was observed more than 15% of the time were removed from the selection, a situation often seen in P surveys when concentrations are below quantification limits. This resulted in 219 unique catchments with respectively 179, 138 and 107 individual time series for NO3-, TP and SRP.