During high flow as in SC2, the water isotopes were influenced by the changes in the isotopic composition of precipitation indicated with the lighter isotopic composition in all the stations compared to SC1 (Table 1, Fig. 4). It is to be noted that the monthly mean water isotopic values in the catchment precipitation over the past decade (2004–2014) (measured by FOEN-ISOT monitoring at St. Gallen) varied seasonally (showing depleted signatures from January–April and enriched signatures in July–August), with 8‰ annual variations in d18O-H2O (Fig. S2).