Insights into the influence of morphology on the hydrological processes of river catchments using stable isotopes

Water isotopes (& delta;O-18, & delta;H-2) were systematically monitored in two river catchments to investigate the isotopic spatiotemporal variation and the differences between them. The Pinios River Basin (PRB) exhibited lower average & delta;O-18 and & delta;H-2 values (-7.9 & PTSTHOUSND; and -50.8 & PTSTHOUSND;, respectively) compared to the Evrotas River Basin (ERB) (-6.5 & PTSTHOUSND; and -38.2 & PTSTHOUSND;, respectively) but higher in range (3.3 & PTSTHOUSND; vs 1.2 & PTSTHOUSND; for & delta;O-18, respectively). The Bayesian modelling results showed higher groundwater contribution in the PRB (25-50%) than in the ERB (15-35%) relative to precipitation during the wet period. The isotopic spatial variability was attributed to the influence of local precipitation, evaporation and additional flow pathways (e.g. soil water). The correlation analysis showed that the isotopic composition is controlled by the catchment altitude, slope and discharge. This study highlights the catchment physiographic control on the isotopic composition of rivers, which can support strategies for better water resources management.