In this study several water compartments (precipitation, creek, soil) were sampled over a two-year period on a bi-weekly basis from April 2017 to April 2019 and analyzed for the temporal variations of their oxygen and hydrogen stable isotope ratios (δ18O and δ2H) at five sites over an elevation gradient from sea level to around 1600 m a.s.l. on the Mediterranean island of Corsica (France). Sampling site code is composed of the mountain ridge side (W for west, E for east) and the approximate elevation (L for low, M for mid, H for high). Precipitation was collected via evaporation-free, tube-dip-in water precipitation collectors (Palmex d.o.o., Zagreb, Croatia). Creek water samples were taken mid-stream. Where possible, soil suction probes were installed at around 80 to 100 cm depth. If the topsoil layers were too thin or rocky and a soil probe installment was not possible, water from roadside springs and fountains, or rockface seeps was sampled. Probe, fountain, and seep water are referred to as 'underground' water.