This data set contains two years of calibrated continuous in situ water vapour isotopic observations conducted since July 2015 in the east-Siberian Lena delta, at the research station on the Samoylov Island (72°22'N, 126°29'E). The temporal resolution of this data set is of 1 hour. The measurements have been performed with a Cavity RingDown Spectrometer located in a heated container outside the main station. The ambient air inlet is located at 5 m above the ground level. Calibration is achieved via the measurement of liquid water standards injected with a custom-made system including a vapourizer and a dew-point generator (bubbler).