Here you get an overview of the most commonly used stable and unstable or radio-active isotopes in hydrology. In red marked are those which are analysed more frequently. The most frequently used isotopes include the heavy isotopes of the element of the water molecule hydrogen and oxygen. And of the element carbon, occurring in water as constituency of desolved inorganic and organic carbon compounds.
The mentioned Deuterium, O-18 and T-13 are stable isotopes of the respect elements, whereas Tritium and C-14 a radioactive isotopes of the respective elements, characterised by their specific half-life.