About Isotope hydrology

Isotope hydrology is a field of hydrology that uses isotopic dating to estimate the age and origins of water and of movement within the hydrologic cycle. The techniques are used for water-use policy, mapping aquifers, conserving water supplies, and controlling pollution. It replaces or supplements past methods of measuring rain, river levels and other bodies of water over many decades. Water molecules carry unique fingerprints, based in part on differing proportions of the oxygen and hydrogen isotopes that constitute all water. Isotopes are forms of the same element that have variable numbers of neutrons in their nuclei. One commonly cited application involves the use of stable isotopes to determine the age of ice or snow, which can help indicate the conditions of the climate in the past. Another application involves the separation of groundwater flow and baseflow from streamflow in the field of catchment hydrology. The signatures of subsurface water can also be identified by well sampling, the composite signature in the stream is an indicator of, at any given time, what portion of the streamflow comes from overland flow and what portion comes from subsurface flow.