plenty of water must be available nearby to form a geyser or a hot spring. Scientists can perform many different tests on the composition of water to determine its origin. Some of these tests involve isotopes . Water is made up of bonded oxygen and hydrogen elements. The first element, oxygen, comes in different forms, called isotopes. These isotopes can sometimes tell the history of the water. Hydrogen, the other element in water, also takes different forms, and it, too, can provide information about water. For instance, scientists have used these methods to determine that water in geysers and hot springs often is several hundred years old. Isotopic studies also indicate that most of the water found in a geyser system is meteoric water (atmospheric water reaching the Earth as precipitation).
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