Desalination and isotope hydrology

With ever increasing demand for fresh water, the need to look at new sources of water is becoming imperative. Isotope hydrology is a powerful technique to explore such new sources of ground water and to also understand the origins of contamination of water. The sea is also becoming important as the only perennial source of water. Moreover, groundwater is increasingly becoming saline due to over-withdrawal, and there is a need to improve its quality. Desalination is the process that removes salts from water or water from salts, the end objective being fresh water. The former represents the case where it is the minor constituents that are actually removed-as, for example, in electrodialysis-whereas the latter would represent the case of removing the major constituent, i.e., water itself, distillation being the most common example. Despite the seeming attractiveness of removing minor constituents, the reality is that in most approaches to practical desalination it is the major constituent, i.e., water, which is removed. The presentation will dwell on the twin aspects of identification of newer ground water sources and also increasing the public water supply through desalination. More particularly, our focus will be on the science behind the technologies of isotope hydrology and desalination. Given that desalination requires external energy input, the available options for desalination will be shown to rest largely on the appropriateness of energy supply and the level of sophistication of operation desirable. (author)