Water: tapping into the old and the new
Naturally-occurring isotopes are being used to determine the extent of African aquifers so that water resources can be managed more efficiently. Calculating the ratio of isotopes present in a sample of water can provide hydrologists with information on the 'age' of the water and its origin.
For instance, ground water in the drought prone region of Moyale, Ethiopia,
was discovered to contain tritium (3H) - the radioactive isotope of hydrogen
which was mainly produced during the atmospheric bomb tests of the late
'50's/early '60's. The presence of this isotope indicates
that the water is a young, renewable resource which can be exploited for water
extraction. However, other areas in the region were dated using radioactive
carbon-14 (14C) indicating that these reservoirs contained only
'paleowater' (rainwater from 6000 years ago).
Like
any other ancient and non-renewable resource, extraction of this water is known
as 'mining' and extraction rates have to be monitored very carefully
if the reservoir is not to run 'dry'.
The largest known groundwater resource in the world is the Nubian Sandstone aquifer in Egypt. This also contains paleowater but is so plentiful (the aquifer covers tens of hundreds of km2) that it is unlikely to be depleted by extraction in the forseeable future. This water will be vital in supporting two million people and 50,000 hectares of 'reclaimed' land on the fringes of the Sahara.
Hydrology data generated by isotopic techniques can provide essential information for national water authorities wishing to manage their resources more effectively.
