In arid and semi-arid regions, evapotranspiration rates are much higher, recharge is less, flow paths longer and residence times much greater and hence much higher levels of natural mineralisation, often dominated by sodium and chloride, can be encountered. Thus the major ion contents and TDS are often high. In some desert regions, even if groundwater can be found it may be so salty (extremely high TDS) as to be undrinkable, and the difficulty of meeting even the most basic domestic requirements can have serious impacts on health and livelihood. .
