<P> Fluid balance is key . Profuse sweating can increase the need for electrolyte (salt) replacement . Water intoxication (which results in hyponatremia), the process of consuming too much water too quickly, can be fatal . </P> <P> Water covers some 70% of the Earth's surface . Approximately 97.2% of it is saline, just 2.8% fresh . Potable water is available in almost all populated areas of the Earth, although it may be expensive and the supply may not always be sustainable . Sources where water may be obtained include: </P> <Ul> <Li> Ground sources such as groundwater, springs, hyporheic zones and aquifers </Li> <Li> Precipitation which includes rain, hail, snow, fog, etc . </Li> <Li> Surface water such as rivers, streams, glaciers </Li> <Li> Biological sources such as plants . </Li> <Li> Desalinated seawater </Li> <Li> Water supply network </Li> <Li> Atmospheric water generator </Li> </Ul> <Li> Ground sources such as groundwater, springs, hyporheic zones and aquifers </Li>

Where is water used for drinking most likely to come from
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