What are some water sources that not be easily used to supply human water needs?

Fresh water sources that are not readily available for use are ground water and water in polar glaciers.

Fresh water is one of the most important resources on earth. Unfortunately, freshwater is a very scarce resource. This is because, most of the earth's freshwater resources are not readily available.

About 69% of the fresh water on earth is present as ice in glaciers and are not available for use. Another 30% of freshwater resources lies underground as ground water and is also not readily accessible for use.

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Atmospheric water source because are not available all the time,also they can not easier harvested inseady they required to fall up to ground (juvenile water) or surface water(ocean,lakes..etc) and be harvested