[paul.fr]

Why does underground water not dry up due to the heat, and why when it's extracted from wells or bore holes is in not laced with sand?


[MOD - subject altered to make it a question - CS]

[Bass]

Surface temperatures vary over a wide range in deserts, but dig down a few feet and temperatures remain much more constant- so less chance of evaporation.  Most wells in sands are cased (otherwise they would collapse) to keep the sand out.  Also, sand is more dense than water, so not as easily lifted to the surface.