the Sahara desert is huge! it probably covers over 75% of northern Africa!
In the Sahara water is scarce and when you do find water it is almost always stagnet and contains harmful bacteria.
Humans have to ride on camels becuase they store water in their hump and don't consume as much water as a horse or mule would.
people that live in the sahara always wear sleeves and pants because it helps your body hold water because your sweat will saturate into the sleeves and keep you cool in the heat and your skin will absorb the water again.