Ernie Lightman, age 10  Toronto for his question:

What makes an oasis?

We tend to think that no water falls in a desert, Actually there is no place on earth that has no rain or snow, Whenever rain falls, a certain amount if it evaporates into the air, Generally most of it seeps into the ground or sets out to join streams and rivers, Over a desert it so happens that there is more evaporation than the average rainfall, For this reason few, if any plants can grow.

Generally a desert gets its rainfall in sharp showers. When it rains it pours in seeming torrents. Maybe this happens only once in four or five years, Such rainfall is not enough to feed a flowing river, The ground is drenched and much of the water seeps below. It settles with the ground water which is usually quite deep in desert areas.,

Here and there, the level of this ground water comes near the surface of the desert, It can be reached by digging a hole, The ground water seeps in to fill the holes making a little pool, This is the oasis where, the thirsty camels pause to drink and the weary travelers to refresh themselves in the shade of green palms.