andyfettes wrote:
perched aquifers ? :idonno
LOL! Sorry Andy
let me see if this is easier:
Picture your bathtub is filled half way up with water, now pour in some dirt and rocks above that waterline to represent the ground, the height of the water remaining below the surface represents the water table.
Now at one end of the tub, make a big hill or mountain by piling it up even higher, somewhere in the top of that mountain bury a small soup bowl. This soup bowl represents a pocket of something impermeable, like bedrock or clay etc.
When you turn on the shower, which represents rain, most of the water will find it's was through the soil and level off at the water table. That soup bowl however will hold the water up above the water table.
Now, there is a pinhole, or a crack in that soup bowl, this represents a natural spring as the soup bowl drains through that crack, high above the water table.
Viola, a 'perched aquifer'