Figure 9.22
The varying height of the water table. Permanent lakes and streams indicate the local height of the water table. (A) The Um El Ma Oasis in the Sahara, in southwestern Libya. Oases form where a depression in the sand dunes dips below the water table. Although almost no water falls from the sky, there is water stored in the aquifer just below the sand surface. (B) In humid regions, drought can lower the water table. Standing bodies of water can disappear if the water table drops.(A. © Frans Lemmens/The Image Bank/Getty Images)