WHAT KINDS OF ROCKS YIELD GROUND WATER?
Ground water is most readily obtained from saturated rocks that have fairly large openings between grains (such as sand, gravel, and sandstone) or have interconnected cracks or channels (such as limestones). Rocks that contain ground water and that will yield it to wells are called aquifers. Sand and gravel beds are widely used aquifers in Illinois.
Figure 19—Source, movement, and occurrence of ground water. Arrows in aquifers show direction of flow of water.
EVAPORATION SAND AND GRAVEL WELL Water Table River sand and gravel ARTESIAN WELLS EVAPORATION River WELL COLLECTING AREA FOR ARTESIAN WATER PRECIPITATION Crater WATER TABLE WELL Lake Glacial pebbly clay Glacial sand and aquifer Shale Sandstone aquifer Limestone aquifer Shale GROUND-WATER RESERVOIR