Hidden beneath the surface, groundwater travels through pores and fractures in soil and rock. Learn how aquifers, water tables, recharge, underground flow, and natural chemistry determine where this water accumulates and moves.
Some groundwater beneath the Sahara last touched the atmosphere before modern humans began farming. It entered the ground during wetter phases of the Pleistocene, moved slowly through sandstone, and remained isolated as the region changed into desert. This ancient reserve is called fossil water...
A flowing artesian bore appears to push water upward without a pump, but the force does not originate in a mysterious underground engine. It comes from hydraulic head. Rain enters permeable rock where an aquifer reaches higher ground, then moves beneath confining layers. At a lower elevation, a bore...
The Ogallala Aquifer does not decline at one uniform rate. In parts of the southern Great Plains, groundwater levels have fallen by more than 150 feet since widespread irrigation began. Elsewhere, especially beneath much of Nebraska, changes have been modest or water levels have risen during some...