The hydrologic response to development of three of the most heavily pumped sedimentary aquifer systems in the United States is similar in some aspects and different in others. In the semiarid West, an unconfined sand aquifer and a confined sand and clay aquifer system have been subjected to withdrawals that are far greater than predevelopment recharge rates. As a result, the aquifers have large losses of ground water from storage. In the humid East, pumpage from a carbonate aquifer system has resulted in induced recharge and diversion of natural discharge with insignificant loss from storage. However, the following responses to development are common in all three aquifer systems: (1) ground-water circulation has increased,

(2) rates of recharge have increased—mostly due to recirculation of pumped ground water, or infiltration of imported surface water used for irrigation in the semiarid West,

(3) locations of recharge areas have changed, and (4) natural discharge has decreased.

Regional water-level declines associated with ground- water development are inevitably accompanied by some combination of elastic compaction of aquifer material, inelastic compaction of fine-grained sediments and land subsidence, dewatering of aquifer material near pumping centers, and induced formation of sinkholes. The degree to which these changes occur is dependent on: (1) rates of pumping in relation to available recharge, and (2) lithology, specifically the proportion of sand, gravel, silt, clay, and carbonate rock that comprise the aquifer system.