Pumping too much water from an aquifer causes the water level to decline or the pressure to drop. Groundwater offers some tremendous advantages over surface water. Naturally filtered as it makes its way through layers of soil, groundwater is generally free of bacteria and sediments. Groundwater is less affected by rainfall variations, and therefore a more dependable source during low rainfall years than surface water. Treatment and distribution costs are minimal compared to surface water because groundwater is usually high in quality and near to the demand site.
Some aquifers can hold water for centuries without losing water to evaporation or seepage.
Aquifers are also more protected from pollutants than are surface sources. Wells and pumps have much less impact on an environment than dams, reservoirs, canals, and other surface water development facilities.