ABSTRACT
This chapter explains the fundamental aspects of subsurface water. Subsurface water flows below the ground surface. Most aquifers are underground storage reservoirs made up of water-bearing permeable rock or unconsolidated materials. Water penetrates downward through the pores by gravitational forces until it reaches the saturated area. Aquitards are zones within the earth that limit the groundwater flow from one aquifer to another. They are beds of low permeability along an aquifer. Changes in groundwater storage due to pumping and recharge result in changes in the water table and the piezometric surface elevations. Allogenic recharge occurs when the adjacent nonkarst areas recharge the karst aquifer. There are different classifications of karst according to its morphological features, structural factors, geographical position, and depositional environment of carbonate rocks. Karstification occurs by the chemical, and sometimes mechanical, action of water in a region of limestone, dolomite, or gypsum bedrock.
