Springs have long been the source of water for mountain inhabitants where cultures developed around terrace agriculture that sustained civilizations such as the Incas in the Andes Mountains of South America (Figure 40), who engineered structures around mountain springs and canals to carry the water through the terraced agricultural area and into the city to fountains where residents could obtain water.
Approximately 12% of the world population lives in mountainous areas today and, to a large extent, depends on groundwater as their source of water. Most mountains exhibit steep terrain and are comprised of fractured rocks with minimal capacity for storing water. Consequently, groundwater typically circulates rapidly, often discharging to springs on the mountain slopes where the water table intersects the ground surface or to mountain streams. Forested mountains have soil formed from the forest ecosystem that prevents rapid storm runoff, thus promoting groundwater recharge and water storage in the groundwater zone with slow release to streams. Deforestation reverses this and promotes drying mountainous terrain and less availability of water to support stream flow and ecology. Although mountain hydrology is important to more than a billion people in the global population, it is not well studied because of difficulties associated with drilling wells in mountainous terrain.