Spring Water
Minami Aso is located between the central volcanic cone group and the outer rim of the Aso Caldera. An abundance of natural springs is found in this area. Rainwater in Aso flows through the central volcanic cone and southern outer rim, draining into the lower basin of the mountains through permeable volcanic rock strata.
Within the lower basin, groundwater collects in natural underground reservoirs, which in turn feed streams and rivers that irrigate northern Kyushu. These subterranean reservoirs are the main source for the six main rivers that provide over five million people with water for living and agriculture.
In certain areas, groundwater wells up under cliffs and at the base of hills, forming natural springs, rivers, and wetland areas characterized by fresh, clean water. One complete cycle, from water falling as rain to reappearing in a freshwater environment, takes between twenty and thirty years.
Volcanic activity in the Aso area has resulted in the formation of various geological structures in Minami Aso. The excellent quality of water associated with the natural springs in the area is the result of groundwater from these underground sources having been filtered through tunnels and rock layers before reaching individual springs. Water from these springs has sustained life and human activity for thousands of years.