A Thousand Years of Rain and Grasslands to Enrich Aso: A Water Civilization Born of Volcanoes

A Thousand Years of Rain and Grasslands to Enrich Aso: A Water Civilization Born of Volcanoes

The Aso area has a high rainfall of up to 3,000 mm per year and has played an important role as a water source for major rivers in Kyushu, such as the Chikugo River, the Shirakawa River, and the Midorigawa River. The huge caldera topography functions as a natural dam that receives precipitation, allows it to percolate into the earth, and then sends it out as spring water and rivers. Research has shown that the vast grasslands of Aso also play a key role in the water cycle, and the porous grassland soil has the same groundwater recharge capacity as forests. The grasslands have been kept young by field burning, and the network of roots has continued to act like a sponge that stores water. This water cycle, which is the result of cooperation between nature and man, supported the formation of villages and paddy rice cultivation from the medieval to early modern periods, and records of spring water management and waterways remain in ancient documents. The maintenance of grasslands
was also linked to pastureland management and was essential for farming and raising cattle and horses. Since the modern era, the value of the area as a water source has been further recognized, and today the relationship between grasslands and water is being reevaluated as a cultural landscape. Aso's rich water environment can be said to be a water civilization built through the layered activities of volcanic landforms and grasslands.