Abukuma Cave located in the southern part of Fukushima Pref. (about 180 km from Tokyo to the north), is a famous huge karst cave. Also, Irimizu Cave is located in the north of the karst area and well known as a cavern. These caves form a large cave system (just like a drainage system in the karst area). There are many karst caves in Japan and they have become tourist spots with various sightseeing plans. However, many unknown things remain from the viewpoint of hydrological sciences. This study tried to make clear the environment and drainage system of the karst cave system.
