Baseflow Distribution and Geomorphic Characteristics of Headwaters for Obtaining Distributed Domestic Water Sources During Natural Disasters

Abstract

　Stream water in headwater catchments is useful as a source of water for domestic use during long-term water outages caused by disasters in mountainous areas. Therefore, evaluating its availability characteristics and stream water quality as a water source is necessary for effective water use. We investigated 59 watersheds covered by Mesozoic sedimentary rock (27 ha average watershed area) on the edge of the Nobi Plain in western Gifu prefecture, Japan. Discharge of the streams was 17–9,361 m³/day. Discharge of springs was 2–432 m³/day. Headwater catchments with drainage area of ≥40 ha and relief height of ≥500 m tended to have high specific discharge with slight variation. Moreover, they exceeded the national average of ecological maintenance flow (0.73 mm/day or 8–2,574 m³/day). Water quality analysis and the stable isotope ratio suggest that catchments exceeding the ecological maintenance flow are stable water sources because of the dominant contribution of bedrock groundwater. Understanding hydrological processes in mountainous watersheds is useful not only to secure water for domestic use during disasters, but also as basic information for regional sustainable water resource management.