2021 Volume 103 Issue 2 Pages 145-155
Mountains are a source of water; thus information about water balance is important for water resources management. However, there is a lack of information, especially for high elevation areas, because it is often difficult to conduct measurement in high elevations. Here we report water balance at Kawamata catchment in the Chichibu Mountains (elevation 628-2,475 m, catchment area 94 km2) that consist of montane and subalpine forest. Because this catchment is relatively large, we need to consider spatial variation in precipitation. We tested the accuracy of 1 km mesh radar-raingauge analyzed precipitation, using measured point precipitation data within and near the Kawamata catchment and found that both monthly and annual precipitation measured by radar-raingauge and tipping bucket rain gauges showed almost 1:1 correspondence. We calculated water balance for years 2009-2018 using catchment mean annual precipitation obtained by 1 km mesh radar-raingauge analyzed precipitation and measured annual discharge. On average, annual precipitation, discharge and loss were 1,747±245 mm y－1, 1,375±220 mm y－1 and 372±78 mm y－1, respectively. This annual loss was considered equal to the annual evapotranspiration at Kawamata catchment. Our data and previous reports suggest that even in forested catchment in the same Kanto Region, annual evapotranspiration in a higher elevation catchment covered with montane and subalpine forest can be a few hundred millimeters smaller than that of forested catchment in a low mountain range and is also comparable to that of cool temperate and subalpine forests in the higher latitudes, such as Hokkaido and the Tohoku region.
