WATER BALANCE ANALYSIS CONSIDERING RUNOFF OF UNGAUGED CATCHMENTS IN IWAKI RIVER BASIN, NORTHERN JAPAN

For integrated and sustainable water resource management, it is essential to understand water balance of river basin. Infiltration calculated by subtracting evapotranspiration and runoff from precipitation is a key factor for groundwater resource development and is an important input data for three-dimensional groundwater flow analysis. For estimation of runoff, it needs a great challenge to establish a method for runoff in ungauged catchments, because gauging stations are usually set up in the limited main rivers. This paper focused on close relation between topography and runoff. Then, the runoff of ungauged catchments in the Iwaki River Basin was estimated by "runoff index" derived from results of geomorphometry and multivariate statistics using digital elevation model data. Comparisons between runoff indices and measured runoff data, showed clear positive correlations. This result proved that runoff index was useful for runoff estimation, and suggested that it was possible to estimate runoff of ungauged catchments from runoff index by linear regression equation.