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

Abstract

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.