Determination of Runoff Components Using by the δ18O Tracer

Abstract

The storm hydrograph was separated into “old” and “new” water components using oxygen isotopes (δ18O) of water during a storm event which total rainfall was 4 mm. In the two small forested basins which discharge areas are 53.4ha and 1.6ha, principal component analysis, determination of runoff components and quantitative analyses were calculated. The hydrograph in small basin showed large variations related to the precipitation, but that in large basin showed slowly increase and decrease. Time series of the stormflow agreed well with the change of δ18O compositions in both basins. The results of determination of runoff components indicated that the new water component contributed to the differences of runoff characteristics in two basins. The proportions of new water to total precipitation was 3.4% in large basin and 1.5% in small basin, respectively.