Hydrogen and Oxygen isotopic ratios of river water in the Kanto Plain and surrounding mountainous regions, Japan

Abstract

To provide a quantitative background for evaluation of a complex interaction between surface and groundwater in the Kanto Plain, spatial and temporal distributions of oxygen and hydrogen isotopic ratios of river waters in the Kanto Plain and surrounding mountainous regions were investigated. Temporal variations of δD values for river waters sampled at the points where mountain rivers flow into the Kanto Plain were small comparison of spatial variations. The hydrogen isotopic ratios of river waters tend to have lower values for the upstream of Tone river basin, and higher values for the eastern part of the Kanto Plain. The hydrogen isotopic altitude effects of river waters were calculated at -2.4‰ δD/100m. Although each river basin has similar values of the isotopic altitude effects, δD values of the Ara and Tone river basin were 5-10‰ smaller than the Naka and Kuji, Kinu and Kokai and Watarase river basin at the same altitude.