Spatial distribution of oxygen-18 and deuterium in stream waters across the Japanese archipelago
- 1Center for the Promotion of Interdisciplinary Education and Research, Kyoto Univ., Kyoto University Higashi Ichijokan, 1 Yoshida Nakaadachi, Sakyo, Kyoto 606-8306, Japan
- 2Graduate School of Agriculture, Kyoto Univ., Kitashirakawa Oiwake, Sakyo, Kyoto 606-8502, Japan
- 3Field Science Education and Research Center, Kyoto Univ., Kitashirakawa Oiwake, Sakyo, Kyoto 606-8502, Japan
- 4DLD Inc., Ina, 2435 Kami Yamada, Takatoh, Ina, Nagano 396-0217, Japan
Abstract. The spatial distribution of oxygen and hydrogen isotopic composition (δ18O and δ2H) of stream waters across Japan was clarified with a data set by compiling sample data obtained from 1278 forest catchments during the summer of 2003. Both δ18O and δ2H values showed positive correlations with the mean annual air temperature and annual evapotranspiration, and negative correlations with latitude and elevation. Deuterium excess (d-excess) values in stream waters were higher on the Sea of Japan side, and lower on the Pacific Ocean side, of the Japanese archipelago. The d-excess in precipitation was generally higher in winter and lower in summer in Japan. The Sea of Japan side experiences a great deal of snowfall, and seasonal changes in monthly precipitation are rather small. In contrast, the Pacific Ocean side experiences a large amount of rainfall during summer with low levels of precipitation during the winter. Therefore, the lower d-excess in stream waters on the Pacific Ocean side reflects summer precipitation, and the higher values on the Sea of Japan side are affected by delayed recharge from snowmelt. The isoscapes of stream water connote not only spatially integrated but also temporally integrated isotope signals of precipitation and provide a framework for addressing applied hydrological, ecological, or meteorological research questions at regional scales, such as the effects of climate change.