Stable isotope studies of precipitation and river water in the Lake Biwa basin, Japan

Abstract

Abstract:The d 18O and dD in 17 river waters¯owing into and out of Lake Biwa, the lake water itself and precipitation at 11 locations in the Lake Biwa basin were observed from October 1996 to September 1997, to evaluate the origin of river waters and the eect of irrigation water from the lake on the river waters¯owing into Lake Biwa. The regional dierence and altitude eect of the stable isotopes in precipitation and river water were found in the basin. The d 18 O in the rivers which are located in the eastern and the southern areas in the basin is heavier than that of the other rivers, due to the eect of irrigation for the nearby paddy ®elds. Evaporation from Lake Biwa and the in¯ow rate into the lake estimated from the d 18 O balance agree well with the results of previous studies which used water balance methods. The stable isotopes can enable us to evaluate not only water balance but also the origin of the water and the water¯ow system.

The contemporary stable isotope hydrology of Lake Suigetsu and surrounding catchment (Japan) and its implications for sediment-derived palaeoclimate records

“…However, our findings were consistent with others from central Japan (e.g., Taniguchi et al, 2000), which note that for contemporary isotopes there is no significant difference in δ 18 O and δ 2 H between EAWM and EASM precipitation. As such, it is important to note that unlike Continental Asia, annually integrated δ 18 O and δ 2 H do not reflect the changing relative input of EAWM and EASM precipitation, because their compositions are so alike.…”

“…These trajectories, which ultimately reflect the operation of the EAM as dual EAWM and EASM modes, highlight the influence of the EAM on the climate of Japan, and can explain the lack of distinctive seasonal precipitation δ 18 O and δ 2 H trends at Wakasa. EAWM and EASM precipitation over Japan generally have very similar compositions (Taniguchi et al, 2000;Uemura et al, 2012) et al, 1998). EAWM air masses originate in central Asia and Siberia and are predominately cold and dry, and hence whilst distillation and moisture recycling earlier in the trajectory is possible, the isotope signal of EAWM precipitation over Japan is dominated by the interaction of this air mass with the Sea of Japan.…”

Estimation of the Isotopic Composition and Origins of Winter Precipitation Over Japan Using a Regional Isotope Circulation Model

“…Waseda and Nakai () explained the seasonal variation in d‐excess of precipitation over Japan. Since their study, the dominant source of winter precipitation has been assumed to be the Sea of Japan when the d‐excess value of winter precipitation is >20‰ or higher than the average value in summer (e.g., Kabeya et al, ; Katsuyama et al, ; Nakayama et al, ; Taniguchi et al, ; Yabusaki, ). Our study finds that the d‐excess value of precipitation in both the WM (>20.0‰) and EC (~12.0‰) types was higher than that of summer precipitation (>4.0‰, Figures a and b) over Japan.…”

Flow path depth is the main controller of mean base flow transit times in a mountainous catchment

“…We calculated the deuterium excess (d‐excess), which is the surplus of deuterium relative to the relationship between δ 18 O and δD [ Dansgaard , 1964], assuming an equilibrium condition with a slope of 8, which is the slope of global meteoric water line and average of river, lake, rainfall, and snow in many parts of the world [ Craig , 1961b]. The d‐excess in precipitation showed a clear sinusoidal seasonal pattern around the study area [ Taniguchi et al , 2000], and this seasonal pattern has been useful in evaluating MTT in this region [e.g., Kabeya et al , 2007].…”