扇状地浅層地下水の水素および酸素同位体比;扇状地浅層地下水の水素および酸素同位体比;Hydrogen and Oxygen Isotope Ratios of Groundwaters in Shallow Aquifers beneath the Alluvial Fan

Hydrogen and oxygen isotope measurements of river waters, spring waters of rainfall infiltration origin, and rice paddy waters collected in Toyama Prefecture have been used to deduce a mixing model for identifying sources of groundwater in the shallow aquifer beneath the alluvial fan. 6 D and 6 180 values of the river water flowing on the fan depend on the average altitude of its catchment area. Their variations are limited throughout the year. The spring water from Kureha Hill can be regarded as a representative of rainfall infiltration, of which D and 6 180 values are -49.3 and -8.8%0 in average, respectively. The rice paddy water irrigated by the main river flowing on the fan shows isotopic fractionations of A D =12.3%0 and A180=2.6%0 in average, caused by evaporation at its surface. A model based on intermixing of such source waters has been proposed to identify 本研究の大部分は1998年秋季講演会にて発表 富山大学理学部生物圏環境科学科 Department of Environmental Biology and Chemistry, Faculty of Science, Toyama University (1998 3 ri igis) 富山大学理学部生物圏環境科学科 Department of Environmental Biology and Chemistry Faculty of Science, Toyama University 富山大学理学部地球科学科 Department of Earth Sciences, Faculty of Science, Toyama University (Wf IL ill Vi **-/±) 富山大学理学部生物圏環境科学科 Department of Environmental Biology and Chemistry, Faculty of Science, Toyama University (現在 海道工業株式会社) 同上ditto(現 在 群馬県警察) "同 上ditto(現 在 別府市水道局) sources of groundwater in shallow aquifers beneath alluvial fans in Toyama Prefecture . Application of the model to groundwaters of Shogawa and Kurobegawa Fans has confirmed its validity.