Genetical relationship of ground water and river water to precipitation suggested from several observation results of their hydrogen and oxygen isotopic ratios at Akita

Abstract

Hydrogen and oxygen isotopic ratios of ground water and river water are compared with those of precipitation at Akita, and genetical relationship is discussed among these three waters. The isotopic ratios of ground water and river water are fairly constant through a year, and similar to those of annual mean precipitation. This suggests that a part of precipitation flowing out to river is not subjected to modification of isotopic ratios by evaporation, evapo-transpiration, direct runoff and others which happen near ground surface. If this is the case, some possible processes are required, for example, the part flowing out to river penetrates separately from the part subjected to the above isotopic modification, or precipitation penetrating mixes well and such homogenized water is returned to atmosphere.Or, it may be necessary to consider any other possible processes.