Abstract
Studied regionChokai volcano is composed of low-permeability andesite lava, a snowfall-influenced hydrological setting that has been little studied. Study focusSnowfall there is expected to decrease due to climate change and expanded quarrying along its southern foot. To evaluate the effects of future environmental changes on the groundwater discharged from springs at the feet of lava flows, which is used for agriculture and domestic purposes, we used isotopic, hadrochemical, geologic, meteorological, and topographic information to elucidate the recharge area, major recharge season, and underground flow of spring waters and surface waters at Chokai. New hydrogeological insights for the regionGroundwater and surface water are of NaCl type with high deuterium excess values, indicating a strong contribution of atmospheric deposition of sea salt aerosols during winter. Altitude indicators based on water H and O isotopic compositions and chloride ion concentrations suggest that the foothill springs are recharged mainly on gentle slopes below ∼700 m elevation. This area is generally covered with volcanic sediments, which contain wetlands and perched aquifers that continuously supply groundwater to the underlying lava through fractures and voids without thorough mixing in the lava aquifer. Anticipated decreases in snowfall and the removal of surface rocks may adversely affect not only the foothill springs supplied by snowmelt and the rice cultivation that depends on them, but also the wetland ecosystem.
Published Version
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