Flow analysis of groundwater with seasonal variation of temperature, electric conductivity, and oxygen isotope for heat utilization in Sho River alluvial fan, Toyama, Japan

Seasonal variation of water temperature, electric conductivity, and oxygen isotope composition was determined in the Sho River alluvial fan, western Toyama Prefecture, to examine groundwater heat utilization for indoor climate control. Samples were collected at 31 sites every 2 months for 1 year and at 11 representative sites monthly. The groundwater sources are a mixture of river water and precipitation. The contribution of precipitation to groundwater is generally small along the Sho River but reaches as much as 80% along the Oyabe River and in the south and west of the alluvial fan. Though the origin of the groundwater differs regionally, water temperature is fixed at about 15°C throughout the year in the northern part of the alluvial fan, and open ground source heat pump systems can be used for cooling and heating there.