Abstract
Seasonal variations of water temperature, electric conductivity, and oxygen isotope and chemical composition of shallow groundwaters and river waters were determined in the Sho River alluvial fan, western Toyama Prefecture, Japan, 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. In addition, the results of monthly precipitation amount and oxygen isotope composition of precipitation collected within the region during the same period were also taken into account. The sources of the shallow groundwaters 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 around 15 °C throughout the year in the northern part of the alluvial fan, and open-type ground source heat pump systems can be used for cooling and heating there, if adequate quantitative aquifer properties (exploitable groundwater amounts) are present.
Highlights
In Toyama Prefecture, Japan, a large amount of groundwater flows from the mountains (~3000 m in altitude) to the Sea of Japan within 100 km [1]
Because the water temperature of shallow groundwater in Toyama is approximately 15 ◦C throughout the year (Toyama Prefecture, 2006), groundwater can be used as a heat source for indoor climate control of houses and industry, using the temperature difference between air and groundwater
There are previous reports on the state of recharge and groundwater flow in the Sho River alluvial fan based on stable isotope and chemical components [5,27,28]
Summary
In Toyama Prefecture, Japan, a large amount (more than 150 million tons/year) of groundwater flows from the mountains (~3000 m in altitude) to the Sea of Japan within 100 km [1]. There are previous reports on the state of recharge and groundwater flow in the Sho River alluvial fan based on stable isotope and chemical components [5,27,28]. Iwatake et al [15] analyzed the chemical composition of groundwater collected in August 2011 and showed that groundwater is enriched in Ca2+ and HCO3− by dissolution of carbonate rocks They evaluated this area for the applicability of GSHP and the degree of scale creation by chemical components such as iron and calcium carbonate. The aim of this study is to examine annual seasonal variations of groundwater flow patterns in the Sho River alluvial fan and to select suitable areas for open-type GSHP for industrial and domestic use.
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