Study on temperature change in subsurface variable temperature zone for direct geothermal heat utilization in Aizu Basin

2019 Fiscal Year Final Research Report

• Project/Area Number: 16K00646
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Design and evaluation of sustainable and environmental conscious system
• Research Institution: Fukushima University
• Principal Investigator: SHIBASAKI Naoaki 福島大学, 共生システム理工学類, 教授 (70400588)
• Project Period (FY): 2016-04-01 – 2020-03-31
• Keywords: 地下水温 / 地中温度 / 地下変温層 / 地下水位 / 地下水流動

Outline of Final Research Achievements

The study was conducted at paddy-field areas in northern Aizu Basin to reveal the relationship between changes in ground temperature in variable temperature zone and effect of groundwater recharge, and to obtain basic data for management of ground temperature for efficient use of shallow geothermal heat. Groundwater temperature, ground temperature in variable temperature zone and groundwater level were measured in the study. The fluctuation range and pattern of ground temperature change were different by location, indicating heterogeneity of gravel layer and variable thickness of the cultivated soil layer at the paddy field may influence the temperature. It was also confirmed that the effect of groundwater recharge on the ground temperature was hardly observed in the saturated zone, but significantly observed in the unsaturated zone. The study area, located on an alluvial fan, may be a suitable site for direct geothermal heat utilization system that utilizes advection of groundwater.

Free Research Field

水文地質学

Academic Significance and Societal Importance of the Research Achievements

福島県喜多方市では，「冬水田んぼ」による地下水の人工涵養実験が行われてきた。冬季に低温の水を涵養させると地中温度が低下する可能性が指摘され，それが再生可能エネルギーとしての地中熱利用にとって，利用効率の低下につながることが懸念された。本研究の結果，本研究地において，涵養水による温度変化は，飽和帯ではほとんど影響を受けないことが明らかになった。また，扇状地に位置する本研究地は地下水の移流を活用した地中熱利用システムの適地であることが明らかになった。