Abstract
In the downstream area of the Echi-gawa river, groundwater is dominantly utilized for industrial water and irrigation in the Shiga Prefecture. The Echi-gawa alluvial fan is the main recharge area of the groundwater along the Echi-gawa river. To understand the groundwater flow system in this area, the relation between water temperature and groundwater flow is investigated with shallow and deep wells.
The shallow groundwater temperature of constant temperature layer has a difference of approx.0.8°C with 15.5°C in right bank, 16.3°C in left bank of the river. Vertical direction of groundwater flow was belting in the apex alluvial fan and fluvial terraceII. The deep groundwater temperature indicated that was 15.0∼15.5°C in the entire basin of right bank and rose in temperature along the depth in the left bank as surface layer is 16.0°C, middle layer is 16.5°C, deep layer is 17.5°C.
The estimated horizontal velocity of groundwater was that right bank is 4×10-3cms-1, left bank is 3×10-3cms-1 in the shallow layer and left bank is 7.4×10-5cms-1 in the deep layer. Furthermore, at the center of fan in the left bank, calculated vertical velocity of the deep layer is 2.4×10-7cms-1 in April, 8×10-7cms-1 in June.
