STUDY ON GRADUAL DECREASE IN GROUNDWATER LEVELS OVER THE KUROBE ALLUVIAL FAN

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To understand the characteristics and seasonal changes in flowing artesian wells in the Kurobe River alluvial fan (KRAF), the discharge, water quality, and isotope ratio of 23 flowing wells were observed for 18 months from March 2011. This paper newly reports the monthly discharge and water quality of these flowing wells. Variation in water flow at 10-minute intervals is also presented. All wells exhibited the same seasonal changes, and no spatial difference in water quality was found. Analysis of isotope ratios indicated that three wells located on the left bank of the KRAF were recharged from difference sources than the other wells that were recharged by the Kurobe River. Comparison with previous water quality measurements taken 10 to 20 years ago showed that the water quality had not changed. However, further research is needed to clarify long-term trends of the flowing water discharges.