The use of the stable isotopes to determine the pattern and spatial extent of groundwater flow in the Tatun Volcano Group(TVG), Taiwan

Abstract:

Over 200 water samples including rain water, surface water and groundwater from August 2012 to June 2013 in the Tatun volcano group were collected and analyzed. The groundwater levels and precipitation were integrated with oxygen and hydrogen isotope data to understand the mechanism of groundwater recharge. The results show that the isotope composition of surface water are enriched in winter (δ18O=-6.03 ‰, δD= -27.27‰) and depleted in summer (δ18O= -6.12‰,δD=-29.25‰), indicate that the water mass comes from different sources in summer and winter. The seasonal variations of hydrogen and oxygen isotope composition of groundwaters (δ18O=-5.9 ‰, δD= -28.4‰) are significant different from that of surface water. This indicates that it takes a significant period of time to have the rain water mixed with groundwater. The main recharge season of groundwater in the northern Cising Mountain is winter while summer is the main recharge season of groundwater in the south of the mountain. Therefore the isotope composition of groundwater in northern watershed are generally more enriched than that of the southern watershed.