| dc.description.abstract | Average annual precipitation is about 2500 millimeters in Taiwan. It varied with difference in season, location and elevation. Water storage is especially difficult in steep terrain areas. In order to promote effective application and avoid depletion of groundwater resources, rational evaluation and management of groundwater are needed in achieving accurate and reasonable estimation of groundwater resources. In this study, water samples were collected monthly from June 2010 to May 2011 in Jianshih well field and nearby areas. Surface water samples were taken from gullies and rivers, groundwater samples were taken from wells. hydrogen and oxygen stable isotopes as well as major cations and anions were analyzed, so as to evaluate their temporal and spatial variations in geochemical characteristics. Furthermore, integration of geographic information systems plus previous studies of groundwater flow from 2008 to 2011 in Jianshih area, the controlling factors of groundwater hydrology and geochemical characteristics can also be examined. The results show that the isotopes of groundwater are heavier in the low-ppt season. Additionally, surface water are evenly distributed near MWL both in hi-ppt and low-ppt season, which implied the source of recharge was not subjected to differentiation and evaporation; Besides the influence of precipitation, no significant change in water table can be observed. According to hydrochemical data, most of the groundwater in the well field exhibit weak alkaline whereas Well W-2 shifted to type III (alkaline-earth, non-bicarbonate) in October and November of 2010, probably due to the release of alkaline-earth metals and sulfate after a long residence time of groundwater. Finally, recharge source of groundwater was calculated by the mass balance from oxygen and hydrogen isotopes. In conclude, gully water and river water are the main sources contributed into the well field both in high and low precipitation seasons. The contribution of river water is especially noticeable at well W-1 during low-ppt season.
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