Study of stable isotopes for highly deformed aquifers in the Hsinchu-Miaoli area, Taiwan |
| |
| Authors: | Hsueh-Yu Lu Tsung-Ren Peng Tsung-Kwei Liu Chung-Ho Wang Chih-Chao Huang |
| |
| Institution: | (1) Department of Earth and Environmental Sciences, National Chung Cheng University, 168, University Road, Min-Hsiung Chia-yi, Taiwan;(2) Department of Soil and Environmental Sciences, National ChungHsing University, Taichung, Taiwan;(3) Department of Geosciences, National Taiwan University, Taipei, Taiwan;(4) Institute of Earth Sciences, Academia Sinica, Taipei, Taiwan;(5) Central Geological Survey, Ministry of Economic Affairs, Taipei, Taiwan |
| |
| Abstract: | This study was based on the analysis of isotopic compositions of hydrogen and oxygen in samples from precipitation, groundwater and stream water. In addition, parts of groundwater samples were dated by carbon-14 and tritium. These data are integrated to provide other views of the hydrologic cycle in the Hsinchu-Miaoli groundwater district. The groundwater district is principally composed of Pleistocene and Holocene aquifers. The Pleistocene aquifers are highly deformed by folding and faults into small sub-districts with areas of only tens of square kilometers. These aquifers are exclusively recharged by local precipitation. The Holocene aquifers cover narrow creek valleys, only tens of meters in thickness. The local meteoric water line (LMWL), constructed from rainfall samples in the Hsinchu Science Park, is described by the equation δD=8.02δ18O+10.16, which agrees with the global meteoric water line. In addition, the precipitation isotopic compositions can be categorized into two distinct end members: typhoon type and monsoon type. The groundwater isotopic compositions are perfectly located on an LMWL and can be considered a mixture of precipitations. Based on the mass balance of isotopic compositions of oxygen and hydrogen, infiltration is more active in the rainy season with depleted isotopic compositions. The amount of infiltration during May–September is roughly estimated to comprise at least 55% of the whole year’s recharge. The isotopic compositions of stream water are expressed by a regression equation: δD=7.61δ18O+9.62, which is similar to the LMWL. Although precipitation isotopic compositions are depleted during summer time, the isotopic compositions contrarily show an enriched trend in the upstream area. This is explained by the opposite altitude effect on isotopic compositions for typhoon-related precipitations. |
| |
| Keywords: | Stable isotopes Groundwater recharge Pleistocene aquifer Mid-northern Taiwan |
| 本文献已被 SpringerLink 等数据库收录！ |
|
