| Summary: | 碩士 === 國立臺灣海洋大學 === 河海工程學系 === 107 === Groundwater monitoring data reveal response of hydrological cycle, rainfall-recharge processes, and hydrogeologic characteristics of groundwater aquifers. Prior to quantitatively estimating groundwater recharge, groundwater recession behavior and correlations between recession rates varying with depths and aquifer hydraulic properties must be understood. This is beneficial to developing a more realistic estimation model for groundwater recharge, which is particularly important in study areas where recharge occurs in the formation of mountainous areas. Since groundwater recharge to regolith-fractured rock aquifers dominates by lithology and fracture properties, this may affect the duration and amount of recharge. Thus, this study is to develop groundwater recharge estimation techniques within regolith and fractured rock formations. The main point of this research is to conduct correlation studies between fractured rock properties and recession rates. Meanwhile, the above study outcome incorporated into two rock mass permeability index systems is capable of developing empirical models for estimating recession rates which can help speed up groundwater recharge calculation and obtain actual recession behaviors in response to intrinsic properties of regolith-fractured rock aquifers.
This study collected groundwater monitoring data from 20 wells located in the mountain basin in central Taiwan. The maximum monitoring data applied here lasts for eight years; the least period is three years. Based on these groundwater data, the groundwater recharge estimation model for each well has been developed. Besides, this study confirmed that geological conditions varied with depths controlled recession rates. Subsequently, the rock mass permeability index systems (HPF) that can quantitatively estimate hydraulic properties for recession periods were proposed. Meanwhile, the study obtained an empirical model of recession rate versus permeability index with a high correlation for each well. This outcome can meet the objective of helping ease groundwater recharge calculation. Finally, a comparison between the proposed method and the traditional method, which used the recession rate occurred in the dry season as a representative recession rate, has been conducted. The result indicated the traditional approach underestimated groundwater recharge amount because the typical recession rate is not applicable to actual recession behaviors occurred in the wet season. In particular, computational differences frequently appear in complex geological environments.
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