| Summary: | 碩士 === 國立成功大學 === 資源工程學系碩博士班 === 96 === Most all rivers in Taiwan are short and steep and precipitation is unevenly distributed spatially and temporally. It leads to that the topic of riverbank storage near the stream become an important issue, especially in the area for the lack of storage facility. The riverbank as stream infiltration recharging groundwater can be explored the groundwater sources to decrease the rate of groundwater level and to increase the efficiency of water sources supply.
The purposes are to study the effect of pumping water on the riverbank with variable horizontal wells in order to expand the pumping water area, decrease the groundwater drawdown, and increase the yield volume of groundwater. Several procedures are provided. First of all, the hydrogeological model was bulit and then the numerical model of groundwater was performed by MODFLOW. Second, the analytical solution of Joshi (1988) and Lv-jing (1993) were compared with the results of numerical model to increase the reliability of this model. The different conditions were simulated to assess the efficiency of horizontal well setting. Finally, the water budget analysis was used to estimate the sources and the volume of permeated water. It was also discussed with horizontal well in different pumping settings in Zhutang and Lin-Bian Rivers.
The results indicated that the amount of pumping under the restrainted conditions of limited drawdown and serious limited drawdown were l7,404 and 14,104 cmd, respectively in Zhutang River. The case of limited drawdown could avoid more serious drawdown for single well and more suitable for the riverbank. On the other hand, the affective radial was insignificancy and the recharge from river to the aquifer was efficiency in the case of serious limited drawdown while it was suitable to temporary drought states. The simulation in Lin-Bian River indicated when the depth of gallery was increased 10m and 20m, the yield volume increased 32,889 and 35,926 cmd, respectively. Moreover, when the depth of gallery was increased 10m and 20m, the river leakage was also to increase 31,840 and 34,834 cmd, respectively. From results of yield and leakage, the increased depth of gallery can be to cause recharge more efficiently.
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