| Summary: | 碩士 === 臺灣大學 === 生物環境系統工程學研究所 === 98 === The groundwater resource is abundant in Taiwan and it is making a critical issue to exploit groundwater resource properly. Groundwater resources could be well managed and utilized if the storage and movement of groundwater is rationally evaluated. The continually declining groundwater level in Chou-shui river alluvial fan is mainly caused by the unregistered pumping by private wells due to enormous water demand from agriculture and aquaculture, in turn leading to land subsidence and soil salination. In addition, the construction of Taiwan High Speed Rail (THRS) has caused serious land subsidence in Tuku and Yuan-Chang township. This research estimated ground water storage, recharge, and withdraw rate in Chou-Shui river alluvial fan by developing numerical model with MODFLOW and SWAT. Unregistered withdraw by private wells in this area are investigated through comparing registered groundwater rights from Water Resources Agency with simulated discharge. Finally, the recharge efficiency of artificial lakes with radii of 3 km and 1.5 km along the THRS were addressed. Results show that, during 1999 to 2002, averaged recharge in the Chou-Shui river alluvial fan is 1.24 billion tons/year, side-stream recharge is 895.7 million tons/year, and unregistered pumping from private wells is 1.1941 billion tons/year. Scenarios with different elevation, soil, and land use type lead to diverse recharge rate. Highest recharge rate is found at the proximal fan, which is 1 million tons/year/km2. Moreover, recharge rate is 940 thousand tons/year/km2 at Gu-Keng and Dou-Liu, and 532 thousand tons/year/km2 near the Pei-Kang river, the worst case. The locations of two THSR recharge scenarios are close, result in similar recharge rates, which are 807.8 thousand tons/year/km2 for the 3 km lake and 797.2 thousand tons/year/km2 for the 1.5 km lake.
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