Discussion on Groundwater Conservation Strategy for Land Subsidence：Area along the Yunlin High-Speed Rail

Abstract

Yunlin County is currently a region with a serious subsidence in Taiwan Subsidence trend has gradually shifted from the early coastal areas to inland even jeopardizing the safety of high-speed rail From the past research results it is known that over-pumping groundwater is the main cause of land subsidence The over-pumping of groundwater in inland areas is also related to the increase of water demand for various targets Relevant units have successively proposed measures for prevention and control of subsidence The study focused on the three-kilometer gold corridor area along the high-speed rail simulating the recharge of groundwater without affecting normal water supply and assessing the effectiveness of slowing down the land subsidence In this study the regional water resources application simulation model (WRASIM) combined with the groundwater flow numerical simulation model (MODFLOW) was used to simulate water resources utilization of the Zuoshui River Basin and add the recharge facility such as: Infiltration Basins; Aquifer Storage and Recovery well Measures to assess the effect of increasing the groundwater level in the gold corridor area when filling groundwater at different locations Under the groundwater level simulation results of the above model this study uses the SUB module of MODFLOW model to simulate subsidence of the gold corridor area The initial values of the model parameters are set with reference to the previous research results and then the specific parameters are sensitive and verified The results show that the amount of subsidence is between 0 31% and 8 86% Finally two groundwater recharge measures were developed and simulated to improve the formation subsidence in the gold corridor area There are three options for evaluation Option 0: No increase in pumping and replenishment scenarios; Option 1: Use the channel on the south bank of the Zhuoshui River to draw the remaining flow of the collection to the top of the artificial Infiltration Basins; Option 2: On the basis of the option 1 use the Hushan Reservoir The excess water storage is delivered to the Aquifer Storage and Recovery well in the severely trapped area It can be found from the simulation results that the improvement of the groundwater level in the adjacent recharge lake area is obvious and the increase in the farther areas is less In the second case the overall water level is significantly improved In the simulation of subsidence although the option 1 has unevenly promoted the groundwater level in the study area it still improve the subsidence The option 2 has a significant effect on the overall subsidence improvement The results show that both recharge schemes can improve the subsidence while the improvement effect of scheme 2 is better

Date of Award	2019
Original language	English
Supervisor	Nai-Fang Chou (Supervisor)