台中 - 南投地區為地下水儲存良好的地區，同時也是台灣各縣市中具備良好的地下水補注地區之一，然而，在此地區用來觀測地下水量的觀測井數量卻很有限，為了為研究區域提供充足的量測資料，我們採用了地電阻影像法(ERI)來進行地下水位高程的時序監測，並估算該地區的水文參數。本研究於2018年在研究區域內進行五次的地電阻時序施测，每次至少佈設11條测線，並採用Wenner及Schlumberger 陣列法進行施测。根據 Archie’s Law，首先由地電阻影像法所得到的結果估算地區的相對飽水度，接著計算 VG 水文參數，藉由土壤水特性曲線(SWCC)來驗證水頭高度，最後根據VG水文模型來估算比出水率(Sy)的理論值。研究結果顯示，區域的地下水位高程的變化介於22.85公尺及51.44公尺間，另外，二月份及其他施测月份的地下水位高程差值範圍介於1.64公尺至6.52公尺，最高的地下水位高程值出現在七月份(溼季)，而最低地下水位高程值則在二月份(乾季)，此外，研究結果顯示該區域的比出水率(Sy)約介於0.20至0.26，並在测線WS02量測到最低的比出水率(Sy)。;The Taichung-Nantou Region is the area with savings of the groundwater, and also with good recharge sources among the groundwater provinces in Taiwan. However, there are only limited observation wells for monitoring the groundwater quantity and quality in the region. In order to provide supplementary measurements for the area, we conducted Electrical Resistivity Imaging (ERI) surveys for time-lapse monitoring of the groundwater level, and also attempt to estimate the hydrogeological parameter. We deployed eleven ERI survey lines with both Wenner and Schlumberger array configurations and conducted the time-lapse measurements 5 times during the year of 2018. Based on the Archie’s Law, we first estimate the relative saturation with the ERI results, then calculate the VG parameters for identifying the water table using the Soil Water Characteristic Curve (SWCC). Lastly, we estimate the theoretical specific yield (Sy) based on the VG model. Our results show that the groundwater level varies between 22.85-m to 51.44-m in the area. In addition, the difference of groundwater level against that measured ones in February is ranging from 1.64-m to 6.52-m. The highest groundwater level took place in July (the wet season) and the lowest groundwater level appears to be in February (the dry season). Moreover, we found that the Sy values are about 0.20-0.26 in the study area, and the lowest Sy value is in the WS02 line.
