高頻地下水位監測系統之設置與地下水位分析

High Frequency Monitoring System of Groundwater Level and Data Analysis

李佳慧(Chia-Hui Lee)

指導教授 ： 賈儀平

國立臺灣大學/理學院/地質科學研究所/碩士(2013年)

https://doi.org/10.6342/NTU.2013.00696

摘要

台灣的地下水位觀測井遍佈沖積平原與盆地地區，水位記錄通常以時水位為主，少部分監測頻率為分鐘或秒鐘等級。在地下水位記錄中，有時可見不同於降雨、潮汐、氣壓、或地震等自然因素引發的異常地下水位變化，將之與人為活動(例如抽水或停抽)進行對比後，亦無明顯證據顯示此類異常變化與上述因素相關。追蹤異常變化的可能原因後，發現主要與監測系統的設置或運作有關，而且資料錯誤或缺漏呈現多元的型態，容易影響分析結果。本研究嘗試建立一個採用沉水式壓力轉換儀作為核心的高解析度的高頻遠端地下水位監測系統，因此亟需探討地下水位監測系統中，造成記錄錯誤的來源。本研究發現影響水位記錄解析度、穩定度等因素存在於監測系統中的各項環節，例如不當選用沉水式壓力轉換儀的最大承載壓力限度，或者資料記錄器未使用合宜的資料處理模式進行設定等，同時溫度與電壓穩定性亦會影響監測結果，降低水位記錄的正確性，此外監測系統內部的相關搭配元件設置，也會影響地下水位的記錄。於排除監測系統內各種可能影響記錄品質之因素後，本研究將高解析度的高頻地下水位監測系統設置在南投縣社寮國小的地下水位觀測井，以1Hz的頻率監測地下水位，解析度為0.2公釐，發現社寮的地下水位會對降雨產生即時反應，出現微幅的動態變化，顯示社寮含水層會對降雨引發的地表荷重變化產生反應，含水層因地表荷重改變而產生極為小幅的體積膨脹與壓縮，引發地下水位變化。同時，藉由提升地下水位監測系統的解析度與記錄頻率，監測系統對同震反應的靈敏性亦提升，可以監測地震對自由含水層的地下水位影響，並從而建立一個高解析度的高頻地下水位監測系統所需的背景條件概念。

關鍵字

地下水位 ； 降雨 ； 荷重作用 ； 監測

並列摘要

Groundwater level monitoring wells are densely distributed in the plains and basins of Taiwan. The groundwater level is usually recorded every hour at these wells; only a few wells recorded every minute or every second. After analyzing groundwater level data, we found some abnormal groundwater level changes inconsistent with those induced by natural factors or human activities. These erroneous records may mislead the results of hydrologic analysis or research. This study intends to develope a remote high resolution and high frequency groundwater level monitoring system. It is essential to identify the source of error in the component of the system. It was found that inappropriate setting and installation would cause incorrect groundwater level record, such as exceeding the full scale pressure of the submersible pressure transducer or improper for data processing. The stability of the monitoring environment is also important, such as the consistency of voltage or variation of temperature. After factors might interfere data recording were reduced as possible, the groundwater level monitoring system was installed in Shelia. The recorded groundwater level data indicated that the auqifer is mostly unconfined. And it was found that groundwater level changed in a fluctuation pattern as rainfall occured, which indicated the loading to aquifer changed due to precipitation and resulted in the compaction and dilation of the aquifer. As promoting the resolution and accuracy of groundwater level monitoring system, the sensitivity to response earthquake rose as well, and a foundamental requirment to a high resolution and high frequency groundwater level monitoring system was also enhanced.

並列關鍵字

groundwater level ； monitoring ； rainfall ； loading

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