運用新型熱傳輸模式與地下溫度剖面推估降雨入滲率

降雨入滲為地下水的重要補注來源，但直接量測入滲率在實際執行上有所困難。例如以傳統雙環入滲計無法量測完整的入滲過程，而以土壤水分計或張壓力計等方法在安裝儀器時需要相對專業的訓練與較高的成本。由於地下水與土壤之間存在持續的熱交換，進而影響地層中的溫度剖面（簡稱地溫剖面），故近年來已有研究利用熱作為示蹤劑觀測地面水與地下水之間的互動。因此，本研究以新興的分散式光纖測溫系統量測地溫剖面，並發展新的熱傳輸解析模式，結合最佳化方法來推估現地入滲率。同時，本研究也在國立臺灣大學校內建置的試驗場進行入滲試驗，並設定三種相異雨型的降雨事件，將流量計量測到的入滲率與推估之入滲率相比較。研究結果顯示，在不同雨型的條件下，推估結果與流量計量測的數據相近，且解析模式的模擬結果也與數值模式一致，驗證了此方法的正確性與現地應用上的可行性。此推估方法的優點為運算效率高，且不需得知土壤水文地質參數的資訊，僅需了解其熱性質即可進行推估。最後，本模式在邊界與初始條件的適用性較過往的模式更為廣泛，可成為更實用的地下水入滲分析工具。

關鍵字

分散式光纖測溫系統；熱傳輸模式；參數推估；降雨入滲；地溫剖面

並列摘要

Rainfall infiltration is an important source of groundwater recharge, but it is difficult to measure the infiltration rate directly in practice. For example, using traditional double-ring infiltrometers is unable to measure complete infiltration process. Installation of soil moisture meters or manometers requires experts and consumes high costs. Since the heat exchange between the groundwater and soils is incessant and affects the temperature profiles in strata (subsurface temperature profiles, STP), some studies have used the heat as a groundwater flow tracer to observe the interaction between surface water and groundwater for the past few years. Therefore, this study utilizes a distributed temperature sensing system (DTS) to measure the subsurface temperature profiles and develops a new heat-transfer analytical model combined with the optimization method to estimate in-situ infiltration rates. Moreover, this study executes an infiltration test in an experimental field built at the National Taiwan University campus. We set up three rainfall events with different rainfall patterns and compare the infiltration rate measured by a flowmeter with that estimated by the present model and method. The results show that under the different rain patterns, the curves of the estimated infiltration rate are similar to those of the measured infiltration rate. Also, the STP simulated by the developed model are consistent with a numerical model. These validate the correctness of the present method and its feasibility in field application. This estimation method has the advantage of high efficiency in calculation. The information of soil hydrogeological parameters is needless, but only that of soil thermal properties is. Finally, the developed model has more extensive applicability in boundary and initial conditions than previous models, and can become a more useful tool for groundwater infiltration analysis.

並列關鍵字

Distributed temperature sensing systems ； Heat-transfer models ； Parameter estimation ； Rainfall infiltration ； Subsurface temperature profiles

參考文獻

Ahmed, F., M. Borst (2019), Monitoring infiltration rates with time domain reflectometers, Water Environ Res, 91(12), 1638-1649, doi: 10.1002/wer.1165.

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