應用攜帶式鑽探設備觀測天然林沖蝕溝的地表逕流及淺層地下水特性

Applying Portable Drilling Equipment to Explore the Characteristics of Surface Runoff and Shallow Groundwater along a Gully in a Natural Forest

蕭維震(Wei-Chen Hsiao) ； 梁偉立(Wei-Li Liang)

《中華水土保持學報》 52卷3期 (2021/09) Pp. 121-134

https://doi.org/10.29417/JCSWC.202109_52(3).0001

摘要

臺灣山高流急且降雨時空分布不均，水資源的永續利用是一個重大的議題，即便山區地下蘊含大量水資源，但國內有關山區地下水的研究侷限於深層地下水，對於山區淺層地下水的特性仍缺乏高空間解析度的資訊。為了釐清臺灣集水區源頭部淺層地下水的反應特性，本研究利用攜帶式鑽探設備於天然林沖蝕溝鑽鑿7口水井以觀測淺層地下水位，並建置簡易量水堰以利觀測地表逕流量。沖蝕溝的崩積層地層結構複雜，無法單憑地層結構判釋淺層地下水深度，需透過攜帶式鑽探設備的直接鑽探才可掌握地下水位深度。地下水動態依坡地區段而異，淺層地下水位最深與水位變動幅度最大的位置皆位於沖蝕溝中段，且中上段為水脈分散處，地表與地下的水文連結性弱。中下段為水脈匯集處，地表與地下的水文連結性強，而此水脈的流動型態屬於伏流水。本研究證實攜帶式鑽探設備可適用於臺灣山區的淺層地下水觀測，除了釐清源頭集水區的降雨逕流機制外，也有助於山區水資源的評估。

關鍵字

崩積層 ； 伏流水 ； 攜帶式鑽探設備 ； 淺層地下水

並列摘要

Sustainable utilization of water resources is a critical concern in Taiwan because of the island's environment features including mountainous topography, rapid surface flow, and uneven distribution of rainfall in time and space. Although groundwater resources are abundant in mountainous areas, most studies on groundwater monitoring in mountainous environments in Taiwan have focused on deep groundwater. By contrast, high-spatial-resolution information on shallow groundwater characteristics remains lacking. To determine the dynamics of shallow groundwater in headwater catchments in Taiwan, this study installed seven groundwater wells using portable drilling equipment and constructed simple weirs to monitor surface runoff at several locations along a gully in a natural forest. The geological structure of the gully was heterogeneous and could be classified as colluvium. The depth of the groundwater table could not be estimated using geological structure information; however, it could be directly detected by boring using the portable drilling equipment. The dynamics of the groundwater varied with the locations along the gully. The deepest point of the shallow groundwater and the largest variations in the shallow groundwater table were both observed at the middle slope. Shallow groundwater pathways were divergent at the upper-middle slope where the hydrological connectivity between surface runoff and shallow groundwater was weak. By contrast, shallow groundwater pathways were convergent at the lower-middle slope where the hydrological connectivity between surface runoff and shallow groundwater was strong. The flowing pattern of shallow groundwater could be classified as hyporheic flow. This study demonstrated that portable drilling equipment can be effectively employed for shallow groundwater observations in mountainous areas in Taiwan; this approach can help to clarify the mechanism of rainfall-runoff processes in headwater catchments and to evaluate the water resources in mountainous environments.

並列關鍵字

colluvium ； hyporheic flow ； portable drilling equipment ； shallow groundwater