Hydraulic Properties of Variously Weathered Granitic Bedrock in Headwater Catchments
Hydraulic Properties of Variously Weathered Granitic Bedrock in Headwater Catchments
复制标题
DOI：
10.2136/vzj2008.0142
复制
发表时间：
2009-08
影响因子：
2.8
通讯作者：
S. Katsura;K. Kosugi;T. Mizutani;T. Mizuyama
中科院分区：
文献类型：
--
作者：
S. Katsura;K. Kosugi;T. Mizutani;T. Mizuyama
最近的研究强调了基岩在源头流域发生的水文过程中的重要性。为了了解流过不同风化基岩的水流过程，我们测量了弱风化到强风化田上花岗岩和六甲花岗岩岩芯样本的饱和导水率、Ks 和保水特性。根据这些岩心尺度特性以及岩心形状和原位 Ks 测量，我们定义了两组基岩：CM 级（弱风化）和 CL 至 DL 级（中度至高度风化）。 CM 级基岩岩心几乎没有有效孔隙度（即有效促进水流的孔隙度），因此岩心尺度 Ks 极小，表明基质可被视为本质上不渗透。然而，原位 Ks 远大于岩心尺度值，并且岩心形状显示出明显的裂缝，表明水确实优先流过裂缝。 CL-至DL-级基岩保水曲线的体积含水量在干燥范围内变化不大，但在湿润范围内逐渐变化，导致中等的岩心规模Ks为10−5至10−3 cm s−1 岩心规模Ks值可以通过表征保水曲线的参数很好地解释。原位 Ks 与岩心尺度值的相似性，以及岩心形状中缺乏裂缝，表明水流可以表征为基质流。其他地点的风化花岗岩的水力特性遵循我们地点观察到的趋势，这意味着本研究的结果对各种类型的风化花岗岩具有广泛的适用性。
Recent studies have emphasized the importance of bedrock in hydrologic processes occurring in headwater catchments. To understand water flow processes through variously weathered bedrock, we measured the saturated hydraulic conductivity, Ks, and water retention characteristics of weakly to highly weathered Tanakami granite and Rokko granite core samples. On the basis of these core‐scale properties, along with the core shape and in situ Ks measurements, we defined two groups of bedrock: CM class (weakly weathered) and CL to DL class (moderately to highly weathered). The CM class bedrock cores had almost no effective porosity (i.e., the amount of porosity that effectively contributes to water flow) and therefore extremely small core‐scale Ks, indicating that the matrix could be regarded as essentially impermeable. The in situ Ks was much larger than the core‐scale values, however, and the core shape showed apparent fractures, suggesting that water did flow preferentially through the fractures. The volumetric water content of the CL– to DL–class bedrock water retention curves changed little in the dry range but changed gradually in the wet range, resulting in a moderate core‐scale Ks of 10−5 to 10−3 cm s−1 The core‐scale Ks values were well explained by the parameters characterizing the water retention curve. The similarity of the in situ Ks to the core‐scale values, and the lack of fractures in the core shape, suggested that water flow could be characterized as matrix flow. The hydraulic properties of weathered granite at other sites followed the trends observed at our sites, implying wide applicability of the findings in this study to various types of weathered granite.