Groundwater Research Group, Queen's University Belfast, BT9 5AG, Northern Ireland, United Kingdom.
Groundwater Research Group, Queen's University Belfast, BT9 5AG, Northern Ireland, United Kingdom.
Sci Total Environ. 2014 Dec 1;500-501:224-34. doi: 10.1016/j.scitotenv.2014.08.105. Epub 2014 Sep 15.
Identifying groundwater contributions to baseflow forms an essential part of surface water body characterisation. The Gortinlieve catchment (5 km(2)) comprises a headwater stream network of the Carrigans River, itself a tributary of the River Foyle, NW Ireland. The bedrock comprises poorly productive metasediments that are characterised by fracture porosity. We present the findings of a multi-disciplinary study that integrates new hydrochemical and mineralogical investigations with existing hydraulic, geophysical and structural data to identify the scales of groundwater flow and the nature of groundwater/bedrock interaction (chemical denudation). At the catchment scale, the development of deep weathering profiles is controlled by NE-SW regional scale fracture zones associated with mountain building during the Grampian orogeny. In-situ chemical denudation of mineral phases is controlled by micro- to meso-scale fractures related to Alpine compression during Palaeocene to Oligocene times. The alteration of primary muscovite, chlorite (clinochlore) and albite along the surfaces of these small-scale fractures has resulted in the precipitation of illite, montmorillonite and illite-montmorillonite clay admixtures. The interconnected but discontinuous nature of these small-scale structures highlights the role of larger scale faults and fissures in the supply and transportation of weathering solutions to/from the sites of mineral weathering. The dissolution of primarily mineral phases releases the major ions Mg, Ca and HCO3 that are shown to subsequently form the chemical makeup of groundwaters. Borehole groundwater and stream baseflow hydrochemical data are used to constrain the depths of groundwater flow pathways influencing the chemistry of surface waters throughout the stream profile. The results show that it is predominantly the lower part of the catchment, which receives inputs from catchment/regional scale groundwater flow, that is found to contribute to the maintenance of annual baseflow levels. This study identifies the importance of deep groundwater in maintaining annual baseflow levels in poorly productive bedrock systems.
确定基流的地下水来源是地表水特征描述的重要组成部分。戈尔廷利夫流域（5 平方公里）由卡里甘斯河的源头溪流网络组成，该河本身是爱尔兰西北部福伊尔河的支流。基岩由生产能力差的变质沉积物组成，其特征是断裂孔隙率。我们介绍了一项多学科研究的结果，该研究将新的水文化学和矿物学调查与现有的水力、地球物理和结构数据相结合，以确定地下水流动的规模以及地下水/基岩相互作用（化学剥蚀）的性质。在流域尺度上，深风化剖面的发育受与格兰扁造山运动期间山脉建造相关的 NE-SW 区域尺度断裂带控制。在古近纪到始新世期间阿尔卑斯挤压作用下，与微到中尺度裂缝相关的原地矿物相化学剥蚀控制着矿物的化学风化。这些小规模裂缝表面上的原生白云母、绿泥石（斜绿泥石）和钠长石的蚀变导致伊利石、蒙脱石和伊利石-蒙脱石粘土混合物的沉淀。这些小规模结构的相互连接但不连续的性质突出了更大规模断层和裂隙在风化溶液从矿物风化点向/到供给和输送中的作用。主要矿物相的溶解释放出 Mg、Ca 和 HCO3 等主要离子，这些离子随后构成地下水的化学成分。钻孔地下水和溪流基流水文化学数据用于约束影响整个溪流剖面地表水化学的地下水流动路径的深度。结果表明，主要是接收流域/区域尺度地下水输入的流域下部，被发现有助于维持年度基流水平。本研究确定了深部地下水在维持低生产力基岩系统年度基流水平方面的重要性。
