Hydrogeological characterization of the Kosi Bay Lakes system, north-eastern South Africa
Hydrogeological characterization of the Kosi Bay Lakes system, north-eastern South Africa
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南非东北部科西湾湖泊系统的水文地质特征
DOI：
10.1007/s12665-016-6164-6
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发表时间：
2016
影响因子：
2.8
通讯作者：
M. Demlie
中科院分区：
文献类型：
--
作者：
M. Ndlovu;M. Demlie
本文报道了一个依赖地下水的湖泊系统，位于南非东北海岸的湖泊科西湾流域的水文地质特征。在研究中应用了常规水文地质技术，包括水平衡分析、水文地球化学和环境同位素方法。该地区有三个不同的含水层系统，即无压全新世盖层砂、科西湾和Port Durnford地层以及Umkhwelane和Uloa地层。使用氯质量平衡法估计，与湖泊相连的最高含水层的地下水补给量为年平均降水量的12%（MAP = 939 mm/a）。湖泊蒸发量和流域蒸散量分别为1310和1135 mm/a。年平均水量平衡分量表明投入和产出之间正平衡。地下水从西部通过湖泊（流通湖）流入印度洋。浅层全新世含水层和溪流中的地下水具有相似的水化学和同位素特征，表明存在很强的相互联系。这些地下水和溪流的水化学主要为Na-Cl-HCO 3水，盐度极低（88 - 400 µS/cm），同位素特征为负（δD和δ 18 O值为负）。这些湖泊的水化学类型为Na-Cl水，盐度范围为1014至25，300 µS/cm，正稳定同位素特征（正δD和δ 18 O特征）表明蒸发作用较强。研究进一步揭示了从南到北，朝着河口的湖泊之间的盐度和同位素序列。
This paper reports a hydrogeological characterization of a groundwater-dependent lakes system, the Lakes Kosi Bay catchment located in the north-eastern coast of South Africa. Conventional hydrogeological techniques including water balance analysis, hydrogeochemical and environmental isotope methodologies were applied in the study. Three distinct aquifer systems are recognized in the area, namely the unconfined Holocene cover sands, the Kosi Bay and Port Durnford Formations, and the Umkhwelane and Uloa Formations. Groundwater recharge to the topmost aquifer, which is connected to the lakes, is estimated using the chloride mass balance method to be 12 % of the mean annual precipitation (MAP = 939 mm/a). Evaporation rate from the lakes and evapotranspiration from the catchment are 1310 and 1135 mm/a, respectively. The mean annual water balance components indicate a positive balance between inputs and outputs. Groundwater flows from the west through the lakes (flow-through lakes) to the Indian Ocean. Groundwater in the shallow Holocene aquifer and streams has similar hydrochemical and isotopic signature indicating strong interconnection. These groundwater and streams have a hydrochemistry dominated mainly by a Na–Cl–HCO3 water type, a very low salinity (ranging from 88 to 400 µS/cm) and a negative isotopic signature (negative δD and δ18O values). The lakes are characterized by Na–Cl hydrochemical water type, have salinity that ranges from 1014 to 25,300 µS/cm, and positive stable isotopic signature (positive δD and δ18O signature) indicating strong evaporation effects. The study further reveals a salinity and isotopic series among the lakes from south to north, towards the estuary.