Seawater intrusion into coastal aquifers is a global problem as it limits the freshwater availability in coastal regions. A study has been conducted with the aims to identify the processes controlling seawater/freshwater distribution and demarcate potential freshwater zones in an aquifer along the coast of Bay of Bengal. Sixty-eight groundwater samples were collected from 900 sq. km spread along the coast and were analyzed for various physicochemical parameters. Most of the samples show brackish to saline characteristics. The anionic ratio indicates that 65% of groundwater samples are slightly to moderately affected by seawater, while 25% are severely affected. Seawater–freshwater mixing and freshening have been identified as the dominant processes in controlling the groundwater chemistry. Seawater has been traced in 88% of collected samples, and it is found that only 1% mixing of the seawater makes the groundwater unsuitable for drinking purposes. The fraction of seawater in individual samples has been calculated using chloride as a tracer. Thematic maps of seawater tracers have indicated that groundwater with higher salinity is located in the inland areas, whereas patches of fresh groundwater are found near the coast. With the help of satellite imageries, it has been found that the freshwater patches are typically located on paleochannels and sand dunes, which act as local reservoirs to retain freshwater in the seawater affected region. Such geomorphic features are common in coastal environments. Their identification and subsequent utilization as freshwater sources can be of vital importance to deal with freshwater scarcity in the coastal regions across the globe.

中文翻译：

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沿海地区地貌特征与地下水质量和淡水供应量的关系

海水侵入沿海含水层是一个全球性问题，因为它限制了沿海地区的淡水供应。进行了一项研究，旨在确定控制海水/淡水分布的过程，并在孟加拉湾沿岸的含水层中划定潜在的淡水区域。收集了沿海岸900平方公里的68个地下水样品，并分析了各种理化参数。大多数样品显示出咸至咸的特性。阴离子比值表明65％的地下水样品受到海水的轻微至中度影响，而25％的海水受到严重影响。海水-淡水混合和清新已被确定为控制地下水化学的主要过程。在88％的采集样品中都追踪到了海水，结果发现，海水中只有1％的混合，使地下水不适合饮用。已使用氯化物作为示踪剂计算了单个样品中海水的比例。海水示踪剂的专题图表明，盐度较高的地下水位于内陆地区，而沿海附近则发现了一些新鲜的地下水。在卫星图像的帮助下，已发现淡水斑块通常位于古河道和沙丘上，它们是当地的水库，将淡水保留在受海水影响的地区。这种地貌特征在沿海环境中很常见。将其识别并随后用作淡水源对于应对全球沿海地区的淡水短缺至关重要。