Groundwater is the major source of drinking in coastal areas and the gradual decline in its quality is a major concern. The present study was aimed to evaluate the groundwater quality and its deterioration in coastal aquifer in the Udupi district of Karnataka state (southwest India) by studying the hydrogeochemical characteristics and salinization processes. We collected 49 groundwater samples from open well to shallow bore wells apart from one surface water sample and one seawater sample during the pre-monsoon season. Samples were analyzed for major ions and oxygen isotopes (δ¹⁸O) and the results reveal that the water is generally acidic to mild alkaline in nature, and the total dissolved solids (TDS) vary from 40 to 12,100 mg/l. δ¹⁸O values (−2.73‰ to −0.6‰) indicate highly saline nature of the groundwater. Widely accepted plots such as Piper plot and Gibbs plot and ratios such as sodium/chloride, chloride/bicarbonate, and calcium/magnesium were used to identify the intrusion of saltwater into the coastal aquifers. The total hardness, Piper plot, and Gibbs plot suggest that the groundwater samples are brackish, mixed, and saline in nature. Based on the seawater percentage (SW%) to quantify the salinization of groundwater, we conclude that the saline water intrusion into the shallow aquifers from seawater is a threat in this region.

地下水是沿海地区主要的饮用水来源，其质量逐渐下降是一个主要问题。本研究旨在通过研究水文地球化学特征和盐碱化过程，评估卡纳塔克邦（印度西南部）乌杜皮地区沿海含水层的地下水质量及其恶化。在季风季节之前，我们从裸眼井到浅井井收集了49个地下水样本，除了一个地表水样本和一个海水样本。分析样品的主要离子和氧的同位素（δ ¹⁸ O），结果表明，该水是通常酸性至在性质弱碱性，总溶解固体（TDS）而变化从40到12100毫克/升。δ ¹⁸O值（-2.73‰至-0.6‰）表示地下水的高盐度性质。使用诸如Piper图和Gibbs图之类的广为接受的图以及诸如钠/氯化物，氯化物/碳酸氢盐和钙/镁之比之类的比例来识别盐水是否侵入沿海含水层。总硬度，Piper图和Gibbs图表明，地下水样品本质上是微咸，混合和含盐的。根据海水百分比（SW％）来定量地下水的盐碱化，我们得出结论，盐水从海水侵入浅层含水层是该区域的威胁。