Marine intrusion phenomenon is the main phenomenon threatening the groundwater quality in coastal aquifers around the world. This phenomenon is generally caused by the overexploitation of aquifers, decline in the piezometric level and the rise in sea level under the climate change effect. There are several approaches to study and assess the marine intrusion phenomenon. For this study, the crossing of piezometric, hydrochemical and isotopic approaches was adopted to highlight the state of this phenomenon within the Plio-quaternary aquifer of the Essaouira basin. The couples (Na, Cl), (Ca, Mg), (Br, Cl), (δ2H, δ18O), (δ18O, Cl) were determined for 24 samples capturing the shallow aquifer of the Essaouira basin. The piezometric approach shows that negative piezometric levels are registered. The ionic ratios Br/Cl close to 1.5 and 1.7‰, Na/Cl close to 0.86, Mg/Ca and SO4/Cl weak showed that the seawater begins to invade the freshwater of the Plio-quaternary aquifer of Essaouira basin. This intrusion demonstrated by ionic ratios and corroborated by isotopic approach and the combined use of oxygen-18 contents and chlorides has a mixing rate of 15.9% at the well 11/51, 14.5% at the sample 45/51, 13.2% at the well 149/51, 13.3% at point O114 and 12.8% at the well O94. However, the results of the hydrogeochemical and isotopic approach suggest intrusion up to 2 km from the sea; this reflects a warning sign about the groundwater deterioration of the study area.

中文翻译：

---

海水从半干旱环境侵入沿海含水层，以索维拉盆地冲积含水层为例（摩洛哥）

海洋入侵现象是威胁全球沿海含水层地下水质量的主要现象。这种现象一般是由于含水层过度开采、测压水位下降和气候变化作用下海平面上升造成的。有几种方法可以研究和评估海洋入侵现象。在这项研究中，采用了测压法、水化学和同位素方法的交叉，以突出索维拉盆地 Plio-第四纪含水层内这种现象的状态。对捕获索维拉盆地浅层含水层的 24 个样品确定了 (Na, Cl), (Ca, Mg), (Br, Cl), (δ2H, δ18O), (δ18O, Cl) 对。测压法显示负测压水平被记录。离子比 Br/Cl 接近 1.5 和 1.7‰，Na/Cl接近0.86，Mg/Ca和SO4/Cl弱表明海水开始侵入索维拉盆地上新第四纪含水层的淡水。这种侵入由离子比率证明并由同位素方法证实，氧 18 含量和氯化物的组合使用在井 11/51 处的混合率为 15.9%，在样品 45/51 处为 14.5%，在井处为 13.2% 149/51，O114 点为 13.3%，O94 井为 12.8%。然而，水文地球化学和同位素方法的结果表明，入侵距离海洋可达 2 公里；这反映了研究区地下水恶化的警告信号。这种侵入由离子比率证明并由同位素方法证实，氧 18 含量和氯化物的组合使用在井 11/51 处的混合率为 15.9%，在样品 45/51 处为 14.5%，在井处为 13.2% 149/51，O114 点为 13.3%，O94 井为 12.8%。然而，水文地球化学和同位素方法的结果表明，入侵距离海洋可达 2 公里；这反映了研究区地下水恶化的警告信号。这种侵入由离子比率证明并由同位素方法证实，氧 18 含量和氯化物的组合使用在井 11/51 处的混合率为 15.9%，在样品 45/51 处为 14.5%，在井处为 13.2% 149/51，O114 点为 13.3%，O94 井为 12.8%。然而，水文地球化学和同位素方法的结果表明，入侵距离海洋可达 2 公里；这反映了研究区地下水恶化的警告信号。