Most of the freshwater in the aquifers in the Ningbo Basin has been replaced or mixed with seawater due to transgressions during the Late Pleistocene and Holocene. Only one freshwater lens has been preserved in the central area of the basin. Scholars believe that the deep confined freshwater lens in the Ningbo Basin is connate. However, there is a lack of research focusing on this topic and the evidence is insufficient. The data obtained from monitoring wells suggest that groundwater has been exploited until now. The evolution of the tectonic stress field and fault data for the Ningbo Basin indicate that the concealed NE- and NW-trending faults are likely water-conducting. Thus, the following hypothesis was put forward: the deep confined aquifers were recharged upward by the fissure water of the concealed faults. A series of tests and analyses of hydrochemical ions and various isotopes of the deep confined water were carried out, and two sets of hydrogeochemical and isotopic data obtained in November 2017 and May 2018 were compared. The ³H activity indicates notable recharge of the aquifers with modern water. The significant correlation between the ¹⁴C age and the ²²²Rn activity indicates rapid groundwater replacement in several sampling wells. The location of these sampling wells is related closely to the concealed faults. Thus, the hypothesis can be confirmed; the deep confined aquifers were recharged by modern water from the bottom and the concealed faults provided the access.

由于晚更新世和全新世的海侵，宁波盆地含水层中的大部分淡水已经被海水替代或混合。在盆地的中心区域只保存了一个淡水透镜体。学者认为，宁波盆地深层承压淡水透镜体是与生俱来的。然而，缺乏针对这一主题的研究，证据不足。从监测井中获得的数据表明，地下水一直被开采到现在。宁波盆地的构造应力场演化和断层资料表明，隐伏的NE向和NW向断层可能具有导水作用。因此，提出以下假设：深部承压含水层被隐伏断层的裂隙水向上补给。对深层承压水的水化学离子和各种同位素进行了一系列测试分析，对比了2017年11月和2018年5月获得的两组水文地球化学和同位素数据。这³ H 活动表明现代水对含水层的显着补给。¹⁴ C 年龄和²²² Rn 活性之间的显着相关性表明在几个采样井中地下水快速替代。这些采样井的位置与隐蔽断层密切相关。因此，可以证实假设；现代水从底部补给深层承压含水层，隐藏的断层提供了通道。