While previous studies conclude that riparian freshwater lenses are the result of buoyancy forces that drive river water circulation in the adjacent aquifer, only highly idealised conceptual models have been assessed. A numerical study is conducted to investigate the influence of evaporation from unsaturated bare soils, including accumulation and precipitation of salt, on riparian freshwater lenses, assuming otherwise similar conditions to those adopted in recent studies. Non‐evaporating simulations that account for unsaturated zone, are firstly compared to previous saturation‐only numerical and analytical results, and reasonable matches are obtained. The modelling analysis of evaporative simulations includes three different approaches to the treatment of solute in evaporated water: (a) no evaporative salt accumulation, (b) evaporative salt accumulation, and (c) as for (b), except resistance to evaporation caused by salt accumulation is considered. Significant evaporative fluxes caused gaining river conditions to change to losing conditions, leading to the cessation of buoyancy‐driven freshwater circulation and to freshwater bodies that are not lenticular. Rather, evaporation reduces regions where the watertable and/or unsaturated zone are fresh relative to the freshwater lens volume. Evaporation rates depend on the hydraulic connection between the floodplain surface and watertable, which is limited where the watertable is deep, the soil hydraulic conductivity is low, and under higher potential evaporation rates. The results show that floodplain evaporation may control the freshwater‐saltwater distribution, and lead to hypersaline groundwater under certain conditions, although earlier buoyancy‐driven conceptual models of riparian lenses appear to remain valid where the thickness of the unsaturated zone is sufficiently large.

中文翻译：

---

蒸发和盐分对河岸淡水透镜体的影响

虽然之前的研究得出结论，河岸淡水透镜体是驱动相邻含水层中河水循环的浮力的结果，但只评估了高度理想化的概念模型。进行了一项数值研究，以研究非饱和裸土的蒸发（包括盐分的积累和沉淀）对河岸淡水透镜体的影响，假设其他条件与最近的研究采用的条件相似。首先将考虑非饱和区的非蒸发模拟与之前仅饱和的数值和分析结果进行比较，并获得合理的匹配。蒸发模拟的建模分析包括处理蒸发水中溶质的三种不同方法：(a) 无蒸发盐积累，(b) 蒸发盐分积累，和 (c) 与 (b) 相同，但考虑到盐分积累引起的蒸发阻力。显着的蒸发通量导致河流条件从上升条件转变为失去条件，导致浮力驱动的淡水循环停止和淡水水体不是透镜状的。相反，蒸发减少了相对于淡水透镜体体积的水位和/或不饱和区是新鲜的区域。蒸发率取决于漫滩表面和地下水位之间的水力联系，在水位较深、土壤导水率低和潜在蒸发率较高的情况下，水力联系受到限制。结果表明，漫滩蒸发可能控制淡水-咸水分布，