Evaporation and salt accumulation effects on riparian freshwater lenses

doi:10.1029/2019WR026380

Abstract

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.

DOI	10.1029/2019WR026380
	Evaporation and salt accumulation effects on riparian freshwater lenses
	Ilja America; Chenming Zhang; Adrian D. Werner; Sjoerd E. A. T. M. van der Zee
	2020-08-03
发表期刊	Water Resources Research
出版年	2020
英文摘要	Abstract 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.
领域	资源环境
URL	查看原文
引用统计	被引频次：13[WOS] [WOS记录] [WOS相关记录]
文献类型	期刊论文
条目标识符	http://119.78.100.173/C666/handle/2XK7JSWQ/287767
专题	资源环境科学
推荐引用方式 GB/T 7714	Ilja America,Chenming Zhang,Adrian D. Werner,et al. Evaporation and salt accumulation effects on riparian freshwater lenses[J]. Water Resources Research,2020.
APA	Ilja America,Chenming Zhang,Adrian D. Werner,&Sjoerd E. A. T. M. van der Zee.(2020).Evaporation and salt accumulation effects on riparian freshwater lenses.Water Resources Research.
MLA	Ilja America,et al."Evaporation and salt accumulation effects on riparian freshwater lenses".Water Resources Research (2020).

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