干旱区生态环境知识资源中心(Arid): Oblique Porous Composite as Evaporating Cap: Do Desert Dunes Preserve Moisture by Capillary Barriers and Tilt of Their Slopes?

Arid

DOI	10.1029/2018WR024526
	Oblique Porous Composite as Evaporating Cap: Do Desert Dunes Preserve Moisture by Capillary Barriers and Tilt of Their Slopes?
	Al-Shukaili, A.1; Al-Busaidi, H.1; Al-Maktoumi, A.1; Abdalla, O.2; Shelukhina, O.2; Kacimov, A. R.1
通讯作者	Al-Shukaili, A.
来源期刊	WATER RESOURCES RESEARCH
ISSN	0043-1397
EISSN	1944-7973
出版年	2019
卷号	55 期号:3 页码:2504-2520
英文摘要	Evaporation from desert sand dunes is studied practically using laboratory columns and mathematically using both analytical and numerical modeling. On outcropping cliffs of the dunes of Buwshar (Oman), microstratification, with layers' thickness of 1-2mm, was observed. Loose sand and consolidated core samples were collected for laboratory experiments. Imbibition into initially dry sand columns and ensuing steady state evaporation from a capillary fringe above a horizontal water table were studied. The evaporating, negative-pressure topsoil of the columns was slanted mimicking the cliffs' tilt. In the columns plugged by a thin composite cap made by tooling the dune stratified clod, evaporation was impeded and reduced as compared with a homogeneous column. The same outlet evaporating boundaries were considered in HYDRUS-2D simulations, which showed that 2-D evaporation from a homogenous column was significantly higher than that from the column with a stratified plug at the top. Analytical solution for a 2-D tension-saturated homogeneous trapezium was obtained by conformal mappings of pentagon in the physical plane onto a rectangle in the Zhukovsky plain, via a reference plane. This solution combines the versatility of the Toth model, where topology of flow is controlled by an isobaric boundary of a flow tube, and of the Vedernikov model, which assumes a constant hydraulic conductivity in the negative pressure zone of a capillary fringe. Analytical formulae also manifest a decrease of the flow rate with the increase of the angle of tilt of an evaporating isobar. Plain Language Summary Some sand dunes in arid deserts have moist volumes at relatively shallow depths under their dry and hot slopes. This perplexing water accumulation has been attributed to several factors, for example, dew and vapor condensing from the wind air of high humidity or stratification of aeolian deposits and ensuing capillary barriers to vertical infiltration after rare rainfall events. In this note we explore a potential impedance to a trivial 1-D evaporation from a fully saturated horizon to a negative pressure isobar, stemming from its wavy (zig-zag) shape and a thin oblique microstratified cap composed of millimeter-thick layers. Our laboratory experiments with two sand columns (one homogeneous, with a tilted soil surface and another covered by a tilted cap) showed that the total steady state evaporation from a heterogeneous column is less, provided the volumes of the two are the same. This is confirmed in HYDRUS-2D numerical simulations for trapezoidal domains. Analytical solutions illustrate the decrease of evaporation losses if the area of a homogeneous trapezium is fixed along the minimum distance between the inlet (water table) and outlet (soil surface), provided the soil is tension saturated.
英文关键词	capillary barrier dune hydrology evaporation HYDRUS modeling soil column experiment Vedernikov-Toth's model
类型	Article
语种	英语
国家	Oman
收录类别	SCI-E
WOS记录号	WOS:000464660000039
WOS关键词	SOIL-WATER ; SAND DUNES ; FLOW ; SEEPAGE ; INFILTRATION ; HILLSLOPE ; PATTERNS ; RECHARGE ; AGE
WOS类目	Environmental Sciences ; Limnology ; Water Resources
WOS研究方向	Environmental Sciences & Ecology ; Marine & Freshwater Biology ; Water Resources
资源类型	期刊论文
条目标识符	http://119.78.100.177/qdio/handle/2XILL650/219288
作者单位	1.Sultan Qaboos Univ, Dept Soils Water & Agr Engn, Muscat, Oman; 2.Sultan Qaboos Univ, Dept Earth Sci, Muscat, Oman
推荐引用方式 GB/T 7714	Al-Shukaili, A.,Al-Busaidi, H.,Al-Maktoumi, A.,et al. Oblique Porous Composite as Evaporating Cap: Do Desert Dunes Preserve Moisture by Capillary Barriers and Tilt of Their Slopes?[J],2019,55(3):2504-2520.
APA	Al-Shukaili, A.,Al-Busaidi, H.,Al-Maktoumi, A.,Abdalla, O.,Shelukhina, O.,&Kacimov, A. R..(2019).Oblique Porous Composite as Evaporating Cap: Do Desert Dunes Preserve Moisture by Capillary Barriers and Tilt of Their Slopes?.WATER RESOURCES RESEARCH,55(3),2504-2520.
MLA	Al-Shukaili, A.,et al."Oblique Porous Composite as Evaporating Cap: Do Desert Dunes Preserve Moisture by Capillary Barriers and Tilt of Their Slopes?".WATER RESOURCES RESEARCH 55.3(2019):2504-2520.