Informations et ressources scientifiques
sur le développement des zones arides et semi-arides

Titre : The effect of stratification on sand dunes hydrology in arid zone environments : case of Oman

Auteur : Al-Shukailiyah, Afrah Hamed Hamdan.

Université de soutenance : Sultan Qaboos University

Grade : Master of Science (MS) in Soil and Water Mangement 2018

Résumé partiel
Sand dunes occupy large areas of Ash Sharqiah Sands and Empty Quarter in Oman. Accumulation of aeolian sand dunes also takes place in some cities (e.g. Buwshar dunes in Muscat). In Oman, like other arid-zone countries, sand dunes receive sparse rainfall events. The infiltration and percolation of rainwater might be trapped within sand dunes and create zones of high water saturation inside. Heterogeneity of soil and layered (stratified) texture of the dune bodies reduces infiltration, evaporation and redistribution of soil moisture. In order to have a good understanding of sand dunes hydrology, it is important to investigate moisture and temperature fluxes in the desert sand dunes. In this thesis, the main objective was to study a combined effect of a nonflat topography (dune slope) and capillary barrier (created by topsoil textural structuring) on evaporation from a saturated zone beneath (e.g. a perched water table or retained wet spot in the dune interior). Buwshar’s sand dunes (Oman) were selected to estimate evaporation from desert sand dunes. During field visits, microstratification (lamination) on outcropping cliffs, with layers’ thickness of 1-2 mm and tilted at a slope of about 35 ° was described. Loose sand and consolidated rock samples were collected for laboratory experiments. Microscopic analysis was conducted to determine porosity and mineral composition. The evaporation rate and cumulative evaporation from vertical sand columns, 20-40 cm tall, capped by porous stratified "plugs”, about 3 cm thick, were measured. Numerically, HYDRUS-2D software was used to simulate the column experiments by considering trapezoidal flow tubes with and without a tilted stratified "plug”. Transient distributions of the pressure head, moisture content, and Darcian flux were obtained. Laboratory and microscopic analysis evidenced that the micro-stratified structures, common in sand dunes, have particle sizes about two times larger than loose sands from the same area.

Présentation (SHUAA)

Annonce (Almandumah)