General description
Kebili is a Tunisian governorate located in the southwest of Tunisia. The study was carried out in the continental oasis of Guettaaya (Ettillaat) in Kebili which is located in the south of Tunisia. This oasis is located between 8.27° to 8.29° N latitude and 33.24° to 33.26° E longitude (Ibrahim et al., 2019). The oasis is adjacent to and west of Chott El Djerid, a salt plain.
Climate context
The oasis of Guettaaya, also called oasis of Etillat, is characterized by a desert climate, the annual rainfall is irregular and less than 90 mm, and the temperature is very high during the summer (maximum 55°C in July). Evaporation can reach 2000 mm per year. In spring and summer, the strong and hot winds of the sirocco blow carrying the sands of the desert towards the oasis.
Geological background
The site is located on a flat plain composed of Holocene lacustrine sediments, which developed mainly in the form of alluvium and evaporites. To the north, the area is bounded by the Saharan Atlas Mountains, while to the south are dunes that are part of the Grand Erg Oriental. The depression at this site is mostly filled with erosional material from the north and aeolian material carried by southerly winds, as well as evaporite deposits. A characteristic feature of the area is the presence of gypsum crusts on the ground surface.
Edaphic context
The soils of the Etillat oasis are classified as Gypsisols according to the WRB classification. The sandy soils of the oasis are characterized by high permeability and low water retention (Kadri and Van Ranst, 2002). The salinity of groundwater and soil varies with the depth of the water table. The study area is irrigated by a surface irrigation system. The plots of the date palm plantations are connected to drainage collectors installed in the saline depression of Chott El Djerid.
The vegetation cover of the oasis of Etillat is mainly composed of date palms (Phoenix dactylifera L.) of the Deglet Nour variety, and fodder alfalfa (Medicagosativa) for its high salt tolerance.
This site located in an oasis ecosystem is representative of many palm groves in southern Tunisia.