Geo-Environmental Study on Wadi Metaam in the Ibex Protectorate, Central Saudi Arabia

Abstract

The present study is an attempt to demonstrate how geology, climate and plant cover interact in carving the environment.  It is update knowledge and understanding of the plant diversity. It determines the impact of application of protection of wildlife on land cover, and illustrates how the laws of environmental protection help in preserving the natural and wildlife at Wadi Metaam and its tributaries in the Ibex Protectorate, Saudi Arabia.

The study demonstrates that Wadi Metaam was excavated at Tuwaiq Escarpment (Mountain) at the periphery of the Najd Plateau. It is made of limestone from the Middle-Upper Jurassic epoch; during that time, the climate was humid enough to allow for excavation of Wadi Metaam and its tributaries for more than 400 m through the escarpment.SPOT+5 images acquired for the years 2004, 2010, and 2013 and used to produce unsupervised and supervised classifications. The drainage of Wadi Metaam and its tributaries reflects a dendritic pattern. The drainage basin is at Al-Onouk, has an elevation of 1125 m, and slopes down along Abu Kaff toward three tributaries: Wadi Al-Ghaba (4^th order), Wadi Ghafar (4^th order), and Wadi Al-Agma (3^rd order). These are connected at Al-Molakatt to form the major Wadi Metaam. While the watershed area receives about 150 mm/yr of rainwater at Al-Ounouk, the situation is completely different at Wadi Metaam, where only 28 mm/yr of rainwater is received. These rains enrich Wadi Metaam with a wide diversity of shrubs and herbal perennial plants and sculpt its geomorphic features, which include karstfication and sinkholes. In Saudi Arabia’s ambitious plan to secure water, the government has established a concrete dam 903 m long and 15 m high to store up to 10 million m³ of rainwater. However, the dam has never been filled to more than half of its capacity. The collected plant samples represent four different sites; these are the open area at Wadi Metaam floor, the talus slopes, Tuwaiq Mountain, and the fenced area at Wadi Al-Ghaba. The density and plant cover in the fenced area are 53.80p/area and 43.22p/area, respectively, and decrease to 21.55p/area and 25.15p/area in the open area. The results reflect the impact of protection to increase plant species in general and plant species with nutritional value in particular.The most popular identified plants are 21 perennial plant species belonging to 15 families: Acacia gerrardii, Acacia tortilis, and Acacia ehrenbergiana (Mimosaceae), Anvillea garcinii and Rhanterium epapposum (Asteraceae), Blepharis ciliaris (Acanthaceae), Calotropis Procera (Asclepiadaceae), Citrullus colocynhis, and Cucumis prophetarum (Cucurbitaceae), Haloxylon solicomicum (Chenopodiaceae), Lycium shawii (Solanaceae), Ziziphus nummularia (Rhamnaceae), Zygophyllum migahidi, and Fagonia bruguieri (Zygophyllaceae), Panicum turgidum (Poaceae), Zilla spinosa (Brassicaceae), Rhazya stricta (Apocynaceae), Cleome amblyocarpa, and Capparis sinaica (Capparaceae), Convolvulus oxyphyllus (Convolvulaceae), and Heliotrapium bacciferum (Boraginacae).

Keywords: geomorphology, remote sensing, plant cover, Wadi Metaam, Ibex Protectorate, Saudi Arabia