Origin of Umm Al Heesh lake in the Rub' Al Khali desert, Saudi Arabia

This paper presents the first detailed hydrogeochemical study of the Umm Al Heesh lake, located in in Rub' Al Khali, Saudi Arabia, the largest continuous sand desert on Earth. Analysis of the salt precipitation, geochemical and isotope facies of the water indicates that the water source of Umm Al Heesh is the Paleocene aquifer groundwater, that naturally seeps to the surface through fractures and forms permanent spring lakes. Because of the topography of the dunes, some water from the spring lakes flows out as surface runoff, creating a large temporary puddle lake. The different groundwater flow between these lakes is reflected in their salinity as well as isotope composition (δ¹⁸O and δ²H). The present study shows that the hydrological configuration with respect to groundwater flow is the predominant factor determining the hydrochemical processes shaping lakes water quality. The continuous interaction between Paleocene aquifer groundwater and lake water is critical to the life and protection of Umm Al Heesh and is determined by a combination of geological, geomorphological, hydrogeological and climatological factors.