Why at Sahara desert there is sand and not water?

The Sahara Desert has predominantly sandy terrain due to its arid climate, characterized by low precipitation and high evaporation rates. Over millions of years, geological processes and wind erosion have shaped the landscape, leading to the formation of sand dunes and eroded rock formations. Although the Sahara was once covered by water during ancient times, climatic changes shifted it to a desert environment, resulting in the current sandy conditions.