orologio en Altadefinizione. Rocks, dunes, sand and dust - large areas of Namibia in southwest Africa are characterized by deserts. Riverbeds full of sand meander through these inhospitable regions. Some of these only have water once every few years when enough rain has fallen in the mountains and the water rushes to the coast - but most of the time the river courses have dried up. And yet they are crucial for the survival of many living beings.