Kingdoms of Arda is a Singleplayer & Multiplayer total conversion of Mount & Blade II Bannerlord, that brings the world of Tolkien into the game. This includes: characters, locations, weapons etc. from The Lord of the Rings, The Hobbit, Silmarillion and other works by Tolkien and media made for his universe.
But...where is the river???!! :P
I was stationed in a desert for 9 months so maybe I can answer this. In the desert rivers can only be really seen during the rainy season (usually winter), and only after a heavy rainfall. Those ditches in the sand are where the rivers would run. Realistically, there would also be more plant life in the river areas, even during the dry season (bushes and such), so that from an airplane you could see exactly where the river would be running just by looking for paths of greenery.
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