75
global watershed map
(lemmy.world)
source: https://decolonialatlas.wordpress.com/2017/04/18/colorful-river-basin-maps/
It has more detailed maps for each continent too.
This is just a guess, but looking at satellite images it looks like there could be dry river beds in the desert. Maybe the area gets enough rain to have them, but not enough for them to lead anywhere.