I asked Elijah if we could rise before nightfall and go off our current vector to check over in the area where the barking had ceased.
It also meant a little back tracking, but ended up worthwhile. The sand gave way to bedrock and after a short search we found some water in a pool on the rock surface. It had been fouled by the presence of animals. Unclean for sure.
Elijah found the close by pump and basin whose spillage fed the other. (He practically tripped over it in the darkness).
We were back on track, so we decided to halt and rest.
With the dawn we were able to reacquire our bearings before taking up our alternating watches.