Out of the dozen or so times I've been there (boating or biking trips) there was only one time water was not available from the tap - and that time a ranger was present who shuttled me over to a big garage full of 5 gallon water jugs so I could fill up. So, a perfect track record for me.
If for some reason there is no water available from the tap (unlikely), the big muddy is 100% guaranteed to be flowing. It's never been dry at Westwater in my lifetime
![Smiley](http://www.bikepacking.net/forum/Smileys/Lots_O_Smileys/icon_biggrin.gif)
It will require filtering though and as warm as it's been recently it will be heavily silted.