It will be much drier than normal, but the river will be flowing, and you will never be very far from it for very long except for a few places: the Muir Gorge "bypass" and the long climb from Pate Valley to Harden Lake. According to Schaffer Morrison Creek can dry out, and it can be a hot climb out of Pate Valley--assuming you are doing the GCT downriver.
And to those who have asked on other threads: yes, the GCT is worth doing even in a dry year. The water will be low and the waterwheels will be absent, but you will have calm, clear pools for swimming or cooling off and the ability to explore and camp on the otherwise inaccessible "other" side of the river--there are limited campsites on the trail side between Pate Valley and Glen Aulin. Enjoy!
