This doesn't compute. Two quarts of water consumed on a three mile hike taking four hours and some amount refilled half way...There must be something other than dehydration involved.

It is nice to know that it was 94 in Tucson that day, but Tucson is significantly lower than the state park, although the group would have been dealing with reflected heat off of upright surfaces, etc.

For a typical individual, nearly a gallon of water would have been more than enough to complete this excursion comfortably, provided any degree of adequate hydration at the beginning.