One other key fact to remember is that courses overwhelmingly irrigate with non-potable water. In Georgia at least I do not know of a single course that uses drinking water to irrigate.
Homeowners use drinkable water most often as they tap into city lines for their irrigation systems (few in suburbia have their own wells or lakes). Homeowners also use far more water and herbicides per acre than golf courses.
My course is 200 acres within a CUP instead of 1300 more homes (as allowed by current zoning). I take the run off water, capture it, irrigate with it before it heads into the river and this is clearly preferable to having that same water run directly from the neighborhood into the river.
The 1400 people stat I am not sure of either but that is a per person not a per household figure. Also I am not sure where grasses get the "thirstiest" title from but acres of my course are native grasses as well as drought tolerant sedges, fescues, and a host of every kind of ground cover you can think of. I would think the benefits of an acre or grass versus a grove of trees would compare nicely re: photosynthetic benefits, erosion control.....
There is still a tone of apathy not so much in the industry but among club players about water. I was part of a small group that gave a water presentation with Mark Esoda at the AGCSA industry show a few years ago discussing how Georgia was/is reacting to our water issues and most of the attendees were from Australia
The general consensus then was marked by an answer to this question someone posed, "When do you think we can get golfers at the grass roots level to really understand and appreciate water issues in the industry?" The answer came from Mike Waldron, EX. Dir. for the GSGA when he said, "When someone turns the water off!"
Golf is certainly not perfect but we do have a far more positive story to tell about our environment and responsible use than we ever seem to get credit for. Supers in GA have done a phenomenal job reacting to the water crisis through their proactive BMP program and I am proud to see they are getting some recognition for it.