Steve,
Most sprinklers have a variety of nozzles and throw further at higher PSI. Most irrigation designers won't design for the biggest nozzle, furthest throw, just in case field conditions necessitate upsizing a few nozzles. Golf rotors can be designed to throw from about 50' - 90'. Flow ranges from 13-60GPM.
You might use 10 heads an acre at 89 ft. spacing, but 14 heads at or so (depending, as Don states on how you treat edges) so for 100 acres of turf, you can get by at 1000 heads or 1400 heads, depending on how strict you want to be on the DU, edge treatment, etc. Obviously, with the drive to water limits, and the cost of water, the industry has been pushing its more efficient sprinklers, tighter coverage, etc. I haven't figured it out in percentages like Don, but agree with them in general.
I guess I would do the math again, and see if the cost of 400 extra heads - which these days is over $1000 per head, or $400K pays off, or if the debt on that, about $32.5K will be more than your increased water cost. And, like Don says, in reality, that extra DU efficiency might never be realized. And, to be cynical to the DM level, if soil moisture is where its at, the irrigation companies will sell you all the soil moisture monitors you think you need.
Don,
So as far as I can tell, you as an irrigation designer and I as a golf course architect do push for similar things to keep costs in check. One year at GCBAA, I moderated an irrigation panel, and couldn't get any of those designers to admit in the slightest that you could lengthen water windows from the now standard 6 hours, water every other night reduce edge controls, etc., etc. etc. But the 70's style of accepting partial browning of less key areas (or even the fairways) has gone the way of the dodo bird in the mentality of most.
I have often made another calculation - they are afraid of closing their course even one day on the hottest August day of the year, because they may lose a day of revenue if they have to extend sprinkling several hours to catch the soil moisture up. If, on that hot day, they lose 50 rounds at $50, or $2500, they could lose up to 13 days of revenue, which would be less than the above $32K of debt, and it would be a balance at worst, and most years a plus.
It seemed to work for a long time, didn't it? It will probably be forced on us again, from the outside.
Sort of OT, but I also did a presentation with Bob Ferren of Pinehurst. While given the side of defending the modern "more heads" practice, vs his "water down the middle" I think my real argument would have been to take Pinehurst back to something like a 70-80's style (although I think they would have needed edge control) rather than all the way back to the 30's.
Maybe we are all influenced by what we saw when we grew up and I am getting old enough to be that club member who says "it was good enough in my day."
Your comment about tightening up tees and greens is spot on. I can recall more than a few instances where we moved tees back closer to the next green to save irrigation (and cart path). I wish there were more back and forth between irrigation design and golf. It should happen, but it doesn't as they usually are given the plans and irrigate to it. I do however, review those and adjust turf lines if I see that a 15-30 foot reduction ties to sprinklers better without affecting playability too much.
I guess my only question is, and I will ask around, is how many systems are really designed to the top end? I could be wrong, because of my client level, but I don't see a large portion of systems designed without some compromise and value engineering along the lines you propose.
Happy New Year.