For the first part of the project, I might hire an irrigation auditor. That should get you a technical efficiency for the current irrigation. You may need to put some work into evaluating the current water source(s) and past water usage, if they’ve kept records.
Regarding the new system:
Be careful with your water source. You may be able to harvest water from a parking lot, but if the water is salted, treatment will be prohibitive. Polluted water running through the irrigation system can ruin the entire course in a very short time.
Precipitation harvesting is a great idea where it’s legal. In Colorado for instance, watershed rights are not necessarily included in the land, and harvesting water can be a tricky proposition. If you can do it, I’d recommend running the water into a lined pond, and pumping water for irrigation from there. If precipitation water is short the pond can be augmented with other water sources. This also provides a buffer between supply and demand.
Many if not most modern golf course irrigation systems are centrally controlled from a computer that reads current weather conditions from a weather station on site. The system then puts down the amount of water lost the previous day through evapotranspiration.
An updated system will not only use less water, the improved water distribution can help reduce fertilizer requirements.
Speaking of fertilizing, a fertilizer injection system might be added to the new system allowing for fertilizer to be pumped into the irrigation system, giving very exact control of the amount of fertilizer being put down on the course. Many superintendants use this for soil conditioning instead of fertilizer though, since different amounts of fertilizer are put down in different areas of the course.
Another option to look into is a “links” style course which is much rougher, an limits the amount of irrigation required. Public perception may limit this possibility.
It will be a good idea to work closely with the superintendant of the course, after all, he will be the one having to work with and maintain whatever it is you end up designing.
If the owner has the money, now is a great time for updating the infrastructure on a golf course, costs are lower, and contractors are hungry!
Tim Grote - The Irrigation Engineers.