I thought I would share a little data based on my experience in my lawn. My overall lot is 1 acre, however only approximately half of that (say 22ksqft) needs irrigation.
Here are my actual values from my lawn based on measuring Pr using the method of putting collection cups in the zones and running them for 15m. I spent about 4 hours in the lawn, putting down a set of shallow plastic containers with straight sides, flat bottoms, with a heavy rock in each one to keep them from blowing away or moving around. What I found was eye-opening.
zone#: type – Pr – comment
1-4: spray heads – 1.5in/hr – spray head coverage for me was extremely uniform, with +/- 10%
5: 5x rotors – 0.56in/hr – well designed zone, with excellent overlapping, heads laid out in a triangle formation right out of the literature!
6: combination zone, with 3 rotors and 5 spray heads – terrible zone to manage, rotors got .35in/hr coverage, spray heads were 1.47in/hr
7: 4x rotors – 0.41in/hr, partially overlaps zone 6 (!!!)
8: 6x rotors – 0.5in/hr
9: 5x rotors – 0.275in/hr – almost no overlap between rotors in the zone
10: 4x rotors – 0.53in/hr
11: 3x rotors – 0.4in/hr – where there was coverage, there was a portion of this zone without any coverage at all (0!) due to a driveway extension by a previous homeowner taking out a head (or 2?)
12: 5x rotors – 0.475in/hr
13: 5x rotors – 0.25in/hr – very sparsely covered zone, with almost no overlap between rotors
14: 4x rotors – 0.45in/hr
15: spray heads+drip – 1.53in/hr for sprayers, drip heads are 2gpm put into 2 tall decorative pots with lemon trees
16: 4x rotors – 0.35in/hr – 16 overlaps the half of 17s coverage area, unclear why that was done
17: 4x rotors – 0.475in/hr – fully overlapped by 16 & 18 coverage, 2 heads were relocated during a rear patio expansion which caused the overlap with 18
18: 4x rotors – 0.375in/hr – overlaps the other half of 17s coverage area
All this got me to believe that I couldn’t calculate coverage based on types of heads in software. Given what I see in my area, most lawn sprinkler setups are similar, with very poor overall design and impacts being made by landscape or hardscape changes.
Here in Texas, my water costs run about $50/month during the winter when I’m not running my sprinklers, but during the summer, there have been $300/month bills multiple times in the last few years. All this leads me to have a strong financial incentive to be more optimal in my water use on top of my overall desire simply not to waste water.