Dear customer,

Thanks for your feedback and I will forward your sugestions to our R&D. Here are some typical flow rate: 
MISTER: 2 inch/hour
FIX_SPRAY_HEAD: 1.5 inch/hour
BUBBLER/ROTOR_HEAD: 1.0 inch/hour
ROTARY_NOZZLE: 0.7 inch/hour
ROTARY_EMITTER: 0.5 inch/hour

The reason why we use the area and depth flow rate(inch/hour) to calculate the water usage is that when the sprinkler system is professionally designed and installed, the zone is usually covered evenly, which means the large the zone is, the more sprinkler heads it needs. So the equation we use is 

Area(inch^2) x depth flow rate (inch/hour) x time (hour) = water usage(inch^3)

Another way of calculating the water usage is:

Number of heads x volume flow rate (inch^3 per head per hour) x time (hour) = water usage(inch^3)

You can see that the second equation uses the volume flow rate that needs to be provided by the user while the first equation uses the depth flow rate which can be largely determined by the sprinkler type. We actually had an internal debate on this and in the end we decided to go with the first equation because we want to reduce user inputs as much as possible to simplified the setup process. A

Again, thanks for the inputs and thanks for using Netro. 

Thanks,

Netro Support