Recruiting top notch employees is easier with top notch infrastructure. Flowmeters open and close an electric contact each time a certain volume of water flows through them. By counting the contact closures, water use is tracked. Flow rates and volumes may be monitored. Cumulative flow and run times are helpful for scheduling pump and filter maintenance.
Larger meters have more flow per contact closure than small meters.
For instance, a 1 inch meter may close every gallon, while a 3 inch meter may close every 100 gallons. In an ideal system, meters would be located at each valve. However, irrigation research is about the only application that can justify such an expense. Each water source used for irrigation should have a meter. Multiple meters on the same source are cost effective if lots of concurrent irrigation in different locations is the norm.