I would imagine that a water gauge is the same as a catch cup, which is what the Rachio folks recommend for calibrating custom spray nozzles. This doesn't work for bubblers and emitters.
Many of us prefer to define custom nozzles from the flow rate as measured on your water meter feeding your property, if you have one. Divide that rate by the coverage area of your zone, and you have the perfect average nozzle definition. You can adjust for uneven coverage with the efficiency setting.