Water Pump

At least tell us the color of the pump.

Actually that wont help much more detail is needed.

Is this the pump for fire fighting?

You should ask the supplier / manufacturer for detail and for your own convenience a pump curve. When you have a curve ask another question with all the detail and CR4 will put you on the fast lane.

you would need inlet outlet pressures, velocities, elevations, and friction loss. but that good ole' pump cuve is your starting point

Install an orifice plate or venturi meter that is sized for you capacity everything else is just more technology to manage and cry over when it quits. If you need a digital reading them attach a differential pressure sensor to your manometer so that it can remain in a constant state of calibration check for the absolute lowest cost and absolute best "ease of use".

The discharge of a fire fighting nozzle at a specific pressure can be calculated or can actually be obtained from a lookup table or curve.

Contact your supplier.