Altivar drive measures electrical power (from voltage and current) and considers the efficiency of the motor to give you result in form of mechanical power. Moreover, the power you enter in  Altivar drive configuration , which is also shown on motor plate is the nominal mechanical power on motor shaft. Nominal electrical power is determined by rated U, rated I and cos phi.
So power vs flow curve reflects mechanical power on motor (pump) shaft. It is not hydraulic power. If you check the pump datasheet published by pump manufacturers, the declared power is the power (mechanical) consumed by the pump.

Released for:Schneider Electric Egypt and North East Africa