The system performance curve is composed of a static and a dynamic component.
Hsystem = Hstat + Hloss(Q)
The static component Hstat is independent of the flow velocity (and thus of the flow rate). It contains the geodetic height difference as well as the pressure difference between suction and pressure vessel or inlet and outlet point of the system under consideration. In closed circuits (e.g. heating circulation) the static heed is always zero.
The dynamic part of the performance curve describes the piping losses, which depend on the flow rate. In the case of turbulent flow of NEWTON liquids with constant loss coefficients of the system components, the characteristic curve results in a square parabola. If the static head and the duty point are known, the system curve can be shown with sufficient accuracy.