Explain the relationship between pump curve and system curve.

The pump curve (H vs Q) shows head developed at various flows - it decreases as flow increases for centrifugal pumps. The system curve shows head required by the piping system - it increases with flow squared due to friction. The operating point is where curves intersect. System curve shifts up with increased resistance (valve closure, fouling); pump curve shifts with speed changes or impeller trimming. Understanding this interaction is crucial for pump selection and troubleshooting flow problems.