Pressure is usually measured in...

Pressure is typically measured in psi, which stands for pounds per square inch. This unit quantifies the amount of force exerted by a fluid per unit area, making it a common measurement in various fields, including engineering, hydraulics, and water management. Knowing how to measure pressure accurately is crucial for ensuring proper system functionality and safety when working with surface water systems.

The other options represent different measurements: cfs (cubic feet per second) is a unit of flow rate, gpm (gallons per minute) also measures flow rate, and fps (feet per second) typically measures velocity. While all of these units are important in the context of water management, they do not assess pressure. Thus, psi is unequivocally the correct choice for measuring pressure specifically.