An artificial lift system has a surface pump operated by a prime mover powered by a variable speed drive. A jet pump disposed downhole in tubing receives pressurized power fluid from the surface pump, mixes the power and production fluid and delivers the product uphole. A controller disposed at surface adjusts the artificial lift system relative to a set value based on a measured discharged pressure or a measured flowrate and trends a change in the other of the measured flowrate or the measured discharged pressure over time. The controller can also trend an operating condition (intake pressure vs. production rate) to determine changes relative to cavitation conditions. Based on the trended changes, the controller initiates an operation in the artificial lift system, such as adjusting the discharge pressure, initiating an alarm condition, etc.