The pump should last a long time but, if the new pump specifications are known, then one has information to use to check the pump performance in the future. The initial pressure and flow information can be verified to see if it still exists. Variations from the initial conditions may be due to wear in the pump or in the nozzles. If the flow has increased, then nozzle wear may be an issue. The pressure may decrease if the pump must provide more flow. The pump performs according to its design characteristics that are shown in a pump chart which shows water pressure versus water discharge.
Changes in the irrigation system are more likely to be the cause of changes in the pressure and flow conditions of the system. One should check to see the correct operating pressure is available in the system. If not, then some change to the system may be causing the problem.
Well yield and draw down
During drought conditions there may be a serious shortage of water and the depth of water in a well may change with use if the inflow of water to the well is decreased. If system pressure or flow rate has decreased and a well is being used, then a qualified person or company should check on the well yield.