Pumps & groundwater


Where am I on the PUMP CURVE?


— By Len Ring, MSc, PE, CID —


Pumping station using VFD-controlled pump motors in the Western Irrigation District, Alberta, Canada


SPEED, EFFICIENCY & ENERGY CONSUMPTION P


umps often provide the flow (gallons per minute) and pressure (pounds per square inch) or head (feet) to match an irrigation system design. If selected well, they provide that flow and head efficiently. If one pump


is used, one pump curve will indicate the flow and head that can be expected. With multiple pumps, a combination pump curve can be developed for the pumps in parallel or series as necessary. When referring to a pump curve in this article, it is referring to the single pump or combination pump curve, whichever


applies. The pump curves shown (pg. 12) are derived from an actual manufacturer’s pump curves, revised using the affinity laws.


System curves & pump curves System curves show how an irrigation system flow increases as the input pressure increases. Pump curves show how the head developed decreases as the flow increases. The pump and system operate at the point where the two curves cross. This is a key concept in order to know where we are on the pump curve.


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