Em4885 irrigation management practices to protect ground water

4 CHAPTER
IP 2.01.02 - Monitor Pumping Plant Efficiency
Objective
Maintain pressure and flow into an irrigation system as designed while maximizing energy
use efficiency. The distribution uniformity and thus, potential application efficiency, of
many irrigation systems are partially dependent on maintaining design flow and pressure
from the pumping plant.
Description
Many irrigation systems are partially dependent on a pumping plant maintaining the correct
water flow and pressure for good distribution uniformity. This is especially critical in
sprinkle and trickle systems. However, insufficient or fluctuating flows may also affect
furrow and border strip systems as well. If the pump performance should deteriorate this
could decrease the uniformity and efficiency of the system.
Pumping plants should always have a flow meter and a pressure gauge installed.
The grower should know the design operating condition of the pump, that is, the design
combination of flow and pressure. If the flow or pressure during operation are not as
designed then something may be wrong with the pumping plant. In the case of sprinkle or
trickle irrigation systems, the system may not be set up or being operated correctly, or
emission devices or nozzles may be worn or clogged.
Pacific Northwest Extension publication PNW285, Pumping Plant Efficiencies, discusses
how to test for pumping plant efficiency as well as providing tips on how to minimize
pressure losses in a system. Pumping plant efficiency tests may be available through
pump companies or private consultants.
During an efficiency test, the water horsepower output of the pump (a factor of the
combination of flow and total dynamic head) will be compared to the input horsepower.
Measurements that are needed include:
1. Well lift - pumping water level.
2. Well column losses.
3. Pump discharge pressure.
4. Pump flow.
5. Power into the pumping plant (either gallons per hour of fuel or kilowatt-hours).
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