As energy costs have risen in recent years, sprinkler
irrigation equipment has been designed to apply water at
lower pressures. Some low pressure devices have been
developed for use with set-move systems, but the most
popular application has been on self-propelled systems
such as center-pivot and linearmove systems.
Although low pressure sprinkler systems reduce irrigation
pumping energy requirements in most cases, their
use can greatly increase the potential for runoff. Since
the pattern diameter of low pressure sprinklers is less
than that of high pressure sprinklers, water is applied
over a smaller area. This increases the application rate,
and can often exceed the soil water intake rate. (These
relationships are explained in the BPA Irrigation Energy
Efficiency sheet on "Irrigation Runoff Control Strategies.")
If the water application rate exceeds the intake rate,
surface ponding can occur. This surface water can move
within the field from high areas to low areas. Runoff or
wet and dry areas provide visual evidence of surface
water movement, which results in crop variability and loss
in crop production. These losses can be reduced by
increasing intake rates and/or surface storage capacity of
the soil so that all water is retained where it is applied
