Importance
of Irrigation Water Management in the GWPA Regulations
Irrigation water management (IWM) plays an important role
in the GWPA regulations when one of the 6800(a) pesticides
is to be applied in a Leaching GWPA. One of the important
leaching GWPA mitigation measures is to apply no more
than 1.33 times the net irrigation requirement at each
irrigation for 6 months following the pesticide application.
Optimizing the irrigation system performance and management
may be required to comply with this requirement.
Purpose of Irrigation
Irrigation is the process of supplying water, in addition
to natural precipitation, to field crops, orchards,
vineyards, or other cultivated plants. Irrigation water
is applied to ensure that the water available in the
soil is sufficient to meet crop water needs. The role
of irrigation is to improve production and the effectiveness
of other inputs.
Overall, irrigation water is applied to maintain a
favorable water balance in the crop root zone, but,
in order to maintain this balance, an excess of water
is applied resulting in some water becoming deep percolation
(water that passes vertically through the root zone
to deeper soil layers below the crop root zone) or surface
runoff (applied water that does not enter the soil and
flows off the lower portion of a field). Both deep percolation
and surface runoff are not available for use by the
crop, although in some areas, deep percolation and surface
runoff can play a vital role by helping to leach salts
from the crop root zone, for cooling and frost protection,
and for groundwater recharge.
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Irrigation
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