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• Board Meeting Date: 3/18/2008
• Description: IWMD Section - Presentation of Agricultural Water Conservation Paper
• Board Meetings - Doc Type: Memo

Section 4
Agricultural Conservation Measures
When evaluating agricultural water conservation improvements, it is important to
distinguish between practices that lead to improved application efficiency, as
opposed to reduced consumptive use. Water use efficiency is defined as the ratio of
water applied compared to water consumed by crop (i.e., ET.) Increasing efficiency is
likely to reduce losses from deep percolation and runoff (thereby altering historic
return flow patterns), but it may or may not materially affect the amount of water
consumed by the plant. Much of the water lost to these inefficiencies will return to the
river or groundwater system for use by downstream diverters. For this reason, the
law and customs in Colorado are clear that water
In certain situations, improved conserved due to water conservation practices that result
irrigation systems such as in improved efficiency is not available to the origi11a1
sprinklers and drip systems may appropriator for additional irrigation or other expanded
result in improved application uses.
uniformity over the entire field.
Consequently, areas that Examples of measures that increase efficiency include:
previously were under-irrigated
and where crop yields suffered ^ Ditch lining
now receive adequate water to ^ Pressurized pipe
meet full Crop ET. The net result ^ Conversion of flood irrigation to gated pipe, sprinklers,
may be increased crop or drip
consumptive use on a whole ^ Land leveling to increase irrigation uniformity
field basis and greater water ^ Furrow diking and contour farming
use. ^ Reduced tillage systems
^ Irrigation scheduling and monitoring
^ Tail water recovery
^ Polyacrylamide (PAM} use in ditches and furrows
The efficiency of various irrigation systems
vary. Flood irrigation normally ranges
from 30 to 50 percent efficiency. This
means that 30 to 50 percent of the water
diverted at the farm headgate is
consumptively used, while the remainder
is returned to the enviroiwtent via tail
water runoff, deep percolation, and
evaporation. Estimated efficiencies and
costs for various irrigation methods are
summarized in Table 4-1.
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DRAFT 4-1