30 ‎(3)‎

• Board Meeting Date: 5/21/2008
• 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 f low patterns), but it may or may not materially of f ect the amount of water
consumed by the plant. Much of the water lost to these inefficiencies will return to the
river or groundwater system f or use by downstream diverters. For this reason, the
In certain situations, improved
irrigation systems such as
sprinklers and drip systems may
result in improved application
uniformity over the entire field.
law and customs in Colorado are clear that water
conserved due to water conservation practices that result
in improved efficiency is not available to the original
appropriator f or additional irrigation or other expanded
uses.
Consequently, areas that Examples of measures that increase efficiency include:
previouslywereunder-irrigated
and where crop yields suffered
now receive adequate water to
meet full crop ET. The net result
may be increased crop
consumptive use on a whole
field basis and greater water
use.
^ Ditch lining
^ Pressurized pipe
^ Conversion of flood irrigation to gated pipe, sprinklers,
or drip
^ Land leveling to increase irrigation unif ormity
^ Furrow diking and contour f arming
^ 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 f arm headgate is
consumptively used, while the remainder
is returned to the environment 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