Technical Concepts Related to Conservation of Irrigation and Rainwater in Agricultural Systems
ITRC Report No.
A.J. Clemmens, R.G. Allen, and C.M. Burt
Water Resources Research, Vol. 44, W00E03, doi: 10.1029/2007WR006095, 2008. To view the published open abstract, go to http://dx.doi.org and enter the DOI.
Forty percent of freshwater withdrawals in the
United States are for irrigated agriculture, which contribute
more than $50 billion to the economy. Increasing
diversions of water for urban, environmental, and other uses
will likely decrease water available to agriculture. Water
conservation in agriculture is touted as a good method for
minimizing the impact of reduced agricultural diversions on
production. Because "wasted" water is often reused until
it reaches the ocean, there are limitations to the ture water
savings that result from programs that aim to increase
irrigation efficiency. True water savings can come from
four areas: reduction of unnecessary evaporation and
transpiration, more effective use of rainfall, reduction of deep
percolation water that becomes severely degraded in quality, and
reduction of runoff from fields that is not reusable downstream.
Any other reduction in net water consumption must come from
reduction in evapotraspiration from the crops grown, which
requires either reduction in acreage or reduction in crop yield
brought on by intentional plant water stress. Other
benefits of field or district-level water conservation may
include increased in-stream flows (due to lower diversions) and
energy conservation due to less pumping or more hydroelectric
production, but not result in true water savings, since
unconsumed water returns as a usable water resource.
Understanding the hydrologic settings is critical to determining
true water savings from conservation practices. On-farm
water conservation practices that provide true water savings at
one location may be ineffective at another. In large
irrigation projects, water delivery limitations often present
obstacles to on-farm water conservation efforts.
An edited version of this paper was published by AGU. Copyright 2008 American Geophysical Union.
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