Jacob Burke

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Water Efficiency and Groundwater Does it
matter?

• Jacob Burke
• Senior Water Policy Officer
• Agriculture Department, Food and Agriculture
  Organization of the UN

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CA Chapter 9 Statement

• Water saving and water use efficiency in
  irrigation
• The concept of water use efficiency (the ratio
  between effective water consumption by crops and
  water abstracted from its source for irrigation)
  is subject to controversy and
• misinterpretation. Developed initially for use in
  the design of physical structures of water
  storage and conveyance in irrigation systems
  (Israelsen 1932), the concept was later
• interpreted as a measure of irrigation
  inefficiency and waste because only 3050 of
  the water withdrawn from its source is actually
  transpired by crops in a typical irrigation
  system, many conclude that substantial gains in
  water volumes can be obtained by increasing water
  use efficiency in irrigation.

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Basic Definitions (Smith, 2001)
conveyance efficiency (iec), farm efficiency
(ief) and field application efficiency (iea)
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Classical Irrigation Efficiency

• CA (2006)
• The ratio between effective water consumption by
• crops and water abstracted from its source for
  irrigation)
• Lankford (2006)
• Classical irrigation efficiency (CIE), defined by
  the International Commission on Irrigation and
  Drainage (ICID, 1978) as a ratio of average depth
  of water beneficially used to average depth of
  water applied, while Bhuiyan (1982) defined
  irrigation efficiency as a ratio of net
  irrigation requirement to the supply. Using these
  and other similar computations, efficiency of
  surface irrigation is held to be around 40

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Effective Irrigation Efficiency

• include (s) assessment of water that is
  potentially available for reuse downstream,
  arguing that in river basins where drainage
  waters are reused, a water multiplier effect
  results in high irrigation efficiency when
  assessed at basin level.
• Lankford (2006)

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Attainable Irrigation Efficiency

• Attainable efficiency is based on the concept
  that some losses (which may be recovered or
  non-recovered) can easily be reduced, while
  others cannot unless considerable effort is
  expended.
• Thus, evaporation from canals during
  conveyance is unavoidable but evaporation
  occurring from a long period of presaturation
  wetting of a rice field is avoidable and
  manageable. Attainable efficiency is the result
  of dividing low dose irrigation by high
  dose irrigation.
• AIE low dose irrigation/high dose irrigation

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The Lankford Scheme (2006)
9
The Ground Water Issue Lankford (2006) footnote

• One of the World Banks Chief advisers on water,
  Stephen Foster of the British Geological Survey,
  is horrified by the idea that making irrigation
  more efficient will free water for other uses.
  It has the makings of a very dangerous myth,
  he says. There is, he adds, a horrible flaw in
  the argument. Most of the water being saved is
  never truly wasted in the first place. Some, it
  is true, is lost to evaporation. But mostthe
  water that seeps underground from fields and
  canalseventually finds its way to natures
  underground water reservoirs, from which millions
  of farmers subsequently pump water to supplement
  river water for irrigation. The Independent
  (UK), The Great Water Myth by Fred Pearce, 28
  Jan 2004.

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North China Plain Research

• By considering the entire hydrologic system,
• including both the soil profile and the
  underlying
• aquifer, we found that evapotranspiration is the
• only water actually depleted from the system.
• The only way to save water is to reduce
• evapotranspiration, which can be accomplished
• by reducing the cropped area. Thus, an
• eventual shift from irrigation to other, less
• consumptive water uses must play a crucial role
• in any long-term solution to water-table
  declines.
• Eloise Kendy et al 2003 IWMI Research Report 71

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