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Can water productivity improvements save us from global water scarcity?

  1. Can Water Productivity Improvements Save Us From Global Water Scarcity ? 25 February 2020 CIHEAM-Bari Winston Yu, Stefan Uhlenbrook, Rachel von Gnechten
  2. Numerous factors are contributing to increased global water scarcity. This raises concerns whether there will be enough water for all uses and particularly for food production. Water productivity interventions have been implemented in response to water scarcity. Assessing effectiveness is complicated by: • Multiple objectives (sometimes competing) • Multiple perspectives and scales • Terminology • Data and evidence
  3. Defining water use Consumption ApplicationWithdrawal
  4. Water productivity refers to the ratio of the benefits from agriculture systems to the amount of water used to produce those benefits Numerator or denominator term reflects water source (rainfed versus irrigated) “more crop per drop” Physical [kg/m3] Economic [USD/m3] Value derived per unit of water used Other
  5. Irrigation efficiency reflects the percentage of water used in irrigation Classical irrigation efficiency Water-use efficiency Effective irrigation efficiency
  6. Wide range of water productivity interventions, and not all directly address water scarcity Breeding and biotechnology practices Precision application practices Production practices Soil practices Water delivery practices Water management practices
  7. Water productivity interventions have different objectives at different scales and for different users
  8. Water productivity interventions are often branded for their water “savings” and improved irrigation “efficiencies” • “Efficiency” carries the implication that the “increase in efficiency actually saves some of the resource” (Jevon’s paradox) • Advanced irrigation technologies that increase ET can actually increase on-farm water consumption • Farmers switch to more water-intensive crops, expand production, or see “a strong marginal yield response from additional water” with the same crop (Grafton et al. 2018) • Irrigation efficiency paradox • Under what circumstances would real water “savings” still occur? • Food produced at a farmer’s increased irrigated scheme (enlarged through higher field irrigation efficiency) does not need to be produced elsewhere and, thus, water can be saved in a different basin.
  9. Water accounting terminology
  10. Many case studies reveal that water “savings” at the farmer-scale may not translate to water “savings” at the larger basin scale.
  11. Water Saving Technologies: Myths and Realities Revealed in Pakistan’s Rice-Wheat Systems (IWMI RR#108) Background • Objective: Assess the impact of “resource conservation” practices on water application, water productivity and real water savings • Location: Rechna Doab, semi-arid Punjab Province, Pakistan
  12. Ideally, the water received in the field would be used as transpiration to support crop growth. Some of these fluxes do not do this.
  13. Do these fluxes go to places that can be pumped or otherwise re-used by the same or downstream farmers OR do they go to degraded sinks?
  14. At field scale: Water application reduced At field scale adoption of resource conservation technologies led to • 24-32% reduction in water application at the field scale • Increased farm level incomes
  15. What does an increase in cropping intensity mean?
  16. At system scale: Water consumption increased Ahmad et al. 2007 Overall water consumption at the system scale increased by 59 million cubic meters/year following the adoption of “resource conservation” technologies.
  17. Reductions on water applications at the field scale translate into reduced water consumption in the system (i.e., farmers won’t use the “saved” water). Net farm incomes increased. Increased profitability incentivized farmers to expand cultivated area and/or increase cropping intensity. Belief Reality
  18. Topics to discuss during the workshop • Multiple objectives and motivations for adoption of different water technologies • “Improving water productivity is not a goal in and of itself” (Giordano et al. 2017) • Need to evaluate at the crop, field, farmer, basin, and regional scales • “There are rather few examples of carefully documented impacts of hi-tech irrigation” (Perry et al. 2017) • Need accepted, unambiguous terminology • Understand the (mis)conceptions of commonly used terms, such as water “savings” • What do “successful” interventions to deal with water scarcity depend on?
  19. Thank You