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Abstract
We approach the issue of water productivity in agriculture by identifying five sets of drivers of change. We find that irrigation efficiencies at the field level can result in real water savings under certain conditions, but that small farmers in most of South Asia and Africa have little incentive to adopt the appropriate measures. Although water productivity improvement and water savings at the regional level are possible through a shift to economically efficient crops, such changes may be constrained by concerns with respect to domestic and regional food security, rural employment, and farming system resilience.
Notes
1. These regions include the western United States, Mexico, the North China Plains, Indian and Pakistan Punjab, North Gujarat in India, Turkey, and Syria (Kumar & van Dam, Citation2009; Zwart & Bastiaanssen, Citation2004).
2. Substantial investments for on-farm water management systems, including water control devices, agronomic inputs and new crop technologies, are required to effect changes in yield and evapotranspiration (Barker et al., Citation2003).
3. Notable exceptions are Indian and Pakistan Punjab, where though water is scarce at the societal level, farmers are not confronted with the opportunity cost of using both canal water and groundwater. Also, they do not have extra land that can be brought under irrigation using the saved water.
4. This is because in many low-productivity regions water productivity improvements will result from supplementary irrigation and the resultant increase in consumptive use of water. Hence, WP improvements would be followed by increased water use per unit of land. However, under such a scenario, if we restrict the total irrigation-water delivery to such regions post-intervention to save water, we would still be able to maintain the agricultural output.
5. Field-level water savings refers to savings in water applied to the crop. Real water savings or “wet water savings” refers to reduction in water depleted. In the context of irrigation, this again can be at the plot level or at the level of the river basin (Seckler, Citation1996). Basin water use efficiency refers to the biomass output or economic return (INR) per volume of water depleted at the basin level, and improvement in the same can occur even when the amount of water depleted remains the same, provided that a greater proportion of it gets used up for beneficial transpiration (Molden et al., Citation2003). As regards water savings, even if there are real water savings at the plot level through agricultural water management interventions, if farmers expand the area under crop it would nullify the effect of plot-level water savings at the basin level.
6. This is unlike the western United States, Israel, Spain, South Africa and Australia, where water is priced volumetrically (Bruns et al., Citation2005; Haisman, Citation2005; OECD, Citation2011).
7. While major investments are required to achieve reduction in consumptive water use and yield enhancement, the incremental benefit to farmers would come only from higher yield and price per unit of output (Kumar & van Dam, Citation2009), which could be quite small compared to the investment. Kumar (Citation2007) illustrate this point using the case of drip irrigation for alfalfa in north Gujarat, India.
8. This refers to technologies which help water application in the agricultural field with high on-farm efficiency, characterized by minimum or zero field runoff and percolation and high distribution uniformity.
9. In India, for instance, the total government subsidy for installation of micro-irrigation systems released during the four year-period from 2007-08 to 2010-11 was only INR23.5 billion, or around USD435 million. This is too little when compared with the total area of 26 million ha that can be brought under MI systems (Institute for Resource Analysis and Policy [RAP], Citation2012).
10. By as early as 1998, the depth to the groundwater table in the Fuyang River basin, which forms part of the North China Plains, had fallen to 35 m, from just 8 m in 1974 (Wang & Huang, as cited in Henry, Citation2004).
11. WP (kg/m3) was estimated in relation to the sum of the irrigation water applied and green water use, and involved the assumption that the return flow from groundwater-irrigated fields is either retained by the vadose zone or eventually evaporates from the soil profile.
12. The marginal cost is much closer to the WP (INR/m3) values at the highest levels of irrigation.
13. The crop–livestock interactions were seen in the crop residues’ being used for animal feed. The extent of use of farmland for fodder was found to be highest for irrigated land under semi-arid conditions (Baltenweck et al., Citation2003, p. 44).
14. Studies from northern Victoria and southern New South Wales analyzed water use efficiency in dairy farms that are irrigated (Armstrong, Knee, Doyle, Pritchard, & Gyles, Citation2000), and dairy farming is not integrated with crop production in this region. Green fodder produced in irrigated grasslands is used to feed the cattle in Australia and the United States.
15. Here, in estimating overall net WP in crop and dairy production (INR/m3), only the irrigation component of the water used by the crops was considered. Though the rainfall contribution to ET for crop production is likely to be quite low in this region, with only 400 mm annual rainfall on average, this might have induced some error in the estimates of WP. But this should be acceptable given that we are concerned with comparative, not absolute values.