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404 | IAASTD Global Report
Table 6-3. Changes in water productivity (WP) by crop with adoption of sustainable agricultural technologies and practices in 144 projects.
Crops | WP before intervention | WP after intervention | WP gain | Increase inWP |
...................kg food m3 water ET-................ | % | |||
Irrigated Rice (n = 18) Cotton (n = 8) Rain-fed Cereals (n = 80) Legumes (n = 19) Roots and tubers (n = 14) |
1.03 (±0.52) 0.17 (±0.10) 0.47 (±0.51) 0.43 (±0.29) 2.79 (±2.72) |
1.19 (±0.49) 0.22 (±0.13) 0.80 (±0.81) 0.87 (±0.68) 5.79 (±4.04) |
0.16 (±0.16) 0.05 (±0.05) 0.33 (±0.45) 0.44 (±0.47) 3.00 (±2.43) |
15.5 29.4 70.2 102.3 107.5 |
Source: Pretty et al., 2006. |
proaches to water management, such as irrigation of partial root systems may hold promise for increasing production per unit of water transpired in specialized production systems (Davies et al., 2002). Besides crop and field practices, there is significant scope for reducing evaporation at the basin and landscape scales (Molden et al., 2007). High evaporation rates from high water tables and waterlogged areas can be reduced by drainage, or reducing water applications, after ensuring that these are not wetland areas supporting other ecosystem services. In degraded arid environments, up to 90% of rainfall evaporates back into the atmosphere with only 10% available for transpiration. Water harvesting in dry areas is an effective method of making available the non-beneficial evaporation of rainwater for crop transpiration (Oweis, 1999). Micro and macro-catchment techniques capture runoff and make it available for plants and livestock before evaporation, increasing the availability of beneficial rainwater, nearly halving evaporation and quadrupling increase in transpiration. Another option is to increase the use of marginal quality water for agricultural production. While marginal-quality waters, (wastewater, saline or sodic water), potentially represent a valuable source of water for agricultural production, long term environmental and health risks are significant and must be mitigated. The prevalence of and opportunities for increasing, the use of marginal quality water in agricultural production was recently assessed (Qadir et al., 2007). Public agencies in several countries already implement policies on marginal-quality water. Egypt plans to increase its official reuse of marginal-quality water from 10% in 2000 to about 17% by 2017 (Egypt MWRI, 2004). In Tunisia in 2003 about 43% of wastewater was used after treatment. Wastewater use will increase in India, as the proportion of freshwater in agricultural deliveries declines from 85% today to 77% by 2025, reflecting rising demand for freshwater in cities (India CWC, 2002). Worldwide, marginal-quality water will become an increasingly important component of agricultural water supplies, particularly in water-scarce countries (Abdel-Dayem, 1999). Water supply and water quality degradation are global concerns that will intensify with increasing water demand, the unexpected impacts of extreme events, and |
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climate change in resource-poor countries (Watson et al., 1998). State of the art systems to maximize use of saline drainage waters are currently under development in California and Australia (Figure 6-3) (Qadir et al., 2007). AKST development for sustainable use of marginal quality water is an urgent need for the future. 6.6.3.2 Multiple use livelihoods approach Livestock. Although there are few examples of research and assessments that attempt to understand the total water needs of livestock and how animal production affects water |
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