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-................ %
Rice (n = 18) Cotton (n = 8)
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


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. Multiple use livelihoods approach
Poverty reduction strategies entail elements primarily related to policy and institutional interventions to improve access for the poor to reliable, safe and affordable water. AKST contributes to increase the effectiveness agricultural water utilization by the poor. To secure water use rights now and in the future and to avoid or control the risks of unsustain­able water management, it is important to understand water as a larger "bundle of rights" (water access and withdrawal rights, operational rights, decision making rights) (Cremers et al., 2005; Castillo et al., 2007). Policy and institutional interventions are described in later chapters; here the focus is on AKST options that can contribute to poverty allevia­tion in the future, namely, multiple use system design, small scale water management technologies, and sustainable de­velopment of groundwater resources, primarily aimed at small scale farming systems in tropical countries.
        While most water use analysis focuses on crop pro­duction (particularly in irrigated systems), it is possible to increase the productivity of other components of mixed sys­tems to provide greater overall benefit for the rural poor (Molden et al., 2007), improve health for the local popula­tion and increase biodiversity. The design, development and management of water resources infrastructure from a mul­tiple use livelihoods perspective, can maximize the benefits per unit of water, and improve health. The integration of various water use sectors including crop, livestock, fisher­ies and biodiversity in infrastructure planning can result in increased overall productivity at the same level of water use, and can be compatible with improving health and maintain­ing biodiversity.

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