2003年-世界发展银行全球_Prospects_for_Irrigated_Agriculture___Whether_Irrigated_Area_and_Irrigation_Water_Must_Increase_to_Meet_Food_Needs_in_the_Future_111页_867kb

Summary of "Prospects for Irrigated Agriculture"

Core Content

This report, prepared by the World Bank's Agriculture and Rural Development Department, evaluates the projections of future irrigation-water demand and supply by three international agencies: IWMI, FAO, and IFPRI. The goal is to validate these models and assess their implications for future food production and water resource management. The analysis focuses on the feasibility of increasing irrigated areas and water supply, the impact of policy interventions, and the role of technological and institutional improvements in addressing global water and food security challenges.

Main Objectives

• To evaluate the assumptions and scenarios used in global irrigation-water demand and supply projections.
• To assess the potential impacts of various policy interventions on irrigation-water demand and supply.
• To identify key areas for improving water-use efficiency (WUE) and addressing water scarcity.
• To provide insights for shaping the World Bank's Rural Development Strategy (RDS) related to water and food security.

Key Findings from Existing Forecasts

1. IwMI Projections:

   • The world's primary water supply would need to increase by 28% by 2025, from 2,120 km³ in 1995 to 2,718 km³.
   • This increase would be necessary to support irrigation in a growing population, with the potential to release 600 km³ of water over a 30-year period through improved storage.

2. FAO Projections:

   • Agricultural-water demand should not exceed available water resources, based on renewable water sources.
   • In arid countries, irrigation areas often exceed irrigation potential due to the use of fossil groundwater.
   • Water balance is expressed in yearly averages, which may not reflect seasonal or interannual variations.

3. IFPRI Projections:

   • Scenarios with low investment in irrigation show a significant reduction in water availability and reliability by 2025.
   • These scenarios lead to a decline in irrigated area and food production, with the most severe impacts in developing countries.
   • High municipal and industrial water demand further reduces irrigation-water availability.

Emerging Issues and Expert Opinions

Experts identified several critical issues that require attention:

• The extent to which improving WUE at both field and basin levels can reduce future water demand.
• The role of demand-based approaches, such as full pricing of irrigation water and internalizing externalities, in closing the supply-demand gap.
• The impact of intersectoral water demand and pricing policies on irrigation-water availability.
• The importance of transboundary water management and water trading for sustainable and cost-effective resource allocation.
• The feasibility of large reservoir storage to meet growing water demand, including its financial, economic, social, and environmental implications.
• The need to estimate costs and financing feasibility for water-related projects.
• The significance of water-harvesting techniques and rain-fed agriculture in reducing pressure on irrigation systems and water resources.
• The importance of environmental considerations in water demand and supply models.

Revised Scenarios and Findings

1. Improved WUE:

   • Enhanced water-use efficiency could significantly reduce global irrigation-water consumption.
   • Efforts should focus on basin-wide efficiency rather than only field-level improvements.
   • WUE improvements are particularly crucial in water-scarce regions such as the Near East, North Africa, and southern Asia.

2. High Water Prices:

   • Scenarios with higher water prices showed a large reduction in water withdrawal, higher basin efficiency, and full water reservation for the environment.
   • These scenarios had modest impacts on food production, as price response is low in agriculture.
   • Policy integration at the sectoral and economy-wide level is essential for promoting efficient water use and achieving MDGs.

3. Technological Improvements:

   • Technology plays a key role in improving WUE, raising water productivity, and solving future water scarcity.
   • Research on drought-tolerant crop varieties is important for addressing the challenges in arid and semi-arid areas.

4. Intersectoral Water Demand:

   • Increased domestic and industrial water demand can limit irrigation-water availability.
   • However, reforms in water-pricing policies may increase irrigation-water availability due to the prioritization of non-irrigation uses.

5. Rain-fed Agriculture:

   • Improvements in rain-fed agriculture could offset the need for conventional water augmentation.
   • Water-harvesting techniques and effective rainfall management can significantly reduce groundwater overdraft.
   • There is a need to broaden the scope of irrigation-water investment programs to include these techniques.

6. Environmental Factors:

   • Environmental considerations are important but limited by a lack of data.
   • Efforts should be made to improve environmental databases and make farmers aware of adaptation processes to climate change.

7. Institutional Aspects:

   • Institutional limitations, such as water rights and capacity building, affect the performance of irrigation projects.
   • Institutional reforms and economic instruments are important for improving WUE and reducing total irrigation demand.

Implications for the World Bank Rural Development Strategy

• The validation exercise provides clear insights into the implications of improvements in crop genetics, WUE, and the shift in investments to rain-fed areas.
• The RDS should prioritize basin-wide efficiency, WUE improvements, and rain-fed agriculture.
• Policy integration at the sectoral and economy-wide level is essential for promoting efficient use of water and achieving food and water security.
• There is a need to consider a broader range of scenarios and assumptions, including the potential for rainwater harvesting, water recycling, and climate change adaptation.

Conclusion

The report concludes that improved water-use efficiency, technological advancements, and policy integration are key to addressing future water and food security challenges. The validation exercise highlights the importance of incorporating multiplier effects, intersectoral demand, and institutional reforms into future projections and strategies. The World Bank should leverage these findings to shape its rural development strategy, focusing on sustainable and efficient water use.