2012年-世界发展银行全球_Water_Resources_Trends_in_Middle_East_and_North_Africa_towards_2050_14页_3mb

Summary of Water Resources Trends in the Middle East and North Africa towards 2050

Core Content

This study explores the future trends of water resources in the Middle East and North Africa (MENA) region up to 2050, focusing on the interplay between climate change, population growth, and economic development. The research employs a two-stage modeling approach, combining a physically based hydrological model with a water allocation model to assess both water supply and demand.

Main Objectives

• To evaluate the impact of climate change, population growth, and economic development on water resources availability in the MENA region.
• To estimate future water demand and water shortages using integrated modeling and data sources.
• To address limitations of previous studies by incorporating a more comprehensive and detailed analysis.

Key Findings

Water Demand and Shortage Projections

• Total water demand in the MENA region is expected to increase to 393 km³ yr⁻¹ by 2050.
• Total water shortage is projected to reach 199 km³ yr⁻¹ by 2050, representing an increase of 157 km³ yr⁻¹.
• The increase in water shortage is attributed to a 50% rise in demand and a 12% decrease in supply.
• The uncertainty in projections is significant, with expected water shortages ranging from 85 km³ yr⁻¹ to 283 km³ yr⁻¹.
• 22% of the water shortage is due to climate change, while 78% is attributed to socioeconomic changes.

Water Availability and Scarcity

• The MENA region is the most water-scarce region in the world, with per capita water availability currently around 1076 m³ yr⁻¹, slightly above the physical scarcity limit.
• Country-specific variations are large, with some countries like Iran and Iraq having over 2000 m³ yr⁻¹ per capita, while others such as Jordan, Yemen, and many Gulf states have less than 200 m³ yr⁻¹.
• Surface water constitutes more than two-thirds of the total renewable water resources in the region.
• Rainfall is highly variable, with 65% of the region receiving less than 100 mm yr⁻¹, 15% receiving between 100–300 mm yr⁻¹, and 20% receiving more than 300 mm yr⁻¹.

Hydrological and Climate Trends

• Climate change is expected to increase temperatures and reduce precipitation, leading to higher evapotranspiration and reduced water availability.
• The Nile River is a key water source, with an average annual flow of 84 km³ yr⁻¹ at Aswan. However, there is uncertainty regarding the actual flows due to ongoing debates.
• Desalination is projected to increase water demand, but the study highlights the need for efficient water use and sustainable management.

Modeling Approach

• A hydrological model (PCR-GLOBWB) is used to simulate renewable water resources and climate impacts.
• The model is downscaled to 10 km spatial resolution and daily time step, which is a first for the entire MENA region.
• The water allocation model (MENA-WOF) is used to link water resources with sectoral demands, including agriculture, domestic, and industrial uses.
• The model integrates data from various sources, including remote sensing, GCMs, and socio-economic indicators.

Key Information

• Model Performance: The PCR-GLOBWB model shows good performance in simulating stream flows, with a high relative accuracy compared to observed data.
• Data Sources: The study uses high-resolution data including digital elevation models, vegetation maps, soil properties, irrigation data, population projections, and climate data.
• Socioeconomic Factors: Population growth and economic development are major drivers of increased water demand.
• GCMs and Downscaling: Nine GCMs are used to project climate change, and statistical downscaling is applied to refine the projections to daily and 10 km resolution.
• Water Use Priorities: The study includes return flows from irrigation, domestic, and industrial sectors, considering reuse and wastewater treatment.

Conclusion

The study underscores the increasing water scarcity in the MENA region due to climate change and socioeconomic factors. It highlights the necessity for integrated water management strategies and adaptation measures to address the growing water deficit. The use of advanced hydrological and allocation models provides a more accurate and comprehensive understanding of future water resource challenges in the region.