2012年-世界发展银行全球_The_Future_of_Water_in_African_Cities___Why_Waste_Water__Diagnostic_of_Urban_Water_Management_in_31_Cities_in_Africa_Companion_Volume_35页_2mb

Summary of "The Future of Water in African Cities: Why Waste Water?"

Core Content

This document presents a comparative analysis of urban water management in 31 cities across Sub-Saharan Africa, focusing on the challenges and capacities related to Integrated Urban Water Management (IUWM). The study is part of a broader initiative by the World Bank to better understand the water-related issues in African cities and to promote more sustainable and integrated approaches to water management.

Main Objectives and Aims

• To provide a comparative analysis of urban water management in 31 African cities.
• To identify the main challenges and capacities related to IUWM.
• To develop an index that evaluates how each city performs in different aspects of urban water systems.
• To support the development of sustainable and integrated water management strategies.

Methodology

The study employed a methodology inspired by the African Green City Index, developed by The Economist Intelligence Unit. It involved:

• Selection of cities: 31 cities were chosen based on population growth rate (>3%), population size (>2 million), and the presence of World Bank projects.
• Selection of variables and indicators: Six key variables were identified: urbanization challenge, solid waste management, water resources availability, water supply service, sanitation service, and flood hazard in river basins. For each variable, 16 indicators were selected, based on qualitative data.
• Definition and aggregation: Indicators were normalized and aggregated into a single score, with values classified into 5 intervals based on their deviation from the mean (±1.5xSD). The intervals were defined as:
  • 0: Well below average
  • 1: Below average
  • 2: Average
  • 3: Above average
  • 4: Well above average
• Data limitations: The study faced challenges due to inconsistent data definitions, limited availability of city-level data, and varying methodologies. Some data was self-reported, and there were inconsistencies in collection and measurement across cities.

Key Findings

Urbanization Challenge

• Rapid urbanization is a major challenge, with 20 out of 31 cities growing at more than 3% annually.
• Cities like Yaoundé, Kumasi, Luanda, and Abuja have growth rates exceeding 5%.
• Informal settlements are prevalent, with 7 cities having over 70% of their population living in informal areas.
• The average percentage of population in informal areas is 54.8%, with Luanda and Yaoundé being the highest at 80% and 75%, respectively.

Solid Waste Management

• The average solid waste collection rate is 51.7%, with 11 cities in the average category.
• Southern African cities, such as Cape Town, perform better with collection rates above 70%.
• Two cities, Mbuji-Mayi and Kano, have very low collection rates (20%).
• The average formal disposal rate is 55%, but there is significant variation across cities.

Water Resources Availability

• The average annual basin yield is 188 million cubic meters per year.
• 12 cities are located in basins with higher than average yields, while 5 cities are well below average.
• Douala has the highest basin yield at 1010 million cubic meters, while Khartoum has the lowest at 2.61 million cubic meters.
• The indicator has limitations, as it measures water generated within the basin rather than water available from external sources like the Nile.

Water Supply Service

• The average individual residential water consumption is 65.7 liters per capita per day, but 13 cities have consumption below 50 liters.
• Access to improved drinking water averages 65.6%, with Ibadan having the lowest at 22%.
• The average collection rate from billed populations is 42.2%, with Ibadan, Abuja, and Luanda underperforming.
• Revenue water averages 57.8%, with Khartoum and Dakar performing best, and Abuja and Kano worst.

Sanitation Service

• Access to improved sanitation averages 53.6%, with 12 cities below this average.
• Brazzaville, Dar es Salaam, and Lilongwe have the lowest access at 10.5%, 12.6%, and 14% respectively.
• Wastewater treatment levels are also low, with 41.7% or less treated in 8 cities.

Flood Hazard in River Basin

• Flood frequency is measured as the expected number of flood events per 100 years.
• 12 cities have an average of 9.9 flood events over 100 years.
• 10 cities are well above the average, with Kano and Khartoum having the highest at 25 and 21 events respectively.
• 9 cities have below-average flood exposure, with Johannesburg, Lusaka, and Harare at 2 events, and Cape Town, Lagos, and Luanda at 7 events.

Conclusions

• The study reveals that there is no clear "winner" among the cities, as all face significant challenges in urban water management.
• While some cities in Southern Africa perform better, they still encounter issues that require attention.
• The analysis highlights the need for integrated, flexible, and sustainable approaches to water management.
• The development of consistent, reliable, and high-quality city-level data is essential for future planning and monitoring.
• Institutional aspects of water management remain underexplored due to a lack of up-to-date and specific information.

References

• Bahri, A. (2012) Integrated Urban Water Management, TEC Background Papers, No.16, Global Water Partnership.
• Jacobsen, M. et al. (2012) The future of water in African Cities: why waste water?, Water Paper, The World Bank.
• The Economist Intelligence Unit (2011) African Green City Index: Assessing the environmental performance of Africa's Major Cities, Siemens: Germany.

Annexes

• Annex 1: Lists the variables and indicators used in the comparative analysis.
• Annex 2: Provides the methodology for calculating the index.
• Annex 3: Details the results of the comparative analysis for each variable.