2016年-世界发展银行全球_A_Preliminary_Investigation_of_the_Potential_Costs_and_Benefits_of_Rehabilitation_of_the_Nakivubo_Wetland_Kampala_107页_5mb

Summary of the Nakivubo Wetland Rehabilitation Study

Core Content

This document presents a preliminary investigation into the potential costs and benefits of rehabilitating the Nakivubo wetland in Kampala, Uganda, as part of a broader study on Green Urban Development in African cities. The study was commissioned by the World Bank and led by AECOM, with Anchor Environmental Consultants and Freshwater Consulting Group conducting the analysis. The focus is on understanding the ecological and economic value of the wetland and assessing the feasibility of its restoration.

Main Objectives

The primary objectives of the Nakivubo wetland rehabilitation study include:

• Improving water quality in the wetland and Inner Murchison Bay
• Ensuring sustainable management of the wetland
• Reducing water quality impacts on human health
• Enabling safe recreational use of the lower wetland

Key Interventions

A sequential set of interventions, referred to as a "treatment train," was recommended to achieve these objectives:

1. Prevent pollution at source through improved sanitation infrastructure.
2. Prevent residual pollution from entering the wetland.
3. Improve effluent quality from Waste Water Treatment Works (WWTW).
4. Rehabilitate the upper wetland for secondary waste water treatment / polishing.
5. Restore and protect the lower wetland.
6. Establish recreational space and facilities.

These interventions involve both infrastructure upgrades and wetland conservation efforts.

Key Findings

• The Nakivubo wetland has become severely degraded due to pollution, reclamation for agriculture, and encroachment by human settlements.
• The wetland no longer provides any positive ecological impact on Inner Murchison Bay, which has reached a hypertrophic state with frequent algal blooms and pathogen contamination.
• The wetland was previously providing significant cost savings to the Ggaba Water Treatment Works by reducing the need for chemical treatment.
• The total estimated capital cost for rehabilitation is $53 million, with ongoing maintenance and operating costs of $3.6 million per year.
• The cost of forgone agricultural production in the wetland area is estimated at $141,500 per year.
• The net present value (NPV) of the project over 15 years is $80 million at a 6% discount rate.
• The internal rate of return (IRR) is estimated at 20%, with a sensitivity range of 4–34%.
• The recreational benefits are estimated to be $22.05 million per year, based on survey-based methods.
• A reduction in phosphorous concentrations could save $1.143 million per year in water treatment costs.

Key Messages

1. Wetlands have limited capacity to solve urban pollution problems.
   The Nakivubo wetland can no longer provide significant water treatment benefits, and its restoration cannot substitute for wastewater treatment works.

2. Rehabilitation will be costly but worthwhile.
   While the investment may not be cost-effective on its own, the combination of water treatment savings and recreational benefits makes it a viable option.

3. There are no shortcuts.
   All interventions must be implemented to ensure the success of the rehabilitation. The order of implementation is less important than ensuring all steps are carried out.

4. This will require fundraising and co-ordination.
   The project may only be feasible with donor funding, and coordination between multiple institutions is essential for effective implementation.

5. Avoid a repeat experience.
   Delays in investment can lead to irreversible environmental and economic damage. Proactive management is crucial to prevent further degradation of the wetland and surrounding areas.

Policy Recommendations

• Sanitation measures must keep pace with urban population growth.
• Water quality standards for wastewater treatment should be increased and enforced.
• Stricter regulation and control of industrial discharges are needed.
• Legal protection of wetlands should be strengthened to prevent reclamation, farming, and settlement.
• Construction of roads and railways through wetlands should be avoided or minimised.
• Monitoring programs should be established, including continuous flow and monthly water quality measurements, and data should be made publicly available.

Conclusion

The study highlights the importance of integrating green urban development with environmental protection and public health. It underscores the need for a coordinated, multi-institutional approach to wetland rehabilitation and the potential for significant economic and ecological benefits, particularly in a rapidly growing city like Kampala.