2014年-世界发展银行全球_Understanding_the_Impact_of_Climate_Change_on_Hydropower___The_Case_of_Cameroon_166页_7mb

Summary of "Understanding the Impact of Climate Change on Hydropower: the case of Cameroon"

Core Content

This report, conducted by Johan Grijsen for the Africa Energy Unit (AFTEG) of the World Bank, assesses the impact of climate change on hydropower generation in Cameroon, focusing on five main river basins: Sanaga, Benue, Nyong, Ntem, and Niger. The study uses a risk-based approach and climate elasticity to evaluate how changes in precipitation, temperature, and potential evapotranspiration affect water availability and hydropower output. The findings aim to support development planning and the operation of hydropower infrastructure, particularly the Lom Pangar and Nachtigal projects.

Main Objectives

• To evaluate the potential impacts of climate change on water resources availability for hydropower generation in Cameroon.
• To assess the climate resilience of existing and planned hydropower infrastructure.
• To support the Electricity Development Corporation (EDC) in making informed decisions for the Lom Pangar and Nachtigal projects.
• To provide a risk-based methodology for future investments in hydropower and water resources.

Key Findings

1. Climate Resilience of Key Projects

• Lom Pangar and Nachtigal projects in the Sanaga Basin are economically robust and climate resilient.
  • Annual hydro-energy generation could vary between -15% and +5% by 2050, and -15% and +5% by 2080.
  • The EIRR (Economic Internal Rate of Return) for these projects is not sensitive to moderate runoff changes (less than 20%).
  • Only if runoff decreases by more than 20%, the EIRR could be affected significantly, with a maximum reduction of about 10%.
• Lagdo Dam in the Benue Basin is less climate resilient:
  • By 2050, there is a 20% probability that annual hydro-energy generation could decrease by 20% or more.
  • By 2080, this probability increases to 30%.
  • The EIRR of Lagdo is expected to decrease significantly, which could affect its long-term viability.

2. Runoff Elasticity and Climate Sensitivity

• The runoff elasticity of hydro-energy generation varies across basins:
  • Sanaga Basin: Runoff elasticity of 0.7 (base case), improving to 0.5 with the Lom Pangar reservoir.
  • Benue Basin: Runoff elasticity of 0.8 to 1.0, with a higher sensitivity to climate changes.
  • Nyong and Ntem Basins: Runoff elasticity of 1.0 for guaranteed monthly output, with minor to moderate climate impacts.
• The aridity index and runoff coefficient show that the Benue Basin is more vulnerable to climate change due to lower rainfall and higher temperatures.

3. Climate Projections

• Precipitation:
  • No significant changes are projected by 2050 (A1B emission scenario), with a standard deviation of 7%.
  • A small increase of 4% is projected by 2080, with a standard deviation of 11%.
• Temperature:
  • An average increase of 2.0°C by 2050, and 3.0°C by 2080.
  • Potential evapotranspiration increases by 4–5% with a 2°C temperature rise.
• Runoff Projections:
  • A small decrease of 4% in average annual runoff by 2050.
  • A potential decrease of up to 35% by 2080.
  • The spread of projections is significant, with standard deviations of 17% by 2050 and 24% by 2080.

Methodology

• A bottom-up, risk-based approach was used to assess climate impacts on hydropower.
• Climate elasticity was calculated to quantify the sensitivity of hydro-energy generation and EIRR to changes in runoff.
• Decision scaling was employed to estimate the likelihood of climate-induced hazards.
• An ensemble of 15 climate projections from GCMs (Global Circulation Models) was used to capture the range of possible future climate conditions.
• Seasonal and annual hydro-energy models were developed using Excel, based on historical monthly runoff data (1971–2003) and climate projections.

Recommendations

• Use worst-case climate scenarios for impact analysis:
  • 2050: 15% reduction in precipitation (25% probability), 35% reduction (3% probability), and 10% increase (20% probability).
  • 2080: 20% reduction in precipitation (100% probability), 30% reduction (5% probability), and 30% increase (2% probability).
• Re-evaluate the installed capacity of the future Nachtigal power station to account for potential increases in runoff.
• Conduct robust decision analysis for infrastructure projects with long lifetimes to address uncertainties and vulnerabilities.
• Emphasize anticipatory adaptation for projects that are irreversible or inflexible.
• Use multi-model ensembling to reduce model uncertainty and natural variability in climate projections.

Conclusion

The study concludes that Lom Pangar and Nachtigal projects are climate resilient and economically robust, while Lagdo Dam is more vulnerable to climate change. The Sanaga, Nyong, and Ntem basins are expected to experience minor to moderate climate impacts. Robust decision-making and anticipatory adaptation are essential to manage the long-term risks associated with climate change for hydropower and water resources in Cameroon.