The expansion of large-scale hydroelectric power projects in temperate regions has brought the need for greater understanding of GHG emission patterns and dynamics across varying climatic and ecological settings.
These issues are described as being more pronounced in South Korea, where hydropower supports national energy security, but empirical GHG datasets are sparse. As Min et al explain in Renewable and Sustainable Energy Reviews, the country still relies on IPCC Tier 1 wetland factors to inventory reservoir emissions, a practice they say overlooks domestic watershed characteristics and anthropogenic nutrient inputs.
In recent years, efforts by UNESCO and the International Hydropower Association have led to greater accuracy with the development of the GHG Reservoir (G-res) Tool. Although recent G-res Tool applications span China, Europe, North America and Vietnam, the authors claim multipurpose dam reservoirs in temperate East Asia remain underexamined.
To address this, the authors used the G-res Tool to assess GHG emissions and carbon footprints from seven multipurpose dam reservoirs located in temperate regions of South Korea, where empirical studies on reservoir-related emissions remain limited.
The Korea Water Resources Corporation manages the construction and operation of 21 multipurpose dams across the region. This study focused on seven dams that were selected based on their high rankings of hydroelectric power generation capacity and reservoir surface area. These were:
- Soyang and Chungju in the Han River Basin.
- Andong, Imha, and Hapcheon in the Nakdong River Basin.
- Daecheong and Yongdam in the Geum River Basin.
South Korea has a temperate monsoon climate, with approximately 60–70 % of its annual precipitation falling during the summer monsoon and typhoon. This highly seasonal rainfall causes pronounced fluctuations in reservoir water levels and thermal stratification, affecting GHG emission dynamics. These three major river basins exhibit distinct geological and hydrological characteristics that may influence GHG emissions.
The results found that all systems acted as carbon sinks before impoundment but became net emitters after dam construction. The Daecheong reservoir had the highest net GHG emissions, mainly due to significant forest cover loss before impoundment. After reservoir construction, emissions were primarily attributed to surface CO2 diffusion, followed sequentially by CH4 diffusion, degassing, and bubbling. Higher total phosphorus concentrations are strongly linked to increased emissions, suggesting that improving water quality can help reduce emissions.
The authors say their results underscore the importance of linking reservoir GHG assessments with land-use planning and water quality control. The study provides practical guidance for dam managers and policymakers seeking to improve operational performance while minimising climate impacts through integrated upstream-downstream management strategies.
Potential in Rwanda
Rwanda is a rapidly growing country and ranks among the fastest-electrifying countries in Sub-Saharan Africa. With agriculture accounting for a quarter of national GDP, improving productivity is essential due to limited opportunities for expansion of cultivated land.
Access to clean drinking water is another challenge the country faces. According to UNICEF, just 57% of the population has access to clean drinking water within a 30-minute distance from their homes.
Expanding access to both electricity and clean drinking water remains a central developmental challenge and recent research has focused on a case study in the Eastern Province’s Tabagwe to address this.
The investigation looked at the feasibility of implementing a multipurpose dam system to support irrigation while simultaneously enabling electricity generation and water purification through an integrated infrastructure. A linear optimisation model was developed to identify the most cost-effective setup of this multipurpose dam.
The result showed that a multipurpose dam providing irrigation, electricity, and clean water could be a viable solution for Tabagwe. These functions can be adapted to local needs and economic conditions. The most advanced configuration offered electricity access of 1kWh capacity, available for at least eight hours per day, sufficient to power appliances such as a refrigerator, fan, or television.
Optimisation of multipurpose projects
The problem of parallel and series use of multiple and multipurpose reservoirs in the dams of Iran’s Karun watershed has been the focal point of a recent study. Optimising the operations of dam reservoirs with the objective function of minimising shortages and maximising hydropower production was modelled
and solved using training data.
The Karun-e Bozorg is one of Iran’s river watersheds. Its main river is the Karun, which covers an area of 67,257km2, and five dams are in series across the basin. Karun-4, Karun-3, Karun-1, and Godar-e Landar dams have the primary purpose of hydropower, while the Gotvand dam has the primary purpose of agriculture and a secondary purpose of hydropower. These five dams are operated in parallel with the Dez Dam on the Dez River to supply water for agriculture and hydropower.
This research shows how the evolution of artificial intelligence has resulted in the development of problem-solving techniques and the emergence of optimisation algorithms which have greatly improved the operational performance of reservoirs.
References
Greenhouse gas emissions and footprint analysis of multi-purpose dam reservoirs in temperate climates: Case study from South Korea Kyeongseo Min, Sungjin Kim, Sewoong Chung. Renewable and Sustainable Energy Reviews 225 (2026) 116143. https://doi.org/10.1016/j.rser.2025.116143
A Viability Analysis of Multipurpose Dam System in Rwanda – Renewable Energy for Irrigation, Electricity and Clean Water by Amelia Bergum Alida Nilsson. Master’s thesis 2025. Department of Electrical Engineering Division of Electric Power Engineering Chalmers University of Technology Gothenburg, Sweden 2025. https://odr.chalmers.se/items/f4d03db1-3c00-4094-9970-2cac6f4a8fe7
Optimizing the operation of series and parallel reservoirs using the neutrosophic environment: A case study of the Karun watershed Seyyed Ebrahim Rezai a, Ahmad Sharafati, Seyyed Ahmad Edalatpanah and Saeed Jamali. AQUA — Water Infrastructure, Ecosystems and Society Vol 74 No 1, 92. doi: 10.2166/aqua.2024.359
