Assessing Climate-Driven Greenhouse Gas Emissions from Feitsui Reservoir Using G-RES Under Multiple SSP Scenarios

Reservoirs are increasingly recognized as significant sources of greenhouse gas (GHG) emissions, yet their future emissions under climate change remain poorly quantified. This study evaluates the impact of climate change on net GHG emissions from Feitsui Reservoir, a major water supply reservoir in northern Taiwan, using an integrated modeling approach.

We utilized the multisite Weather Generator (multiWG) to generate future climate projections for three Shared Socioeconomic Pathways (SSP126, SSP245, SSP585) across four 20-year periods (2021-2040, 2041-2060, 2061-2080, 2081-2100), with 1995-2014 as the baseline. A Random Forest model (NSE = 0.8637) was trained to predict reservoir inflow based on temperature and precipitation data. These inflows were input into the G-RES model to calculate net GHG emissions in CO₂-equivalent units, including contributions from both CO₂ and CH₄.

Results reveal that reservoir GHG emissions will increase under all climate scenarios, with magnitude strongly dependent on emission pathways. Under the low-emission scenario (SSP126), emissions increase by 5.2-8.8% across all periods. The intermediate scenario (SSP245) shows moderate increases of 5.4-18.4%. The high-emission scenario (SSP585) demonstrates dramatic escalation, particularly in the late century (2081-2100), where emissions reach 1259.6 gCO₂e/m²/yr—a 45.8% increase. These findings underscore the critical need to consider climate impacts in reservoir management and carbon accounting frameworks.