A modeling approach to assess the greenhouse gas risk in Koteshwar hydropower reservoir, India

ABSTRACT

Climate changes are likely to be significantly affected by reservoirs/lakes due to emission of greenhouse gas (GHG), change in the magnitude and seasonality of river runoffs and severe extreme events. In this study, a coupled GHG Risk Assessment Tool (GRAT) and Soil Water Assessment Tool (SWAT) are used to predict the GHG risk of Koteshwar reservoirs located in Uttarakhand, India. Before running the GRAT model, SWAT model was used to simulate the runoffs (one of the major input of GRAT). The model was calibrated (2004–09) and validated (2010–13) at Uttarkashi station using monthly discharge data. The model performance was checked by R², NSE, RSR, and p-value as 0.785, 0.60, 0.63, and 0.04, respectively, during calibration and 0.790, 0.66, 0.57, and 0.06 during validation and shows satisfactory model performance on monthly time step. Further, GRAT model is also applied and the results show that Koteshwar reservoir is found to be under high risk of CO₂ (CO₂ > 645 mg m⁻² d⁻¹) and medium risk of CH₄ (CH₄ < 45 mg m⁻² d⁻¹) till 2023. Subsequently, the GHG risk is minimized after passage of time over 100 years. These models may be used by the policy-makers to know the potential of GHG and its vulnerability to the reservoirs after the impoundment.

KEYWORDS:

• SWAT
• GRAT
• risk
• greenhouse gas
• runoffs

Acknowledgments

The authors are very grateful to the reviewers for their valuable comments/suggestions.

Funding

One of the authors (AK) acknowledges the financial support from the Ministry of Human Resource Development, Government of India, in the form of a fellowship to carry out this research work.