The contribution of ecosystem water supply services in the Qinghai section of the Yellow River Basin to hydropower-based carbon reduction in the Entire Basin

Quantifying the transregional contribution of water supply services to hydropower production and carbon mitigation is of great practical significance. This study integrated runoff observations, statistical data, and model simulations to develop an assessment framework for the contribution of the Qinghai section's water supply services to hydropower carbon reduction. Then, we analyzed the contribution of water supply to downstream hydropower carbon reduction from 2000 to 2022. The results indicated that: (1) The long-term average water supply of the Qinghai section was approximately 98.9 mm. From 2000 to 2022, the water supply showed a significant increasing trend at a rate of 2.31 mm/a. (2) The average annual amount of hydropower carbon reduction in the Qinghai Basin was 32.88 million tons of CO2e, with Qinghai's contribution reaching 25.77 million tons of CO2e/a, accounting for approximately 78.4%. (3) In the main stem of the Yellow River outside Qinghai province, the long-term average hydropower carbon reduction was 24.43 million tons of CO2e/a, of which Qinghai's contribution amounts to 9.09 million tons CO2e/a, accounting for about 37.2%. From 2000 to 2022, this contribution exhibited a slight upward trend, increasing at a rate of 0.23 million tons CO2e/a. (4) The total carbon reduction from all the hydropower stations along the Yellow River mainstream was 57.31 million tons of CO2e/a, with Qinghai contributing 34.85 million tons of CO2e/a, representing 60.8%. From 2000 to 2022, Qinghai's contribution to hydropower carbon mitigation in the Yellow River Basin increased at a rate of 1.28 million tons CO2e/a. This study provided a theoretical reference for a better understanding of the comprehensive benefits of water supply service flows. It further suggested incorporating the indicator of "hydropower's contribution to carbon emission reduction" into the accounting indicator system for watershed ecological compensation, aiming to facilitate a win-win scenario between ecological protection and economic development.