Review on the externalities of hydropower: A comparison between large and small hydropower projects in Tibet based on the CO2 equivalent

In the case study of 5 LHPs (>50 MW) and 10 SHPs in Tibet, China, SHPs have reduced externalities compared to LHPs, with SHPs and LHPs representing a burden of 5.1 and 29.2 gCO2-ekW h−1 on average, respectively. This extra carbon emission burden indicates that the present low-carbon potential of hydropower has been overestimated. Meanwhile, this reduced externality makes SHPs perform better in terms of environmentally friendly development and low-carbon energy than LHPs for Tibet. The externality caused by reservoir impoundment and occupation is the primary component of the total externality of a LHP; therefore, increasing the power density is an efficient way to decrease its externality.