Methane (CH4) has a large contribution to the global greenhouse effect. The CH4 emission from the Three Gorges Reservoir has attracted considerable attention since its impoundment in 2003. However, the unique operation mode of the Three Gorges Reservoir affected the CH4 emission and transport in its tributaries. However, the underlying mechanism of CH4 emissions remains unclear. This study reviewed the research progress of CH4 emission from the tributaries of the Three Gorges Reservoir. The CH4 fluxes of typical tributaries were generally higher than those of the main streams. The CH4 emission flux of some tail tributaries of the Three Gorges Reservoir was higher than that of the head and tributaries. The CH4 fluxes in most typical tributaries have peak values in summer, and relatively low values during high water operation in winter. The factors influencing CH4 emission from these tributaries mainly included algae, climatic factors, hydrodynamic conditions and human activities. The future research hotspots were summarized. 1) Algae; The impoundment of the Three Gorges Reservoir has led to intensified algal blooms in some of its tributaries. The dominant species of phytoplankton gradually changed from river-type algae to lake-type algae in the early stage of water storage. This succession of phytoplankton would increase CH4 production. In addition, the algal bloom in tributaries of the Three Gorges Reservoir, would undergo seasonal succession. Phytoplankton dominated by green algae and cyanobacteria has high contribution to CH4 emission. 2) Climatic factors; The generation and consumption rate of tributary CH4 were positively correlated with temperature. In general, higher temperature promote the growth of algae. However, the out-of-season scheduling mode of the Three Gorges Reservoir also enhances phytoplankton production in winter. The tributary temperature stratification would further aggravate algal bloom, providing substrate for CH4 production. Rainfall affected CH4 discharge of these tributaries by increasing the content of organic matter, the abundance of methanogenic bacteria, and disturbing the surface water. The degree of impact was related to the magnitude of rainfall runoff. 3) Hydraulic conditions; During the low water level period of the Three Gorges Reservoir, CH4 consumption in the water body was lower enhancing CH4 transmission. Moreover, the water level change caused by the operation of the reservoir also affects environmental factors such as temperature stratification, algae growth and organic matter distribution, which has an indirect impact on the CH4 flux of tributaries. 4) Human activities; Land use changes caused by human activities would increase nutrient concentrations in tributary water bodies and enhance nutrient-related metabolism of bacterial communities, resulting in an increase of CH4 emission. The damming and reservoir operation in the tributary area changed the hydrodynamic conditions of the tributary, blocked the transport of organic matter, and thus increased the total organic carbon content in the sediment, providing more substrate for CH4 production. Finally, the future research hotspots were summarized to provide scientific basic for the management of CH4 emissions in the Three Gorges Reservoir. © 2024 Science Press. All rights reserved.
