关键词: 梯级水电, 局地气候, 生态效应, 间接影响, 流域累积, 金沙江干热河谷

Abstract:

The development of cascade hydropower refers to the construction of a series of water conservancy projects in a stepped manner on the same river or river basin with the aim of systematically utilizing water resources. Through rational planning and scheduling, it maximizes the comprehensive benefits of water resources and realizes the full utilization and orderly allocation of water resources. Cascaded hydropower development can not only effectively improve the development and utilization efficiency of hydropower resources, but also provide technical support for regional energy structure optimization and ecological environment restoration. This study revealed the latest progress in the impact of hydropower development on the local climate, ecological effects, and cumulative effects of cascaded development in recent years. It focuses on discussing issues such as the local climate impacts of reservoirs and their influencing and constraining factors, the direct and indirect impacts of hydropower development on terrestrial ecology, and the cumulative ecological effects of cascaded hydropower development. In particular, it explores the local climate and ecological effects of hydropower development in the Jinsha River dry-hot valley, a typical ecologically fragile area. The results showed that, for large-scale water conservancy projects, the construction and operation of reservoirs have a significant impact on the local climate, mainly reflected in changes in factors such as humidity, temperature, and precipitation, with obvious seasonal differences. Reservoirs affect the temperature and precipitation patterns of the surrounding areas by regulating water evaporation and heat capacity, and simultaneously changing climatic factors such as wind speed and direction. Conversely, changes in the local climate can also cause changes in parameters, such as the water level, water temperature, and water quality of the reservoir, thus affecting the water supply, power generation efficiency, and ecological environment of the reservoir. A complex interaction mechanism is formed between the reservoir and climate, which requires in-depth research to develop scientific management strategies. The response of ecosystems to hydropower development involves both aquatic and terrestrial ecosystems. Research has shown that its impacts are complex and diverse. Hydropower development changes hydrological conditions in terms of aquatic ecology, such as water flow velocity, runoff, water level, and water quality; destroys biological habitats; alters the living environment of aquatic organisms; and may block migration routes, leading to a decline in species quantity and genetic diversity. In terms of terrestrial ecology, hydropower development leads to land expropriation and changes in landscape patterns, increases soil erosion, causes vegetation degradation, and causes the loss of biological habitats, thus affecting the distribution of species and food chain. In addition to the direct impacts on ecology during the construction process of hydropower development, it also affects river hydrological characteristics, soil environment, and local climate, thus having more complex and far-reaching indirect impacts on terrestrial ecology. Compared with a single hydropower station, the cumulative effects of cascaded hydropower development on the local climate and ecology of the entire river basin are more significant, exhibiting characteristics such as system superposition, blocking differentiation, potential hysteresis, and factor selectivity. System superposition means that a series of dams built during cascaded hydropower development jointly forms a complex system with social and natural attributes. Although dam construction affects the natural connectivity of the river, various parts of the system maintain a relationship of mutual connection, influence, and constraint. Local changes had a cumulative effect on the entire system. The comprehensive impact of the entire system on the ecological environment is not simply the sum of the effects of a single dam, but the mutual influence and compound superposition of its components. Blocking differentiation is due to the blocking effect of cascaded dams on the river. The comprehensive impacts of hydropower development on river ecosystems in the upstream and downstream blocked reaches gradually accumulate over time and space, resulting in the differential manifestations of the same ecological elements. Potential hysteresis means that the impacts of dam construction and operation on the river ecosystem are insignificant in the initial stage. However, over time, these impacts will gradually accumulate and become significantly apparent at a certain point in the future, with long-term and complex impacts on the ecological environment. Factor selectivity means that the cumulative effects of cascaded hydropower development do not act on all ecological elements, and must be comprehensively considered according to the spatiotemporal characteristics of the study area. The Jinsha River dry-hot valley is an ecologically fragile area and an important hydropower development region in China. Due to the special geographical and climatic conditions of this area, the impacts of hydropower development on the local climate and ecological environment are particularly significant. Research has found that the hydropower development of the Jinsha River shows a comprehensive change in climate, which is the combined effect of global climate change and the local climate impact of the reservoir. In terms of ecological effects, most research has focused on the direct impacts of hydropower development on dry-hot valley areas during the development process, while there is less research on the indirect impacts of hydropower development on terrestrial ecology by changing local hydrothermal conditions and affecting the local climate. Changes in local climate can promote the restoration and renewal of vegetation in reservoir areas and affect the evolutionary direction of plant populations. In summary, while cascade hydropower development enhances energy utilization efficiency and contributes to regional economic development, it also produces significant and complex effects on local climate and ecosystems. These effects exhibited complex spatial and temporal interactions. Although numerous studies have been conducted, gaps remain in the understanding of the comprehensiveness of climatic factors, systematic ecological response mechanisms, and spatial-temporal differentiation of local climate effects. Future research should integrate interdisciplinary techniques to identify the local climate effects of hydropower development more precisely, particularly by excluding the influence of global climate change. In addition, a more in-depth study of the ecological responses at the watershed scale, especially the cumulative effects of multiple hydropower stations, is essential. Research should also account for regional differences and propose targeted research plans for multiscale multidimensional assessments to reveal the spatial differentiation patterns of both direct and indirect ecological responses. These efforts will help address the ecological and environmental challenges posed by cascade hydropower development and contribute to achieving the “ecology-first” principle outlined in China’s “Carbon Peak and Carbon Neutrality” goals. Based on these findings, this study offers the following recommendations for cascade hydropower development projects: 1) Establish a comprehensive watershed management system to coordinate the operations, environmental protection, and ecological restoration efforts of each hydropower station, fostering cross-regional collaboration and resource sharing to enhance the overall efficiency of the cascade hydropower stations. 2) Develop a multidimensional monitoring system to regularly collect and analyze climate and ecological data, enabling dynamic tracking of climate change and ecological responses after hydropower station operations, and providing timely intervention when potential ecological degradation or abnormal climate patterns are detected. 3) During the project design and implementation phases, a robust ecological compensation and restoration mechanism, including environmental assessments and planning before reservoir construction as well as continuous ecological restoration and protection measures, following the completion of hydropower projects.

Key words: cascade hydropower, local climate, ecological effect, indirect effects, watershed accumulation, Jinsha River dry-hot valley