The establishment and operation of cascade reservoirs in the mainstream of the upper and middle reaches of the Yangtze River have changed the river’s thermal regimes. This study analyzed the correlation between water temperature and its influencing factors and employed various evaluation indexes—including $∆T$ (the temperature-increasing index, °C/100 km), $I_{EC}$ (the extreme fluctuation index), $I_{BD}$ (the baseline deviation index), and $I_{PO}$ (the phase offset time index). The aim was to uncover the variation characteristics and influencing factors of water temperature and quantify the impact of cascade reservoir construction on annual and seasonal water temperature rhythms. Our findings show that the construction and operation of cascade reservoirs weaken the synchronization of water temperature and air temperature downstream. The construction and operation of cascade reservoirs in the middle and lower reaches of the Jinsha River led to obvious homogenization, baseline deviation, and lagging effects on water temperature downstream, which intensified with the increase in storage capacity. These effects were more pronounced in colder months compared to warmer months. Additionally, the influence of tributaries and water–air heat exchange on these effects is alleviated to different degrees. These results are significant for assessing river ecological health in the context of cascade hydropower development.

We review the research on L. fortunei over the past 22 years, systematically elucidating its impacts on ecological environments and water engineering structures. We explored the effects of external factors on the invasion and spread of L. fortunei, as well as the internal factors that impact the ecological environment and water engineering structures. We also provide new perspectives and directions for L. fortunei control. The major research findings include the following: (1) L. fortunei negatively impacts hydraulic structures, being hard to remove and capable of damaging them, disrupting normal operations. (2) L. fortunei’s ecological impact is multifaceted: it reduces water cloudiness and organic matter by filtering suspended particles and depositing feces, but its decay after death consumes dissolved oxygen, increasing chemical oxygen demand and lowering water quality. (3) L. fortunei control techniques are effective for localized use in small bodies of water and aqueducts, but their control in large open reservoirs is difficult to achieve with one method. Existing control methodologies for L. fortunei were systematically evaluated across multiple dimensions, including engineering applicability and feasibility, technical advantages and limitations, and economic cost-effectiveness. This comprehensive analysis establishes a decision-support framework for optimizing control strategy selection in diverse engineering scenarios and application contexts.