Evaluating the impact of power station regulation on the suitability of drifting spawning fish habitat based on the fuzzy evaluation method.

Ecological regulation is an important means of reservoir adaptive management, but its effective evaluation faces two major difficulties: the response mechanism of fish spawning behavior is not completely clear, and how to establish a feedback regulation relationship of hydrological processes to improve the river environment is unknown. Based on a long-term series of early fish resources, hydrology, water temperature, and meteorology data, this research clarifies the fish spawning habitat requirements in the power station regulation environment, determines a habitat suitability evaluation index system and evaluation criteria, reveals the temporal and spatial variation characteristics of fish habitat suitability under power station regulation based on the fuzzy logic method, provides feedback to the existing regulation scheme, and proposes suggestions for sustainable adaptive management of the reservoir. The temporal and spatial variation characteristics of the spawning river sections habitat suitability are the comprehensive differences among multiple objectives and factors. The habitat suitability of each river section decreases after impoundment, especially in May, which is related to the delayed of water temperature changes under reservoir regulation. The reduced suitability of the Yibin(YB) river section is most affected by the impoundment regulation of the Xiluodu Reservoir (XLDR) and Xiangjiaba Reservoir (XJBR), while the Luzhou(LZ) river section is affected by the inflow of the Minjiang River (MJ) tributary, which reduces the suitability difference before and after impoundment. The Jiangjin(JJ) river section is less affected by the regulation of the XJBR and is greatly affected by tributaries and rainfall. How to adjust the regulation strategies under the new boundaries and new situations in the future, which are affected by the cumulative impact of the sustainable development of upstream cascades, is the focus of reservoir adaptive management. This research can provide technical support for the management of cascade reservoirs under future scenarios.

Identifying three-dimensional swimming corridors for fish to match their swimming characteristics under different hydropower plant operations: Optimization of entrance location for fish-passing facilities.

Fish that require migration are often diverse in the dam-built river, and some of them are benthic. For fish to pass efficiently across the dams, it is necessary to identify the swimming corridors and possible cluster areas of the target fish. However, previous studies have only predicted the two-dimensional swimming corridors of a single species. In this study, the relationships between the swimming behaviours of different species of fish and the three-dimensional (3D) hydrodynamic field were determined, and a model of the 3D swimming corridors corresponding to the fish swimming characteristics was constructed. The model was verified by a fish acoustic telemetry experiment. By simulating the river 3D hydrodynamic field in different scenarios, the possible swimming corridors and clustering areas of the target fish were further evaluated. We showed that the swimming corridors of the target fish were different among different scenarios, and the swimming corridors were mainly concentrated on both sides of the mainstream. With increased flow due to power station operation, the proportion of potential swimming corridors of target fish throughout the basin gradually decreased, and the proportion of velocity barrier zones of target fish gradually increased. By analyzing the possible swimming corridors of the target fish, the slow-flowing areas near the suddenly narrowed swimming corridors were considered to be the areas of target fish clustering. The cluster areas of the target fish weres also the optimal choice of the fish passing facility entrances, so as to ensure the best fish-crossing effect. The reliable and quantitative 3D fish swimming corridors model proposed in this study can provide a scientific basis for the layout of fish-crossing facilities and facilitate the scientific operation and management of the reservoir in the fish spawning season.

Risk assessment and source apportionment of trace elements in multiple compartments in the lower reach of the Jinsha River, China.

Studies on trace element (TE) pollution in abiotic matrices have typically focused on water, sediment, and soil, either separately or in pairs. The importance of multi-media connectivity has been ignored. This study analyzed the concentrations of 6 TEs in three connected environmental compartments of a 28-km section of the lower reach of the Jinsha River. The ecological risk posed by TEs was higher in soil than in sediment. The contribution of exposure pathways to human health risk were ranked as ingestion > dermal contact > inhalation. An improved regional environmental risk index (RERI) method was then developed to evaluate the comprehensive risk on both ecology and human health caused by TEs. The average RERI value was generally higher in the wet season (0.42) than in the dry (0.41) and dry-to-wet transition seasons (0.08) because of the combined effects of the high TE concentrations in riparian soil and the long exposure time. Source apportionment indicated that industrial activities, weathering of parent rock, and agricultural activities were possible sources of TEs in this region. The methods and results of this study could inform local environmental management and provide references for similar cases wherein multiple compartments of river systems should be considered.

Energy dissipation efficiency as a new variable in the empirical correlation of total dissolved gas.

Total dissolved gas (TDG) supersaturation, which occurs during dam spilling, may result in fish bubble disease and mortality. Many studies have been conducted to identify the factors pertaining to TDG generation, such as the spilling discharge and tailwater depth. Additionally, the energy dissipation efficiency should be considered due to its effect on the air entrainment, which influences the TDG generation process. According to the TDG field observations of 49 cases at Dagangshan and Xiluodu hydropower stations, the TDG was positively related to the energy dissipation efficiency, tailwater depth and discharge per unit width. A correlation between the generated TDG level and these factors was established. The empirical equations proposed by the USACE were calibrated, and the TDG level estimation performance was compared with the established correlation for 25 spillage cases at seven other dams. Among the considered cases, the standard error of the TDG estimation considering the energy dissipation efficiency was 5.7%, and those for the correlations obtained using the USACE equations were 13.0% and 10.0%. The findings indicated that the energy dissipation efficiency considerably influenced the TDG level, and its consideration helped enhance the precision of the TDG estimation. Finally, the generality of this approach and future work were discussed.