Sediment transport capacity is one of the key parameters in river sediment dynamics. New formulas for fractional and total transport capacity for nonuniform sediment were established and are presented in this paper, based on energy equilibrium and the fact that flow resistance decreases as sediment concentration increases. As this study shows, the transport capacities for a single fraction and total sediment are logarithmic functions of the sediment transport parameter (STP). The proposed formulas based on logarithmic law have many advantages: (1) the critical velocity for suspension of nonuniform sediment is innately embodied with simple form in the logarithmic formulas; (2) the interaction between different size particles was considered in settling velocity for any fraction of nonuniform sediment and the mean settling velocity for nonuniform sediment is equal to the geometric average of settling velocities for a sediment fraction; and (3) the formulas have the same form for fractional and total transport capacity and self-adaptability to uniform sediment. The logarithmic law was verified against laboratory and field data, and was found to perform better than power law. The derived critical velocity for suspension with interaction between nonuniform particles taken into account in the fractional and total critical velocity for suspension was also tested by using laboratory data, and it performs quite well for a wide range of particle diameters despite its simple form. The logarithmic law appropriately depicts the whole suspension process from initiation to transport and thus provides insight into the suspended motion of nonuniform sediment.

The sedimentation problem is one of the critical issues affecting the long-term use of rivers, and the study of sediment variation in rivers is closely related to water resource, river ecosystem and estuarine delta siltation. Traditional research on sediment variation in rivers is mostly based on field measurements and experimental simulations, which requires a large amount of human and material resources, many influencing factors and other restrictions. With the development of computer technology, intelligent approaches have been applied to hydrological models to establish small information in river areas. In this paper, considering the influence of multiple factors on sediment transport, the validity of predicting sediment transport combined with wavelet transforms and neural network was analyzed. The rainfall and runoff cycles are extracted and decomposed into time series sub-signals by wavelet transforms; then, the data post-processing is used as the neural network training set to predict the sediment model. The results show that wavelet coupled neural network model effectively improves the accuracy of the predicted sediment model, which can provide a reference basis for river sediment prediction.

With the operation of six cascade reservoirs, the flow regime and sediment discharge of the Lancang River have changed greatly. The changes of runoff and suspended load have attracted extensive attention. The hydrological data of Gajiu and Yunjinghong stations in Lancang River from 1964 to 2019 were analyzed by using wavelet analysis, double mass curve and abrupt change analysis. The temporal trends in runoff and suspended load were evaluated. Results revealed that the reduction of suspended load was much more profound than the change of runoff. There was a slight downward trend in annual runoff due to climate change. After the completion of Xiaowan and Nuozhadu reservoirs, the proportion of runoff in flood season decreased by 22.64 and 30.75%, respectively. Wavelet analysis was used to reveal the characteristics of runoff evolution. With the operation of reservoirs, suspended load showed abrupt changes in 1993 and 2008. The amount of suspended load during 2009–2019 decreased by 95.47–98.78% compared with that before the reservoir construction. This paper presents the latest quantitative study on the temporal variation of runoff and suspended load since the completion of Xiaowan and Nuozhadu reservoirs, which is of great importance for guiding the operation of reservoirs and maximizing the value of the whole Lancang-Mekong River basin.

Flow resistance, velocity distribution, and turbulence intensity are significantly influenced by aquatic vegetations (AV) in riparian zones. Understanding the hydraulics of flow with planted floodplains is of great significance for determining the velocity distribution profile and supporting the fluvial processes management. However, the traditional flume experiment method is inefficient. Therefore, the multigroup simultaneous flume test method was carried out to describe the flow patterns affected by emerged rigid (reed and wooden stick) and submerged flexible vegetations (grass and chlorella). The Acoustic Doppler Velocimeter (ADV) was utilized to measure the velocity at one point for different experimental conditions. The results showed that hydraulic features were influenced by different types of vegetation. Furthermore, the relative depth (z/h) was a determining factor of those variations. In addition, the time-averaged velocity distributions of planted floodplains are not logarithmic. Instead, they represented “s-shape” profiles. In detail, for the vegetated floodplains, reed and wood followed an s-shape profile, but for grass and chlorella, they followed reverse s-shape profile. For all cases, turbulence is not isotropic and the change law of turbulence intensity is different in different sections. The flow resistance, turbulence intensities, and Reynold stresses influenced by different types of vegetation were also analyzed.

The research on water and sediment variations is of great importance for regional resource and watershed management. Studying the relationship between precipitation, runoff and sediment load, traditional methods are based on observational data fitted or artificial intelligence predictions, whose accuracy is directly dependent on the quality and quantity of the data. This paper developed a new approach for researching the relationship between precipitation, runoff and sediment load. Based on the sliding accumulative anomaly method, the M-K mutation analysis and the wavelet functions, variation of precipitation and runoff annually were discussed. The results indicated the annual variation trend of the precipitation and runoff have been consistent since 1969, both with a 28-year main cycle, and runoff variations were less subject to human influence in the Luozha River. Therefore, the formula of the relationship between annual runoff and sediment load can be obtained by integrating discrepancy in the magnitude of its variation in the natural state, which was verified by the observational data and was applicable to acquisition of annual sediment load. The current work broadens the current knowledge of recent changes in the Lancang River Basin and improves the recognition of the water-sediment interrelation in the river.

In order to reasonably use solar energy to solve problems such as land desertification and soil salinization in Southern Xinjiang, this paper proposes a system combining photothermal and flash evaporation technologies, which use local saline water for desalination treatment to achieve secondary utilization of water resources. Firstly, we introduce the whole system of the photovoltaic desalination plant. As an important heat-collecting element of the system, the solar tube is the key to whether this plant can work efficiently. Then, we carry out the detection and theoretical derivation of data along the tube. We establish a two-phase flow model of saline water in the tube, considering convective heat transfer, and define the formula of the heat collecting efficiency factor. Finally, based on iterative calculation, the temperature trend of the tube and the change law of the two-phase flow are obtained, and the ecological and economic benefits and energy efficiency of the system are analyzed.