Sediment-laden River Research Articles

Wear fault diagnosis in hydro-turbine via the incorporation of the IWSO algorithm optimized CNN-LSTM neural network

When a hydropower unit operates in a sediment-laden river, the sediment accelerates hydro-turbine wear, leading to efficiency loss or even shutdown. Therefore, wear fault diagnosis is crucial for its safe and stable operation. A hydro-turbine wear fault diagnosis method based on improved WT (wavelet threshold algorithm) preprocessing combined with IWSO (improved white shark optimizer) optimized CNN-LSTM (convolutional neural network-long-short term memory) is proposed. The improved WT algorithm is utilized to denoise the preprocessing of the original signals. Chaotic mapping, bird flock search, and cosine elite variation strategies are introduced to enhance the WSO algorithm's robust performance, and the CNN-LSTM model's hyperparameters are optimized using the IWSO algorithm to improve the diagnostic performance. The experimental results show that the accuracy of the proposed method reaches 96.2%, which is 8.9% higher than that of the IWSO-CNN-LSTM model without denoising. The study also found that the diagnostic accuracy of hydro-turbine wear faults increased with increasing sediment concentration in the water. This study can supplement the existing hydro-turbine condition monitoring and fault diagnosis system. Meanwhile, diagnosing wear faults in hydro-turbines can improve power generation efficiency and quality and minimize resource consumption.

Research on Sediment Erosion and Anti-Wear Coating Materials for Water-Intake Components of Hydraulic Turbines in Sandy Rivers

The operational efficiency, stability, and lifespan of hydroelectric power plants operating on sediment-laden rivers are affected by sediment erosion. A numerical simulation of the sand–water flow in the water-intake components of a turbine at a specific power station was conducted using the Euler–Lagrange method. Additionally, sediment erosion tests were carried out on the water-intake components coated with epoxy mortar material. The results indicate that sediment erosion on the stay vane surface mainly occurs on the front face, with the most severe erosion at the head, while sediment erosion on the stay ring surface primarily occurs near the stay vane head. The extent of erosion is mainly influenced by the distribution characteristics of sediment particles. The wear of epoxy mortar coating material is minimally affected by the spraying thickness. Adding 30% hardener to the epoxy mortar material can significantly improve the erosion resistance of the stay vane surface by about 30%. The erosion rate on the frontside of the stay vane is approximately 2.6 times that of the backside. Based on the sediment erosion tests and numerical simulation results of the sand–water flow, an estimation formula for the sediment erosion rate of the epoxy mortar erosion-resistant coating was established. This formula can be used to predict the anti-sediment erosion performance of epoxy mortar materials applied to the water-intake components of this turbine and similar river turbines.

Morpho-hydrodynamic processes impacted by the 2022-extreme La Niña event and high river discharge conditions in the southern coastal area of West Java, Indonesia

ABSTRACT The significance of sediment-laden river discharges is strongly related to climate change and rainfall intensity, resulting in severe erosion of the catchment areas and riverbanks. The combination of tides and waves considerably influence the sediment transport and distribution patterns of an estuary, inducing the sedimentary processes of the coastal area. This study aims to analyze the impacts of the La Niña event in 2022 and high river discharges in the Bojong Salawe Beach, Pangandaran. This area has a large estuary with several tributaries, with a high potential for erosion and sedimentation. Furthermore, its location directly faces the Indian Ocean, posing the risk of wind-induced high waves. The methods used in this research are descriptive analysis (using dataset ERA-5 taken from the Copernicus Climate Change Service) and numerical models (using Mike21) with an identification of erosion and accretion processes. The results show that the boreal autumn 2022 significantly impacted the study area, compared to the boreal winter 2022. Higher precipitation levels during boreal autumn substantially increased the river discharges, transferring the total load of sediment of about 1.48 × 10−3 m3/s/m. Moreover, shoreline change analysis using digital shoreline analysis system confirmed that Bojong Salawe Beach was indicated to experience high erosion, particularly around the mouth of the estuary.

Study on erosion characteristics of turbine in sediment-laden river

Abstract Sediment erosion of hydro turbines is prevalent and serious in the mountain river region. The effect of operating head and particle diameter on sediment erosion was investigated in this paper. A Eulerian-Lagrangian approach was applied to numerically simulate the solid-liquid flow in a Francis turbine under the minimum, design and maximum heads. Five typical diameters (0.1, 0.3, 0.5, 0.7, 0.9 mm) were firstly determined based on field measurements at a hydropower station. After tracking the trajectories of sediment particles, McLaury model was selected to predict the erosion rate. The results show that sediment erosion regions of runner blades are similar under different operating heads, while the sediment erosion rates amplify significantly with the increase of operating heads. The erosion rate of blade suction side is significantly higher than that of pressure side because of the effect of inter-blade vortices between runner blades. Sediment diameters also play an important role in accelerating erosion rate, which indicate that setting up sedimentation tanks to settle large-size sediment particles is a powerful method to alleviate sediment erosion. This study can provide a reference for erosion estimation and operational maintenance of hydro turbines in mountain river region.

How the Water-Sediment Regulation Scheme in the Yellow River affected the estuary ecosystem in the last 10 years?

The Yellow River, renowned as the most sediment-laden river globally, grapples with sediment deposition issues compromising reservoir functionality and elevating downstream riverbeds, posing threats to human life and property safety. In response, the Water-Sediment Regulation Scheme (WSRS) has been innovatively implemented to address these challenges. While effectively mitigating sediment deposition, WSRS has concurrently disrupted the equilibrium of the estuarine ecosystem. This paper addresses the understudied but crucial topic of the interannual impact of WSRS on the estuarine ecosystem. Drawing upon physical, chemical, and biological data gathered through field surveys conducted before, during, and after WSRS from 2011 to 2022, the analysis delves into the interannual changes in the estuarine environment, fish eggs and larvae abundance, and species diversity under the influence of WSRS. The findings reveal an interannual decreasing trend in terrestrial material input due to WSRS, juxtaposed with an interannual increasing trend in fish eggs and larvae around the estuary, as well as the species diversity index. Notably, these trends became more pronounced post-2014. Compared to pre-2014, nutrient concentrations experienced a ~20 % decrease, chlorophyll-a concentration increased by 44 %, fish eggs proliferated approximately 1 time, and the species diversity index transitioned from a declining trend to an ascending trajectory. After 12 years of continuous WSRS implementation, the impact on the estuarine ecosystem has demonstrably diminished. This research aims to furnish reference experience and scientific basis for water and sediment regulation in major rivers around the world in terms of estuarine ecology.

Effect of multiple factors on sediment erosion characteristics of hydro turbine materials

Hydraulic turbines on sediment-laden rivers suffer from cavitation-silt erosion. This study conducted cavitation-silt erosion tests on three materials (06Cr16Ni5Mo, Q355B, 06Cr20Ni11) with different sediment concentrations and impact velocities using a rotating disk facility, and used a scanning electron microscope (SEM) to observe the cavitation-silt erosion characteristics of the materials. The results show that the cumulative weight loss of all materials continuously increases with the sediment concentration and impact velocity rises. The weight loss of 06Cr16Ni5Mo is the lowest, and 06Cr20Ni11 is the highest. As the impact velocity rises, the cumulative weight loss increases exponentially. As the sediment concentration rises, there are obvious scour marks and fatigue spalling on the material surface. As the impact velocity rises, the size and depth of micro-cutting marks and cavitation pits increases. Due to the lower surface hardness of 06Cr20Ni11, the deep platelet pits appear on the material surface.

Analyzing Water and Sediment Flow Patterns in Circular Forebays of Sediment-Laden Rivers

In the circular forebay of sediment-laden rivers, adverse flow patterns such as vortices emerge, leading to substantial sediment accumulation along the sidewalls of the diversion channel and in the forebay. This sediment accumulation significantly impacts the operational efficiency of water pumps. To address these challenges, a combination of numerical simulations and engineering experiments was employed to reveal the factors contributing to the development of these patterns. Based on these findings, seven distinct flow rates and operating conditions were introduced to obtain the optimal inlet flow rate and increase the sustainability of engineering use. The findings revealed that the different inlet flow rates exert varying influences on the flow patterns in the circular forebay, leading to changes in sediment levels in both the forebay and diversion channels. Following comprehensive comparison, Scheme 6 was identified as the optimal flow rate scheme. In this scheme, the flow uniformity, deviation angle, ratio of the vortex reduction area parameter, and rate of vortex area reduction in sections z1−3 were markedly enhanced. The effectiveness of this scheme was validated through rigorous numerical simulations and engineering experiments, thereby offering indispensable theoretical insights into the operation of pumping stations in circular forebays.

Detecting the magical yellow-blue demarcation off the Yellow River Estuary from the space

River deltas rank among the most ecologically and socio-economically valuable environments on the planet. The Yellow River Delta in China is not only home to young wetland ecosystem, but also to world-renowned tourism resources. One of these was the unique yellow-blue demarcation line (YBDL), formed in the Yellow River Estuary (YRE) as a result of the meeting of terrestrial sediment-laden river water and clear sea water, which had developed into a famous attraction and generated significant tourism revenues. Moreover, its distribution was of vital ecological and geomorphological importance due to association with the dynamics of estuarine turbidity plume. However, little is yet known about the dynamics and influencing factors of YBDL. In this study, we proposed an integrated method for extracting YBDL from satellite imagery and investigated the spatiotemporal distributions of YBDL during the flood season (June-October) from 2016 to 2022 using multi-source satellite imageries. The average relative error of our algorithm reached 10.53%. The results indicated that the YBDL started to frequently occur after 2018, mainly distributed within 10 km off the YRE, with two types of short straight and long curved shapes. July was the period with the highest frequency and most widespread distribution of YBDL. The riverine water and sediment discharge controlled 45.9% of the variations in YBDL length, and the extreme flooding, as well as the implementation of Water-Sediment Regulation Scheme, significantly increased the distribution extent of the YBDL. The morphology of river distributary mouths dominated the changes in the YBDL distribution centres, and the north distributary mouth experienced dramatic evolution in the last three years, with an increased YBDL distribution. Tidal currents could promote the development of YBDL at the front of the river mouth plumes while inhibiting the YBDL on the other side. This study is the first systematic investigation of the spatiotemporal evolutions and driving mechanisms of YBDL in the YRE, which could provide a reference for tourism planning and YRE National Park construction.

Optimizing the Flood Limit Water Level of Reservoirs in Sediment-Laden Rivers under Changing Water and Sediment Conditions: A Case Study of the Xiaolangdi Reservoir

Optimizing the flood limit water level (FLWL) of reservoirs in sediment-laden rivers under changing water and sediment conditions is an important research topic that could improve comprehensive utilization benefits. Because reservoir operation has multiple objectives in sediment-laden rivers, this study established a water–sediment mathematical model, a comprehensive benefit evaluation model, and an evaluation index system. Taking the Xiaolangdi Reservoir of the Yellow River as an example, the operation mode of the FLWL under changing water and sediment conditions was studied. Under the scenarios of incoming sediment amounts of 300–800 million tons, when using the operation mode of gradually raising the FLWL, the sediment retention period was 4–13 years longer; the lower average annual siltation of the downstream channel and minimum bank-full discharge of the downstream channel after 50 years was larger by 150–260 m3/s than the operation mode of raising the FLWL at one time. However, with enhanced benefits of sediment blocking and siltation reduction, other benefits such as water resources supply, hydropower generation, and ecological improvement are reduced. The average annual number of days that do not meet the downstream water resources supply requirements, irrigation, and ecological improvement was increased by 0.64–2.16 days, and 91–197 million kW·h reduced average annual hydropower generation. The critical amount of incoming sediment was 350 million for conversion between the two FLWL operation modes, and it will increase to 450 million tons if the incoming runoff of the Yellow River increases by 20%. After constructing the Guxian Reservoir in the middle of the Yellow River, the critical amount of incoming sediment will increase to 600 million tons. This study is of great significance for improving the utilization efficiency of water resources and promoting the socio-economic development of river basins.

Spatiotemporal Evolutions of the Suspended Particulate Matter in the Yellow River Estuary, Bohai Sea and Characterized by Gaofen Imagery

Suspended particulate matter is a crucial component in estuaries and coastal oceans, and a key parameter for evaluating their water quality. The Bohai Sea, a huge marginal sea covering an expanse of 77,000 km² and constantly fed by numerous sediment-laden rivers, has maintained a high level of total suspended particulate matter (TSM). Despite the widespread development and application of TSM retrieval algorithms using commonly available satellite data like Landsat, Sentinel, and MODIS, developing TSM retrieval algorithms for China’s Gaofen (GF) series (GF-6 and GF-1) in the Bohai Sea is still a great challenge, mainly due to the limited applicability of empirical algorithms. In this study, 259 in situ measured-TSM samples were collected for algorithm development. The remote sensing reflectance (Rrs) curve demonstrates prominent peaks between 550 and 580 nm. Through conversion to remote sensing reflectance, it was found that single-band data had a weak correlation with TSM, reaching a maximum correlation of 0.44. However, by combining bands of band ratio calculations, the correlation was enhanced. Particularly, the blue and green band equivalent Rrs ratio had a correlation coefficient of 0.81 with TSM, and the proposed TSM inversion exponential algorithm developed based on this factor obtained an R-squared (R²) value of 0.76 and a mean relative error (MRE) of 32.24%. Analysis results indicated that: (1) there are spatial variations in the TSM within the Bohai Sea, Laizhou Bay, and the Yellow River estuary, with higher levels near the coast and lower levels in open waters. The Yellow River estuary experiences seasonal fluctuations higher TSM during spring and winter, and lower variations during summer and autumn, and (2) the dynamics of TSM are affected by Yellow River runoff, with increased runoff leads to higher TSM levels and expanded turbid zones. This study proposes a new algorithm to quantify TSM evolutions and distributions in the Bohai Sea and adjacent regions using China’s Gaofen imageries.

Niche processes shape zooplankton community structure in a sediment-laden river basin

Niche processes shape zooplankton community structure in a sediment-laden river basin

Reservoir ecological operation on sediment-laden river considering wetland protection

Reservoir ecological operation has become an important means of ecological protection and restoration. The operation of reservoirs on sediment-laden rivers with water supply, sediment transport, flood control, wetland protection, and power generation as the primary objectives is a challenge in water resources management. Currently, most studies on reservoir ecological operation models involve a single ecological objective, and the inadequacy of the corresponding ecological constraint conditions makes it difficult to optimize reservoir ecological operation. To address these challenges, this study considers comprehensive water shortage, ecological water shortage, effective sediment transport in the river, and reservoir power generation as objective functions to establish an ecological operation model of sediment-laden river reservoirs for wetland protection. In this model, the ecological flow at key sections and water quantity discharged into the ocean are added as the constraint conditions to generate optimal operation schemes that reflect ecological benefits. The case study of the Xiaolangdi Reservoir (XLDR) on the Yellow River, China shows that with this model, the multi-objective requirements of water supply, ecology, sediment transport, flood control, and power generation in the XLDR could be met synergistically by optimizing the average daily discharge of the reservoir. Although the generated ecological operation schemes consider the demand for wetland protection, the reservoir flood control, sediment transport and power generation were not affected, and the latter two even showed improvement. In addition, this model has stronger applicability for large reservoirs. In dry years, small and medium reservoirs require water transfer, water-saving, and other measures required to alleviate water shortage.

Multi-dimensional interest game between reservoir and city stakeholders in the Yellow River Basin: a case study of the lower reaches

Reservoirs in sediment-laden rivers can bring multiple benefits, and the calculation and redistribution of these considerable benefits are the premises to ensure the efficient operation of reservoirs. Firstly, the benefits of social economy, ecological environment, flood discharge, and sediment transport under the joint operation of reservoirs are uniformly measured based on the emergy theory. Secondly, the stakeholders are divided into reservoir and city groups. A two-tier gains allocation model is established based on the Nash bargaining model and multi-attribute decision making theory. Finally, taking the lower reaches of the Yellow River, Sanmenxia Reservoir, and Xiaolangdi Reservoir as cases, the multi-dimensional benefits of reservoirs under the two operation modes in the face of typical floods are calculated, and the gains are distributed among stakeholders. The results show that: (1) Although the overall benefit of the system is optimal under one scheduling mode, 7/17 of the stakeholders prefer another mode. (2) Comparing the two operation modes of the reservoir group, it is found that XLD and SMX can improve the overall benefit of 4.12E + 09yuan at the cost of their sediment discharge benefits of 3.08E + 09yuan and 2.82E + 06yuan. (3) After gains distribution, the profit of all stakeholders can be optimized to varying degrees. This study broadens the dimension of benefit accounting under the joint operation of cascade reservoirs and the category of stakeholders in the gain allocation, which is conducive to promoting the ecological protection and sustainable development of sediment-laden rivers.

Downdrift Port Siltation Adjacent to a River Mouth: Effects of Mesotidal Conditions and Typhoon

The Zhuoshui River has one of the highest sediment yields in the world. The riverine sediment may have been transported away from the river mouth by strong tidal currents and deposited in a navigational channel and a harbor basin south of the Zhuoshui River. This study describes the dispersal of riverine sediments in mesotidal conditions, including transport processes of sediments via river plumes, initial deposition, resuspension, and long-term net accumulation. Our results revealed that the distribution of suspended sediment concentration (SSC) and the transport process of the river plume was markedly modulated by tidal currents in a north–south direction. Under high-discharge conditions, energetic winds and ocean currents interrupted the offshore propagation of the sediment-laden river plume with a high SSC to the ocean. The plume, induced by typhoon floods, was either propagated northward due to the Coriolis effect or was deposited near the river mouth. The sediments deposited within the inner shelf were resuspended by intensive tidal currents and transported through southward residual circulations to the navigation channel south of the river mouth.

Human disturbances dominated the unprecedentedly high frequency of Yellow River flood over the last millennium.

A warming climate may increase flood hazard through boosting the global hydrological cycle. However, human impact through modifications to the river and its catchment is not well quantified. Here, we show a 12,000-year-long record of Yellow River flood events by synthesizing sedimentary and documentary data of levee overtops and breaches. Our result reveals that flood events in the Yellow River basin became almost an order of magnitude more frequent during the last millennium than the middle Holocene and 81±6% of the increased flood frequency can be ascribed to anthropogenic disturbances. Our findings not only shed light on the long-term dynamics of flood hazards in this world's most sediment-laden river but also inform policy of sustainable management of large rivers under anthropogenic stress elsewhere.

Design and verification of Francis turbine working in sand laden hydro-power plant

Sand erosion is usually severe for hydraulic turbine operated in sediment-laden river hydro-power plant. Continuous erosion and abrasion in hydro-turbine components not only deteriorate the turbine performance but also bring frequent maintenance work. Thus, special attentions should be paid to anti-erosion performance besides the efficiency and stability during the hydraulic design stage. In this paper, the performances of a prototype Francis turbine used for a high head heavy sediment power station were investigated by reducing the rotational speed and using splitter runner. The hydraulic performance, anti-erosion characteristics and cavitation performance were focused and analyzed. The results proved that the velocity in the runner can be effectively reduced by lower the rotational speed, but the rotational speed reduction was also limited by the efficiency and velocity near the guide vane. The splitter runner can significantly improve the disorder flow in runner by re-distributing the velocity field. The erosion resistance of guide vane can be improved by increasing the pitch diameter of the guide vane appropriately. 3100 h of operation after commissioning further confirmed the anti-erosion and stability performance of the designed Francis turbine. This research provide a good reference for the Francis turbine design operated in heavy sediment hydro-power plant.

Geomorphologic evolution of the shallow-buried abandoned Yellow River delta during the last 2000 years

Different from the continuous development of many river deltas since the major Holocene transgression, the modern Yellow River delta (YRD) remained for nearly 1000 years (from 893 AD to 1855 AD) in an abandonment state, until after 1855 AD when it was buried after the Yellow River entered the sea via Lijin. In this study we used optically stimulated luminescence (OSL) dating and grain size and sedimentary facies analysis of four borehole cores, combined with an analysis of landform morphology, to reconstruct the history of the ancient abandoned YRD. The results indicate that after the delta was abandoned due to the reduced sediment supply by the Yellow River in 893 AD, a sandy coast developed under the influence of wave erosion, and offshore shell ridges were formed beyond the coastline. During the interval from the Medieval Warm Period (MWP) to the Little Ice Age (LIA), driven by climate change and storm surges, the shell ridges migrated laterally, widened and rose, while sediment accumulation in the landward-side interfluvial floodplains was relatively weak. This configuration subsequently constituted a coastal highland – plain depression system. After 1077 AD, this system, together with the abandoned delta, was eroded by the Daqing River estuary. After 1855 AD, the abandoned delta landform system was completely buried by Yellow River sediments, and the wave-controlled sandy coast was transformed to a tide-controlled silt-mud coast. We summarize these findings in the form of a geomorphic model of the evolution of the abandoned delta from the MWP to the LIA. Overall, our results highlight the geomorphic effects of the sediment-laden river delta and the response of the abandoned delta geomorphic system on the millennial timescale, and they provide a theoretical foundation for predicting the geomorphic evolution of a major river delta on different timescales, against the background of global change.

River pattern discriminant method based on Rough Set theory

Study regionThe Yellow River located in the north of China, the most hyper-concentrated sediment-laden rivers in the world, is featured by complicated spatiotemporal variation of river patterns. Study focusRiver patterns contribute to comprehending the spatial morphological evolution of rivers associated with hydrological processes. However, it is still a challenge to effectively discriminate different river patterns due to the dynamics and variability of rivers. A solution is proposed to discriminate river patterns based on Rough Set theory via a holistic synthesis of multi-dimensional morphological information. First, a hierarchical structure integrating the boundary and the interior was suggested to maximally describe the morphological feature of river patterns. Rough Set theory was applied to select the main feature factors from multiple geometric indexes and landscape pattern indexes. Finally, river pattern discriminant rules were generated based on the reduced feature subsets. New hydrological insights for the regionResults demonstrate that 81 discriminant rules efficiently express the morphological feature of four river patterns. Compared with several competitive machine learning methods, river pattern discriminant rules display good performance, with the advantages of interpretability, simple modelling, and fewer training samples. Furthermore, the established discriminant rules of river patterns have achieved an accuracy of 98.63% in the application of the Lower Yellow River, which is expected to analyse the spatiotemporal evolution and geomorphological processes of different river patterns.

A review on synergy of cavitation and sediment erosion in hydraulic machinery

The synergy of cavitation and sediment erosion is the most severe destruction in hydraulic machinery in sediment-laden rivers, and currently the physics and mechanism are still lack of understanding. The synergy effects of cavitation and sediment erosion not only reduce the efficiency and life of hydraulic machinery but also cause costs in operation and maintenance. With the rapid development of renewable clean energy and the transformation of water resources, an increasing number of new hydropower stations and water diversion projects are currently planned or under construction, where most of them are in sediment-laden rivers. In the present paper, the research work, including theory, experiment, and simulation, in this field carried out by various investigators are presented and discussed. Physical mechanisms involved in the synergy of cavitation and sediment erosion which is responsible for material damage as investigated by researchers have also been discussed, and would help to identify gaps for future studies.

Sustainable sediment management for sustainable use of reservoirs

Sustainable sediment management for sustainable use of reservoirs