Increase In Sediment Concentration Research Articles

Twin Satellites HY-1C/D Reveal the Local Details of Astronomical Tide Flooding into the Qiantang River, China

This article extracts the Qiantang River tidal bore, analyzing the water environment characteristics in front of the tidal line of the Qiantang River tidal bore and behind it. The Qiantang River tidal bore Index (QRI) was established using HY-1C, HY-1D, and Gao Fen-1 wide field-of-view (GF-1 WFV) satellite data to precisely determine the location and details of the Qiantang River tidal bore. Comparative analyses of the changes on the two sides of the Qiantang River tidal bore were conducted. The results indicate the following: (1) QRI enhances the visibility of tidal bore lines, accentuating their contrast with the surrounding river water, resulting in a more vivid character. QRI proves to be an effective extraction method, with potential applicability to similar tidal lines in different regions. (2) Observable roughness changes occur at the tidal bore location, with smoother surface textures observed in front of the tidal line compared to those behind it. There is a discernible increase in suspended sediment concentration (SSC) as the tidal bore passes through. (3) This study reveals the mechanism of water environment change induced by the Qiantang River tidal bore, emphasizing its significance in promoting vertical water body exchange as well as scouring the bottom sediments. This effect increases SSC and surface roughness.

Study on strengthening of sulfide tailings high-efficiency solid-liquid separation using water reducing admixtures

The global focus on refined mineral processing and environmental protection has led to stricter requirements for tailings disposal processes. The complex composition and chemical environment of tailings pose challenges in sedimentation and pipeline transportation. This research developed a new additive that is suitable for disposing of copper-lead-zinc sulfide tailings. This additive not only improves sedimentation efficiency and concentration, but also enhances the flowability of high-concentration slurry. This study investigated the effects of four typical water reducing admixtures on the settling and rheological properties of tailings. However, the combination of lignin/PCE and NPAM had a synergistic effect, further improving settling and rheological performance. The addition of PCE increased settling rate by over 2 times, increased sediment concentration by 6.71%, and significantly reduced slurry viscosity and yield stress. The study also used FBRM to analyze the changes in particle/floc size distribution over time. The results showed that the addition of PCE captured more fine particles during flocculation and formed larger flocs. These findings can be used as a reference for the use and optimization of additives in tailings disposal engineering.

Modeling sediment concentrations and loads for two small agricultural watersheds in Prince-Edward-Island (Canada): present conditions and a future scenario

The degradation of soils and its detrimental consequences on aquatic environments is an important research topic in agricultural regions such as Prince Edward Island (PEI, Canada). Enhanced information related to suspended sediments in watercourses can serve as an effective decision-making tool in agricultural land management. This study aims to compare flow, suspended sediment concentrations (SSC), and loads using the Soil and Water Assessment Tool (SWAT) in two watersheds in Prince Edward Island (PEI). The final investigations will focus on the potential variations in hydrological and sedimentary values in the future using a relatively pessimistic climate change scenario. Finally, the projected sediment concentrations and loads will be analyzed, considering their potential impacts on ecosystems. Water level and turbidity were recorded using two water level loggers and two optical backscatter sensors (OBS) deployed in the Tuplin Creek and Spring Valley watersheds. These instruments continuously recorded suspended sediments and flow data from June 2021 to September 2022. The data were used to manually calibrate the hydrological and suspended sediment models. The understanding of sediment loads and the benefits of proposed changes to agricultural practices can be tested with the SWAT model, as it incorporates a land use index that varies spatially and temporally. Calibration and validation of both the hydrological and sediment models were satisfactory, with Kling-Gupta Efficiency coefficients varying between 0.51 and 0.73 and Nash-Sutcliffe coefficients varying between 0.61 and 0.73 respectively, indicating successful simulation of both variables in an agricultural context in spite of relatively short calibration and validation periods. Under the selected climate change scenario (RCP 8.5), daily flows and suspended sediment concentrations were simulated until 2,100, showing a slight increase in the average suspended sediment concentration (CSS). For Tuplin Creek, extremely high sediment peaks (>1,500 mg/L) could become significantly more frequent, potentially causing more frequent and severe ecosystem disturbances according to the simulations.

A strategy for modelling sediment distribution along slope lengths of an ephemeral gully through the simulated scouring experiments

Accurately describing the soil erosion process is crucial for improving the accuracy of existing simulation models of ephemeral gully erosion. However, a laboratory experimental strategy for simulating sediment distribution along slope lengths of an ephemeral gully is lacking. This limitation greatly hinders the development of simulation models for ephemeral gully erosion. In this study, we constructed six soil flumes with 12 m in length, 0.1 m in width, and 0.5 m in depth, which were filled with cultivated loess soils. Four flow rates (5.33, 10.67, 21.33, and 42.67 × 10−3 m3 s−1 m−1), four slope gradients (5°, 10°, 15°, and 20°), and six gully lengths (2, 4, 6, 8, 10 and 12 m) were adopted to perform a series of laboratory scouring experiments. The measured sediment concentrations at the outlet ranged from 23.39 kg m−3 to 534.60 kg m−3. The trend of exponential increase in sediment concentrations along slope lengths of an ephemeral gully was similar to that observed in a rill. According to the fitting equation, the maximum sediment concentrations (Ae) ranged from 358.05 kg m−3 to 910.88 kg m−3. The attenuation coefficients (Be) indicated the rate of increase in sediment load with slope length, which ranged from 0.042 m−1 to 0.185 m−1. By combining the measured sediment loads along the slope length (8 m) with the sediment transport capacity, the sediment distribution along slope lengths of an ephemeral gully could be accurately quantified. Moreover, the results confirmed that a flume with a short slope length (4/6 m) could effectively determine the sediment distribution along slope lengths at gentle slope of 5° and 10°. However, a minimum length of 8 m was advisable at steep slope of 15° and 20°. In summary, our experimental strategy provides an efficient method for determining the sediment distribution along slope lengths of an ephemeral gully.

LUSI sediment characteristics and its distribution pathway in the porong river

The Porong River has been utilized to remove mud from the Sidoarjo mud volcano through the spillway since September 2006. The existence of Sidoarjo Mud (LUSI) in the river adds to the source of sediment, resulting in high-capacity sediment transport and increased sediment concentration, affecting the ecosystem and river capacity. To determine sediment deposition around the LUSI outfall area, this study analyzed nine sections to obtain bed material data. Each section has three observation points to collect material samples to produce comprehensive data. The cross-section stretches from the LUSI outfall area downstream, with a cross-sectional distance of 1 km, so the total length is 9.5 km. The study found clear changes in sediment composition across the analyzed area, with sand dominating the sediment profile in the upper reaches of the LUSI outfall. Sand dominance is due to local scour on the bridge pillars and groundsills on the river bed. In addition, these muds show characteristic depositional pathways, concentrated mainly along the river banks. This study highlights the importance of understanding sediment dynamics, influenced by variations in sediment sources, in disaster management and mitigation.

Deep-sea mining: using hyperbaric conditions to study the impact of sediment plumes in the subtidal clam Spisula solida.

With the growing interest to exploit mineral resources in the deep-sea, there is the need to establish guidelines and frameworks to support hazard and risk assessment schemes. The present study used a subtidal species of filter-feeding bivalve, the clam Spisula solida, as a proxy to better understand the impacts of sediment plumes in marine organisms under hyperbaric conditions. Four concentrations of suspended sediments (0g/L, 1g/L, 2g/L, and 4g/L) were used in a mixture with different grain sizes at 4 Bar for 96h. Functional (filtration rate-FR) and biochemical endpoints (catalase-CAT, glutathione s-transferase-GST, and lipid peroxidation-LPO) were analyzed in the gonads, digestive gland, and gills of S. solida after a 96-h exposure at 4 Bar (the natural limit of the species vertical distribution). The FR showed a decreasing trend with the increasing sediment concentrations (significant effects at 2 and 4g/L). Additionally, significant changes were observed for some of the tested oxidative stress biomarkers, which were concentration and tissue-dependent, i.e., CAT activity was significantly elevated in gills (1g/L treatment), and GST was decreased in digestive gland (1g/L treatment). Overall, the results show that suspended sediments, at 2 and 4g/L, have negative functional impacts in the bivalve S. solida providing additional insights to improve hazard assessment of deep-sea mining. These findings represent a step forward to ensure the mitigation of the potential negative effects of deep-sea resource exploitation.

Study on the critical sediment concentration determining the optimal transport capability of submarine sediment flows with different particle size composition

Submarine sediment flows is one of the main means for transporting sediment to the deep sea, often traveling long-distance and transporting significant volumes of sediment for tens or even hundreds of kilometers. Its strong destructive force often causes serious damage to submarine utilities on its course of movement. The sediment concentration of the sediment flow determines its density difference with the ambient seawater, and this density difference determines the flow ability of the sediment flow, and thus affects the final deposition locations of the transported sediment. In this paper, sediment flows of different sediment concentration with various silt and clay weight ratios (referred to as silt/clay ratio) are studied using flume tests. Our test results indicate that there is a critical sediment concentration at which sediment flows travel the fastest for a specific sediment composition. The critical sediment concentrations and their corresponding maximum velocities for each of the four silt/clay ratios are obtained. The results further indicate that the clay content is linearly negatively correlated with the critical sediment concentration. As the sediment concentration increases, the flow behaviors of sediment flows transform from the flow state to the collapsed state, and the fluid properties of the two turbid suspensions with changing flow behaviors are both Bingham fluids. Additionally, this paper also provides a microscopic explanation of the above-mentioned results by analyzing the arrangement of particles within the sediment flow.

A two-dimensional double layer-averaged model of hyperconcentrated turbidity currents with non-Newtonian rheology

Hyperconcentrated turbidity currents typically display non-Newtonian characteristics that influence sediment transport and morphological evolution in alluvial rivers. However, hydro-sediment-morphological processes involving hyperconcentrated turbidity currents are poorly understood, with little known about the effect of the non-Newtonian rheology. The current paper extends a recent two-dimensional double layer-averaged model to incorporate non-Newtonian constitutive relations. The extended model is benchmarked against experimental and numerical data for cases including subaerial mud flow, subaqueous debris flow, and reservoir turbidity currents. The computational results agree well with observations for the subaerial mud flow and independent numerical simulations of subaqueous debris flow. Differences between the non-Newtonian and Newtonian model results become more pronounced in terms of propagation distance and sediment transport rate as sediment concentration increases. The model is then applied to turbidity currents in the Guxian Reservoir planned for middle Yellow River, China, which connects to a tributary featuring hyperconcentrated sediment-laden flow. The non-Newtonian model predicts slower propagation of turbidity currents and more significant bed aggradation at the confluence between the tributary Wuding River and the Yellow River in the reservoir than its Newtonian counterpart. This difference in model performance could be of considerable importance when optimizing reservoir operation schemes.

Changeability of runoff and soil loss from inclined mid-sized plots under simulated upward wind-driven rain

The present study investigated the interaction of wind and rain (WDR) on splash and interril erosions under laboratory conditions. The corresponding experiments were carried out with rainfall intensity of 50 mm h−1 with a duration of 30 min under no-wind control conditions and two wind velocities viz., 3 and 6 m s−1 at a slope of 12%. The study was conducted on sandy-loam soil from summer rangelands of the Northern Alborz Mountain in Iran. The soil collected was transported to the Rainfall and Erosion Simulation Laboratory. The prepared 6 × 1 m-plots were concurrent with the simulation of the WDR. Moreover, three splash cups were used to measure splash erosion, and each cup was placed on the soil surface at distances of 1.5, 3.0, and 4.5 m from the plot outlet. The results displayed the significant effects of wind (P < 0.01) on runoff generation and soil erosion components. Therefore, the mean runoff and runoff coefficient decreased while increasing wind velocity increased sediment concentration and soil loss. The mean runoff volume and coefficient were 103.48, 94.62, and 88.82 L and 94.43, 87.23, and 81.62 % at wind velocities of 0, 3, and 6 m s−1, respectively. In addition, the mean soil loss and sediment concentration were 414.94, 1057.47, and 1375.48 g; and 31.35, 156.31, and 303.75 g L−1; at 0, 3, and 6 m s−1 wind velocities, respectively. Besides, the mean net splash increased significantly with increasing wind velocity, from 9.58, 14.93, and 18.63 g, respectively, as wind velocity changed from 0 to 3 and then 6 m s−1. It has been proven that WDR soil erosion was higher than no-wind rain. This research could increase soil managers' awareness of solution strategies.

Rapid fluvial remobilization of sediments deposited by the 2021 Chamoli disaster, Indian Himalaya

Abstract High-magnitude mass flows can have a pervasive geomorphological legacy, yet the short-term response of valley floors to such intense disturbances is poorly known and poses significant observational challenges in unstable landscapes. We combined satellite remote sensing, numerical modeling, and field observations to reconstruct the short-term geomorphological response of river channels directly affected by the 7 February 2021 ice-rock avalanche–debris flow in Chamoli district, Uttarakhand, India. The flow deposited 10.4 ± 1.6 Mm3 of sediment within the first 30 km and in places reset the channel floor to a zero-state condition, requiring complete fluvial re-establishment. In the 12 months post-event, 7.0 ± 1.5 Mm3 (67.2%) of the deposit volume was removed along a 30-km-long domain and the median erosion rate was 2.3 ± 1.1 m a–1. Most sediment was removed by pre-monsoon and monsoon river flows, which conveyed bedload waves traveling at 0.1–0.3 km day–1 and sustained order-of-magnitude increases in suspended sediment concentrations as far as 85 km from the event source. Our findings characterize a high-mountain fluvial cascade with a short relaxation time and high resilience to a high-magnitude geomorphological perturbation. This system response has wider implications, notably for water quality and downstream hydropower projects, which may be disrupted by elevated bedload and suspended sediment transport.

Effects of sediment properties on abrasive erosion of a centrifugal pump

The presence of sediment particles in flows of centrifugal pumps significantly enhances the erosion rate which leads to reduced efficiency and shortened operational life of the pump. To investigate the performance and wear characteristics of a centrifugal slurry pump, the Eulerian-Lagrangian approach has been adopted in this study under various slurry flow conditions. The pump performance decreased whereas the average erosion rate of impeller blades and volute casing increased linearly with an increase in sediment concentration, according to the results of numerical simulations. The particle size distribution, from mono-sized distribution to a very broad distribution, reduced the average erosion rate by 20% on the impeller surface. In contrast, the erosion rate of the volute surface increases by 30% from mono-sized distribution to very broad distribution. Angular particles yield a higher rate of erosion for both blades and volutes as compared with spherical particles.

Confluence morphodynamics in mountain rivers in response to intense tributary bedload input

AbstractCoarse sediment transported by steep mountain tributaries during channelized flash flood events with intense bed load transport poses a significant threat to life, property, and infrastructure. Intense bedload transport occurring in tributary channels and insufficient transport capacity of the main channel flow can provoke flooding at the confluence. Deposition in the confluence can lead to overbank flooding and sedimentation into adjacent settlement areas. Extensive research has been carried out investigating lowland river confluences, where it has been determined that the confluence angle and discharge ratio have the most significant influence on channel morphology and hydraulics. However, there is a lack of information concerning confluences with low width and discharge ratios, high sediment concentrations, and gradients, typically found in steep mountain channels. This study presents results from large‐scale laboratory experiments coupled with numerical modelling with a standardized river confluence geometry. Bedload transport capacities, the shape, and volume of the deposition zone in the confluence, bedload dispersion characteristics, hydraulic and morphological dynamics, and spatial boundaries were analysed for various discharges and sediment concentrations. The confluence angle was 90°, sediment concentration was 5%, 7.5%, and 10%, and the discharge ratio was 0.1. The model was designed to accommodate scale factors of 20–40. With this configuration, a set of experiments based on steady‐state hydraulic conditions was accomplished. Results show that when the discharge ratio and confluence angle are constant, different morphologies occur, indicating that in addition to the confluence angle and the discharge ratio, the sediment concentration, flow velocity, and unit stream power significantly impact both hydraulic and morphologic zones in the confluences of mountain rivers. Additionally, backwater effects upstream of the confluence, and sedimentation in the tributary channel increases with increasing sediment concentration, which not only influences confluence morphodynamics and hydraulics but also the potential for overbanking of both channels.

A trapping capacity constraint model for sediment transport in vegetative filter strips (VFS) on sloping surfaces

AbstractMost current modelling practices for sediment trapping in vegetative filter strips (VFS) assumed a constant sediment trapping efficiency of VFS, while, in practice, it was found to decrease greatly with the increasing trapped sediment amount in VFS (decreasing sediment trapping capacity of VFS). To account for this impact, a widely used VFS sediment transport module was modified to consider the changing sediment trapping capacity of VFS, which was expressed by a power‐law relationship with the inflow discharge, sediment concentration, slope gradient, and antecedent deposition amount. An integrated model that coupled a slope infiltration‐runoff module and the modified sediment transport module was then developed to simulate hydrology and suspended sediment transport in VFS on sloping surface. The model is calibrated and validated by 18 VFS experiments with different inflow, sediment, and slope conditions from Luo et al. (Science of the Total Environment, 725, 138361, 2020). Good agreements between observed and simulated runoff and sediment transport processes were found for nearly all cases. Due to the impact of changing sediment trapping capacity of VFS, the trapped sediment amount and the sediment transport rate of outflow varies greatly in space and time. With the increase of inflow discharge, sediment concentration, and slope gradient, the overall sediment trapping efficiency of VFS tends to decrease greatly and then remains almost unchanged. The comparison between proposed model and original physically based model shows that neglecting the impacts of changing sediment trapping capacity of VFS would lead to a constant and overly large sediment trapping efficiency of VFS, especially on steep slopes. Moreover, comparing with the empirical expression, the model with well‐founded theory can provide higher fidelity and more detailed results. Thus, the modelling framework is expected to provide a more effective approach for VFS assessment and maintenance in local or watershed scale.

An assessment of South American sediment fluxes under climate changes

Climate change can affect all levels of society and the planet. Recent studies have shown its effects on sediment fluxes in several locations worldwide, which can impact ecosystems and infrastructure such as reservoirs. In this study, we focused on simulating sediment fluxes using projections of future climate change for South America (SA), a continent with a high sediment transport rate to the oceans. Here, we used four climate change data yielded by the Eta Regional Climate Model: Eta-BESM, Eta-CanESM2, Eta-HadGEM2-ES, and Eta-MIROC5. In addition, it was evaluated the RCP4.5 greenhouse gas emissions scenario from CMIP5, which represents a moderate scenario. Climate change data between 1961 and 1995 (past) and 2021 and 2055 (future) were used to simulate and compare changes that may occur in water and sediment fluxes using the hydrological-hydrodynamic and sediment model MGB-SED AS. The Eta climate projections provided input data to MGB-SED AS model, such as precipitation, air surface temperature, incident solar radiation, relative humidity, wind speed, and atmospheric pressure. Our results showed sediment fluxes are expected to reduce (increase) in north-central (south-central) SA. While a sediment transport (QST) increase >30 % might occur, a 28 % decrease is expected to occur in the water discharge for the main SA basins. The most significant QST reductions were estimated for the Doce (−54 %), Tocantins (−49 %), and Xingu (−34 %) rivers, while the most significant increases were estimated for the Upper Paraná (409 %), Juruá (46 %), and Uruguay (40 %) rivers. We also observed that different climate change signals over large basins can impact the river water composition, which could lead to a new composition of the Amazon basin waters in the future, accompanied by a significant increase in sediment concentration.

Regime of fluvial phosphorus constituted by sediment

Phosphorus (P) is a crucial macronutrient, and recently a venture agent of pollutant, in aquatic systems worldwide. Most of P circulates with sediment through rivers, and the relationship between P and sediment is the basis for understanding the biogeochemical processes in rivers. Although studies of fluvial P have been carried out at specific sites and for particular problems, the general regime by which sediment affects P recirculation still warrants attention. In this study, a series of water samples were collected from six different rivers in China whose sediment concentration and size distribution vary widely and their P properties were analyzed in the laboratory. From this analysis of field samples, a highly consistent comet shaped pattern of sediment effects on P is revealed, i.e., generally the range of the concentration of total P has a diverge-converge trend as the sediment concentration increases. It is further supported by examining the strictly composed samples from P adsorption experiments. Furthermore, case analyses were performed on the basis of the above relationships to illustrate the impact of sediment on P cycling in rivers. The results can infer the following: 1) There is a strong positive correlation between total P and sediment concentration, indicating that sediment is a crucial agent in the movement and fate of P. 2) The negative correlation between dissolved P and sediment concentration indicates a buffering effect of sediment, especially fine sediment, on dissolved P, interpreting the intricate phenomena of increased dissolved P concentration caused by sediment reduction. Hence, natural sediment has the prevailing advantage in moderating the water quality of rivers, which is directly relevant to mitigating the present pollution and eutrophication of waters. 3) River damming causes a P blockage tendency, altering the fluvial nourishment to contamination in the river.

Effect of sediment particles on the velocity profile of sediment–water mixtures in open-channel flow

The presence of sediment particles in open-channel flow has an important effect on turbulence; thus, an empirical, turbulent eddy viscosity formula was established for application in the limit for low concentrations. The current study establishes a theoretical relation for the mixture viscosity based on the two-phase mixture model. The percentage contribution of the three mechanisms of mixture viscosity, namely, fluid turbulence (FT), particle turbulence (PT), and inter-particle collisions (IPCs), was calculated under different conditions. The study results indicate that the contribution of FT is dominant, whereas those of PT and IPCs are not significant when the particle inertia (PI) is small, suggesting that the movement of sediment-laden flows is mainly controlled by the fluid properties. The effects of PT and IPCs increase with increases in sediment concentration and PI. Specifically, the effect of collisions among particles generally becomes dominant near the bed surface. A good agreement between the calculated velocity profile of the mixture and available experimental data for large particle sizes and high concentrations proves that the proposed relation for mixture viscosity is more reasonable than the previous empirical relation owing to the consideration of the effects of PT and IPCs, and, thus, can be applied to both dilute and dense suspensions.

Stream nitrogen uptake associated with suspended sediments: A microcosm study

Despite significant advances in our understanding of nitrogen (N) removal pathways along river networks, the role of water column processes remains largely understudied. This knowledge gap not only limits our capacity to determine N transport and retention in mid-to-large rivers but also hampers our understanding of N removal processes in smaller streams during stormflow conditions, in which significant increases in suspended sediment concentrations (SSC) typically occur. High SSC in the water column can provide abundant substrate for microbial growth and water column N uptake. However, storms of different size mobilize different quantities of sediment of varying properties and sizes, which can ultimately modulate water column N uptake rates in the stream during stormflows. To assess water column N uptake associated with suspended sediment particles of different sources and sizes, we quantified assimilatory and dissimilatory N uptake rates in a set of microcosms representing a gradient of sediment properties (organic matter, N content, and microbial activity) and surface area (fine vs. coarse size) availability. Water column assimilatory uptake (Used) ranged from 12.7 to 187.8 µg N [g sediment]−1 d−1 across all sediment sources and size fractions, and was higher on average than denitrification rates (DNsed) in agricultural and stream bank sediments but not in streambed sediments (mean DNsed = 240.9 ± 99 µg·N [g sediment]−1·d−1). Sediment-bound C in suspended sediment varied among sediment sources and was directly related to Used rates, but not to DNsed rates, which were less predictable and more variable. Overall, our results showed a positive nonlinear relationship between water column N uptake and SSC, while indicating that water column N uptake may scale differently to SSC depending on sediment source, and to a lesser degree, particle size. Because low, moderate, and large storms can mobilize different quantities of sediment in the watershed of different sources and sizes, it is likely that storm size will ultimately modulate the contribution of water column uptake during storm events to whole-reach N retention.

HY-1C/D Reveals the Chlorophyll-a Concentration Distribution Details in the Intensive Islands’ Waters and Its Consistency with the Distribution of Fish Spawning Ground

Chlorophyll-a (Chl-a) change details derived from HY-1C/D images in the waters of the Zhoushan archipelago were analyzed. A new Chl-a inverse model was built based on the relationship between the in situ Chl-a and the combination of red, blue and green bands of the coastal zone imager (CZI). Chl-a as well as fishery resources were analyzed. The results showed the following. (1) The Chl-a concentration in the waters of the Zhoushan archipelago was mainly in the range of 0.5~6 μg/L. High Chl-a area distributed in the west side of the study area, with a value of 3.5~5.5 μg/L. The Chl-a concentration in the east side of the study area was relatively lower, with a value of 0.5~2 μg/L. Chl-a around the islands was higher than that in the area far away from the islands. In addition, Chl-a concentration increased obviously downstream of the island. (2) The spawning ground of many fish in the waters of the Zhoushan archipelago was abundant, and its spatial-temporal variation was consistent with the change of Chl-a. (3) The islands interacted with the current, inducing upwelling upstream and vortex streets downstream. The complex hydrodynamic environment promoted a vertical exchange of water bodies, thereby resulting in an increase in suspended sediment concentration, nutrients, Chl-a and attracting fish.

The influence of wind-induced sediment resuspension and migration on raw water turbidity in Lake Taihu, China.

Lake Taihu is an important drinking water source for cities in the Yangtze River Delta region, while the dramatic fluctuation in turbidity has caused severe problems for local waterwork management. The effects of sediment resuspension and migration on turbidity of water intake in a waterworks located in the south of Lake Taihu are studied. Because the sediment behavior induced by wind disturbance was believed to be the main factor for the matter, the effect of wind field on the hydrodynamics and sediment distribution of Lake Taihu was conducted based on a wind-driven numerical model. The obtained results indicate that wind direction was more influential on the structure of flow and wave fields, while wind speed contributed more to the field intensity. The suspended sediment concentration (SSC) of water intake area was most sensitive to onshore winds, which led to significant increase in suspended sediment concentration at 3m/s, while for alongshore winds, the incipient speed was 4m/s, and offshore winds were less influential. In addition, the suspended sediment of the water intake area was primarily migrated from other erosion regions rather than local suspended particles. A 7-h lag was found between SSC and the measured turbidity confirmed the lag effect of wind disturbance on turbidity change. The high consistency between the 2 series demonstrated the potential of this method to turbidity prediction when combined with the weather forecast technique.

An experimental insight into dynamic characteristics and wear of centrifugal pump handling multi-size particulate slurry

The river water has a high sand content and the characteristics of mixed distribution of sand particles with different diameters. The effect of sand particles on the dynamic characteristics and wear of centrifugal pumps is an important issue when handling particulate slurry. The objective of this work is to establish the effect of flow rate and sand volume concentration variation on pump energy performance, outlet pressure pulsation, pump body vibration, and pump impeller wear. Experiments were conducted in a pilot plant test rig with five flow rates and three particle concentrations based on multi-size particulate slurry. It was observed that the head and efficiency of the centrifugal pump decrease with the increase of sand concentration, whereas the effect of small sand concentration on the energy performance of the pump is weak. The larger the flow rate of centrifugal pump, the lower the pressure pulsation and vibration intensity of pump body, but the more serious the impeller wear. When the sediment concentration increases, the pressure pulsation at the pump outlet and the vibration intensity of the pump body increase, and the impeller wear is more serious. In addition, with the increase of pump operation time, the outlet of blade pressure surface, the middle area of blade suction surface and the outlet area of impeller back shroud passage are seriously worn, and the outlet of blade pressure surface is the most serious.