High Sediment Research Articles

CNF Dispersion Evaluation by Particle Size Distribution Measurement Using High Resolution Disc Centrifugal Sedimentation Method

CNFは一般的に湿式条件下で機械的処理によって微細化され，物性制御や有効活用する上で分散性の評価，とりわけ粒子径分布評価は重要である。粒子径分布計測には様々な原理，手法があるが幅広い分布を持つ粒子や異形粒子の測定は困難であり正確な分布が得られない課題がある。解繊の過程において様々な粒子径が同時に存在していることが多いCNFの評価においては，分解能の高い計測法が必要となる。ディスク遠心沈降方式粒子径分布測定法は，多くの計測法で用いられるフィッティングアルゴリズムを用いずに直接的に粒子を観測しており，さらに一旦各サイズごとに分級してから粒子を検出する方式のため分解能が非常に高い方式である。このディスク遠心沈降方式粒子径分布測定法を用いて処理回数の異なる6種類のCNF試料の粒子径分布の測定を行った。処理回数の少ない試料では，数十nmから数µmにかけて3つのピークをもつ分布が得られた。処理回数の増加につれて数µmのピークは消失し，数百nmのピークの減少が見られると同時に数十nmのピークは増加した。再現性もおおむね良好であった。ディスク遠心沈降方式粒子径分布測定法を用いることでCNFの物性制御や有効活用への利用が期待できる。

PS-R05-3: SEVERE GLOMERULAR MICROANGIOPATHY IN A PATIENT WITH NEPHROTIC SYNDROME FOLLOWING TAKAYASU ARTERITIS

Introduction: Takayasu arteritis (TA) is a large vessel inflammation that predominantly involves aorta and its main arteries. TA-caused kidney injury is known to be mainly due to renal artery stenosis. However, glomerulonephritis including membranous proliferative glomerulonephritis, focal segmental sclerosis, or crescentic nephritis has been histologically identified in some TA cases. Case description: A 69-year-old female presented with leg edema and refractory hypertension with nephrotic range proteinuria (17.0 g/gCr). She exhibited > 10 mmHg blood pressure discrepancy between left and right upper limbs and severe aortic regurgitation. Lab test showed high level of C-reactive protein and high erythrocyte sedimentation rate. Contrast-enhanced computed tomography identified wall thickening of the left subclavian artery, which led to the diagnosis of TA. Renal biopsy demonstrated that double basement membrane, enlarged subendothelial space, and mesangiolysis with no immunoglobulin deposition. Although azilsartan 40 mg QD and nifedipine 30 mg BID had been prescribed, systolic blood pressure (sBP) was still > 160 mmHg. Thus, while oral prednisolone was started to suppress TA-induced inflammation, azilsartan was replaced with sacubitril valsartan, an angiotensin receptor-neprilysin inhibitor (ARNI), for treating refractory hypertension. After a few weeks, sBP was decreased to 130 mmHg with sacubitril valsartan 200 mg QD and proteinuria was dramatically improved to 0.5 g/gCr. Discussion: TA commonly involves the renal artery, leading to stenosis and subsequent ischemic nephropathy. However, no stenosis and occlusion were observed in renal artery of this case. In addition, small vessel inflammation in the kidney such as vessel wall necrosis and immune cells infiltration around arterioles was not found. Serum levels of pro-inflammatory cytokines including vascular endothelial growth factor and interleukin-6, a well-known contributors for progression of TA-related inflammation, were within the normal range. The results indicate that TA-caused hypertension, but not vessel inflammation induced by TA, seems to play a pathological role for development of glomerular microangiopathy in this case. A previous study showed that 70% of TA patients presenting with glomerular lesion has severe hypertension and intimal thickening in renal arterioles was observed more frequently in TA patients presenting with glomerular lesion when compared to those without glomerulonephritis, which supports our hypothesis. In the present case, ARNI significantly reduced sBP which might directly contribute to the improvement of proteinuria. ARNI can be potent to control hypertension more effectively than conventional hypertensive agents in TA patients.

A Miocene Nannofossil Biostratigraphic Case Study: Alaminos Canyon Block 627 and Mississippi Canyon Block 555, and Sedimentation Rates in the Gulf of Mexico

The Miocene sediments of 2 deep—water boreholes from the northern Gulf of Mexico, from Alaminos Canyon (AC) Block 627 and Mississippi Canyon (MC) Block 555, have been biostratigraphically analyzed using calcareous nannofossils, revealing changes in sedimentation rates and depositional environments between these 2 areas. High nannofossil abundance values and low sedimentation rates generally recorded in the Alaminos Canyon region suggest a condensed section during much of the Miocene, associated with a basinal environment. Mississippi Canyon exhibits lower nannofossil abundance and higher sedimentation rates compared to Alaminos Canyon during the majority of the Miocene. Increased sediment volumes are largely attributed to input from the Mississippi River. Sedimentation rate was calculated for both sites. In the AC Block 627 borehole, sedimentation rate ranged from 13 to 107 m/million years (my), and in the MC Block 555 borehole, it varied from 11 to 914 m/my. One major anomaly was a low observed sedimentation rate in the lowest portion of the section at MC Block 555, in the interval defined between the extinctions of Triquetrorhabdulus carinatus and Dictyococcites bisectus. This may reflect a hiatus or possible fault which has shortened the section.

Avaliação da luminescência do traçador fluorescente quinino: aplicação localizada em águas de superfície

Abstract Fluorescent tracers have been widely used in hydrology. Recently, quinine started to be used as a fluorescent tracer for estimating the velocity of surface sheet flows over various soil surface conditions and environments. In the present work, the visibility of the fluorescent tracer (quinine) was assessed for various applications’ forms of the tracer (liquid, ice cube with quinine and soaked sponge). The brightness intensity of all tracer forms was estimated for different hydraulic conditions (hydrostatic, linear, and rotational flows) and for clear water, and water with medium and high suspended sediment loads. Results show that, when used as a flow velocity tracer, liquid quinine solution has to be applied carefully into the water and should better be used on sheet flows, shallow overland flows or shallow still waters. Its visibility in deep and muddy flows is insufficient for surface velocity estimations. The sponge soaked with quinine solution, which partially floats, is better visible in clear waters or low-medium suspended sediment loads, regardless of the water depth. However, for high turbulence and rotational flows, the soaked sponge sinks and is no longer visible. The ice cubes showed better visibility in all tested flow water depths and suspended sediment loads, although, in very shallow depths (of millimetres), ice cubes cannot be used because they might not follow adequately the fluid motion, which also applies to the sponge.

Temporal evolution of Pu and Cs sediment contamination in a seasonally stratified pond.

There remains a lack of knowledge regarding ecosystem transfer, transport processes, and mechanisms, which influence the long-term mobility of Pu-239 and Cs-137 in natural environments. Monitoring the distribution and migration of trace radioisotopes as ecosystem tracers has the potential to provide insight into the underlying mechanisms of geochemical cycles. This study investigated the distribution of anthropogenic radionuclides Pu-239 and Cs-137 along with total organic carbon, iron, and trace element in contaminated sediments of Pond B at the Savannah River Site (SRS). Pond B received reactor cooling water from 1961 to 1964, and trace amounts of Pu-239 and Cs-137 during operations. Our study collected sediment cores to determine concentrations of Pu-239, Cs-137, and major and minor elements in solid phase, pore water and an electrochemical method was used on wet cores to determine dissolved elemental concentrations. More than 50 years after deposition, Pu-239 and Cs-137 in sediments are primarily located in the upper 5 cm in area where deposition of particulate-bound contaminants was prevalent and located between 5 and 10 cm in areas of high sedimentation, showing a limited migration of Pu-239 and Cs-137. A Factor analysis demonstrated different sediment facies across the pond resulting in a range of geochemical processes controlling accumulation of Pu and Cs. Highest concentrations appear to be controlled by particulate input from the influent canal, dominated by clay, silt, and sand minerals bearing Fe. Elevated Pu-239 in the sediments were observed in areas with high organic matter and higher deposition rate relative to the Pond B system near the outlet indicating strong association of Pu with OM and particulates. Therefore, organic matter cycling likely plays a role in Pu redistribution between sediment and overlying pond water, and deposition in organic rich sediments accumulating near the outlet. Though Pu appears to have been distributed throughout the pond, Cs-137 concentrations remained the highest near the influent canal.

Pulse-Doppler radar measurements of debris flows: High-resolution monitoring of surge dynamics from two events in the Gadria Creek (Italy)

As a consequence of their spontaneous occurrence, and frequent formation of multiple surges with high sediment loads, debris flows are considered one of the most hazardous gravity-driven mass movements in montane regions. Field measurements of surface velocities are an essential link in the chain of understanding fundamental process dynamics and applied protection against debris flows. In order to measure the velocities of multiple consecutive surges within a single debris-flow event, a PD radar (pulse-Doppler high-frequency radar) sensor for high-resolution real-time debris-flow monitoring has been developed. In this contribution we present PD radar measurements of two debris flows, that occurred at the Gadria creek in Italy on July 26, 2019, and August 10, 2020, over a torrent length of 250 meters. We record over 55 high-amplitude surges that overlap and superimpose at the front of the debris flow, but also subsequently throughout the debris-flow body. Our results demonstrate applicability of a PD radar for debris-flow monitoring and serve as a data source for modelling surge dynamics in debris flows.

The effect of channel geometry and check dam location on sediment transport discharge in the Kuranji River

Rivers as infrastructure carry water from upstream to downstream to meet the water needs of communities along the river and as drainage. Therefore, it is necessary to maintain the stability of the river from erosion and sedimentation. Changes in river geometry are mostly caused by the high intensity of rainfall in the upstream section. This causes the geometry to change easily, many bends are found, river embankments collapse, and the slope and flow of the river change suddenly. As a result, water will wash away sediment from upstream to downstream with high sediment discharge. However, the sediment rate/discharge can be reduced by building a check dam, but it needs the right location so that the construction of the check dam is effective and the river flow is stable. Research using HEC-RAS has been carried out at the location of the middle section of the Kuranji River, where simulating three check dam locations shows that the reduction in sediment discharge is very effective, but other places are still the same as without the check dam. Therefore, it is recommended to build check dam series and groundsills at narrowing locations and strengthen river banks at Sta. 16 to Sta. 32.

Application of Delft3D computational model to estimate the influence of El Bala run-of-the-river dam on the morphological activity of Beni River, Bolivia

Beni river is an important tributary in the Amazon basin. There, the Bolivian government decided the construction of a two-dam cascade hydropower system, including Chepete dam and El Bala run-of-the-river dam. The main concern is the high sediment transport in Beni river. Then, the aim of the research is the application of Delft3D model to estimate the influence of El Bala run-of-the-river dam on the sediment transport and morphological activity of Beni river. The model was calibrated for natural conditions based on ADCP data and sediment transport measurements collected from the river. The implemented model was able to reproduce hydrodynamics and sediment transport in natural conditions. Hence, several scenarios were tested. A hydrodynamic and morphological model was set to test the influence of the dam on the river for hydrodynamics, sedimentation and erosion processes in Beni river. Results show that Delft3D performed very well in modelling sedimentation and erosion processes in Beni river, the model was able to predict the expected erosion process due to the presence of Chepete dam, upstream of El Bala, which retains the sediment load of Beni river affecting the morpho-dynamics of the river. Additionally, the model was able to predict a sedimentation in the reservoir.

Improvement of the well cementing technology, increasing the reliability of the annule isolation and preserving the permeability of the reservoir

The article presents measures to improve the quality of cementing the production string of high-performance wells. The relevance of the proposed technological solutions is substantiated. The results of experimental studies of the installation simulating the processes occurring during the thickening of the cement slurry under the action of gravitational forces are presented. An algorithm for creating overpressure on the wellhead during fastening of the production string is proposed. The compositions of process fluids are described, which increase the reliability of the annular space isolation and preserve the permeability of the reservoir, and provide the main data on the results of their laboratory studies. For cementing the annular space of the production string, the composition of the expanding cement slurry has been developed and the procedure for its preparation has been established. The proposed solution has low water separation and high sedimentation resistance; has adjustable rheological parameters. Cement stone is characterized by low gas permeability and high strength properties.

Improvement of the well cementing technology

The article presents measures to improve the quality of cementing the production string of high-performance wells. The relevance of the proposed technological solutions is substantiated. The results of experimental studies of the installation simulating the processes occurring during the thickening of the cement slurry under the action of gravitational forces are presented. An algorithm for creating overpressure on the wellhead during fastening of the production string is proposed. The compositions of process fluids are described, which increase the reliability of the annular space isolation and preserve the permeability of the reservoir, and provide the main data on the results of their laboratory studies. For cementing the annular space of the production string, the composition of the expanding cement slurry has been developed and the procedure for its preparation has been established. The proposed solution has low water separation and high sedimentation resistance; has adjustable rheological parameters. Cement stone is characterized by low gas permeability and high strength properties.

Elevated sedimentation of clastic matter in pelagic Panthalassa during the early Olenekian

AbstractThe end‐Permian mass extinction is thought to have greatly altered biogeochemical cycles. The absence of chert and dominance of claystone in low‐latitude pelagic deep‐sea sedimentary sequences of Early Triassic Panthalassa (the deep‐sea chert gap) has been believed to record radiolarian die‐off and consequent decline in biogenic silica production. However, recent studies showed that the upper portion of the deep‐sea chert gap has sedimentation rates higher than bedded chert, meaning that increased clastic inputs, rather than decreased biogenic silica inputs, resulted in the anomalous lithology. In this study, we focus on the Akkamori‐2 section, which preserves a rare sedimentary sequence spanning a large part of the lower portion of the claystone of the deep‐sea chert gap. We obtained conodont fossils that allow correlation with sections in South China that have numerous dated tuffs. By projecting the dates of the tuffs to our measured sections, we show that sedimentation rates of the lower portion of the deep‐sea chert gap is also higher than bedded chert. Hence, most of the deep‐sea chert gap was formed under increased clastic inputs, which likely records disturbance in the terrestrial landscape, probably aridification and/or increased seasonality in arid areas, that lead to elevated dust flux to the pelagic ocean. On the other hand, the idea that the deep‐sea chert gap records lingering effects of the mass extinction event on radiolarians cannot explain the high sedimentation rates of the deep‐sea chert gap. This previously favored scenario needs to be reconsidered, taking into account the burial efficiency of biogenic silica in the Early Triassic ocean, and also effects of increased clay deposition on preservation of radiolarians.

Construction of a hollow MOF with high sedimentation performance and co-immobilization of multiple-enzymes for preparing rare ginsenoside CK

1. Sna&β-G@H-Cu-BDC biocomposite was synthesized via the hydrogel-template method with larger size. 2. Sna and β-G were co-immobilized in the hollow Cu-BDC MOF to produce the rare ginsenoside CK with cascade catalysis. 3. The Sna&β-G@H-Cu-BDC biocomposite has good sedimentation performance.

Simulation of Drainage System Using Storm Water Management Model (SWMM 5.1)

Abstract: Urban flood is one of the major problems in Guwahati city at present. The topography of the city is such that rainwater cannot drain out easily from the city. With rapid growth of the city, along with people cutting and constructing houses in the surrounding hills, result in high sediment yield from the immediate upper catchment, adding another dimension to this problem. The need for a proper storm water disposal drainage system is at prime in Guwahati. Therefore innovative planning and efficient design of the drainage network is necessary. An effort has been made to study finer details of the area by investigating drainage systems of various parts of the city. The existing drainage channel is studied and simulated using SWMM 5.1 modeling software. The model is simulated for rainfall of two-year return period of interval one-hour design storm intensity. Frequency analysis is performed using best fitted distribution i.e., Gumbel’s distribution for different return periods and the frequency values are used for development of IDF (intensity-duration-frequency) curves. The city is divided into major flood prone areas according to ASDMA and then modeling is done with respect to different return period of rainfall. From simulation it is found that the existing drainage of the city is not efficient to drain out the storm-water completely, the primary cause of urban flood in Guwahati city

EVALUASI SISTEM DRAINASE DALAM UPAYA PENANGGULANGAN BANJIR (STUDI KASUS KELURAHAN HONIPOPU KOTA AMBON)

Urban drainage systems serve the disposal of excess water in a city by draining it through the soil surface or passing below the ground surface, to be discharged into rivers, lakes and the sea. The excess water can be in the form of rainwater, domestic wastewater and industrial wastewater. Therefore, in order to prevent flooding in urban areas, an urban drainage system must be integrated with sanitation, garbage, city flood control and also the state of the surrounding area. The objectives of this research are 1) to identify the drainage system that always causes flooding in Honipopu Village, Ambon City; 2) Determine the direction of the right drainage system in an effort to overcome flooding in Honipopu Village, Ambon City. Data collection methods used in this study include: observation, interview techniques, agency surveys, and documentation. Analysis of the data used is an analysis of the basic physical conditions of the research area, including slope, hydrology, nalysis of the data used is an analysis of the basic physical conditions of the research area, including slope, hydrology, rainfall conditions and land use. Drainage conditions in Honipopu Village are poor due to very high sedimentation and waste water discharge causing drainage to become shallow and also to inadequate drainage system. The direction of the drainage system in an effort to cope with flooding in the Honipopu village is the rehabilitation and normalization of drainage strategies.

Extrapulmonary Tuberculosis: Clinical and Diagnostic Features and Risk Factors for Early Mortality

Objective: The aim of this study is to evaluate patients with EPTB in terms of demographics, anatomic localization, diagnosis and risk factors on early mortality. Materials and methods: The data of 217 inpatients who were followed up with EPTB, between January 2010 and December 2020, were evaluated retrospectively. Patients were followed-up during hospital admission and early mortality was considered. Risk factors on mortality were identified in multivariate analysis using logistic regression model. Results: The median age was 54 (IQR: 37-67) and the rate of male patients was 43.3%. 76 (35%) patients had at least one comorbidity. The most common underlying conditions were diabetes mellitus and immunosuppressive treatment. The most common forms of EPTB were lymph node, bone and CNS. Microbiological findings (ARB and/or TB-culture and/or M. tuberculosis PCR) were positive in 75 patients and histopathological findings (necrotising granuloma with/without pathological caseification) were supportive for diagnosis in 68.2%. The overall mortality rate was 8.5%. In the multivariate analysis, factors independently associated with increased risk of death included advanced age, elevated sedimentation rate above 50mmHg, miliary TB and CNS TB. Conclusion: In conclusion, EPTB is an important health problem in developing countries with significant mortality in specific forms. The most common forms of EPTB are lymph node, bone and CNS TB. The most common underlying conditions are diabetes and immunosuppressive therapy although most patients do not have any underlying diseases. The diagnosis is forcing and a substantial proportion of patients have negative microbiological findings. The diagnosis are based on pathological, radiological and/or clinical findings in patients without definitive microbiological diagnosis. Advanced age, high sedimentation rate and severe forms such as CNS and miliary TB are associated with early mortality.

Phenotyping for percutaneous coronary intervention and long-term recurrent weighted outcomes

IntroductionPercutaneous coronary interventions (PCI) are often performed in multimorbid patients with heterogeneous characteristics and variable clinical outcomes. We aimed to identify distinct clinical phenotypes utilizing machine learning and explore their relationship with long-term recurrent and weighted outcomes. MethodsThis prospective observational cohort study enrolled all-comer PCI patients in 2020‐2021. Multiple imputation k-means clustering was utilized to detect specific phenotypes. The study endpoints were patient-oriented and device oriented composite endpoints (POCE, DOCE), its individual components, and major bleeding. We applied semiparametric regression models for recurrent and weighted endpoints. ResultsThe study included a total of 643 patients. We unveiled three phenotype clusters: 1) inflammatory (n = 44, with high white blood cell counts, high values of C-reactive protein (CRP) and neutrophil-to-lymphocyte ratio), 2) high erythrocyte sedimentation rate (ESR) (n = 204), and 3) non-inflammatory (n = 395). For ACS-only population, we four distinct phenotypes (high-CRP, high-ESR, high aspartate-aminotransferase, and normal). For all-comer PCI patients, identified phenotypes had a higher risk of POCE (mean ratio (MR) 1.42 (95% confidence interval (CI) 1.11–1.81) and MR 2.01 (95% CI 1.58–2.56), respectively), DOCE (MR 1.61 (95% CI 1.20–2.16), MR 2.60 (95%CI 1.94–3.48), respectively), and stroke (hazard ratio (HR) 2.86 (95% CI 1.10–7.4), 6.83 (95% CI 2.01–23.2)). Similarly, high-ESR and high-CRP phenotypes of ACS patients were significantly associated with the development of clinical composite outcomes. ConclusionMachine learning unveiled three distinct phenotype clusters in patients after PCI that were linked with the risk of recurrent and weighted clinical endpoints.German Clinical Trial Registry number: DRKS00020892.

Assessment of diagnostic procedures and tools of COVID-19 among Iraqi patients: A systematic review

Background: The pandemic SARS – CoV2 is a novel virus disease that first appeared in China in December 2019. On February 24, 2020, the disease spread throughout Iraq, and many different studies were conducted on it. This study highlights the procedures for diagnosing COVID-19 and evaluating tools among Iraqi patients through a systematic review of research conducted in Iraq during the past two years (2020–2021). Methods: From March 2020 to December 31, 2021, articles on relevant themes were carefully searched in the main databases: Science Direct, PubMed, Embase, and Iraqi Academic Scientific Journals. Using keywords related to COVID-19 and Iraq yielded a total of 2743 articles. Articles were chosen for this systematic review based on inclusion and exclusion criteria, according to the PRISMA 2020 statement for reporting systematic review. Only Iraqi studies that reported data on diagnostic procedure outcomes were included, with a total of 21 articles chosen. Results: A total of 21 articles were found to be relevant, which reviewed the biochemical and hematological parameters as diagnostic procedures and tools in Iraqi patients. The biochemical parameters are as follows: triglycerides, cholesterol, APRs, liver functions tests, kidney functions tests, antibodies, cytokines, and minerals. The hematological parameters are as follows: ABO group, red blood cell (RBC) indices, white blood cell (WBC) indices, and platelet indices. Conclusion: Diagnostic procedures and tools for COVID-19 among Iraqi patients were in agreement with the majority of other global studies. High serum erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), ferritin, d-dimer, lactate dehydrogenase (LDH), and cytokines were associated with severe COVID-19 pneumonia and also hypoalbuminemia, lymphocytopenia, and neutrophilia. Biochemical and hematological parameters might be significant indicators for COVID-19 evaluation.

Assessment of heavy metal pollution in seawater, benthic flora and fauna and their ability to survive under stressors along the northern Red Sea, Egypt

The purpose of this study was to assess the north coasts of the Egyptian Red Sea, including Ras Gharieb, Hurghada, Safaga and Qusier, by evaluating the heavy metal pollution in seawater and benthic flora and fauna in the winter and summer of 2016. The concentrations of heavy metals (Fe, Mn, Zn, Cu, Ni, Cd and Pb) were analysed with an atomic absorption spectrophotometer. The results revealed that the Fe levels in the seawater ranged from 7.86 and 27.95 µg l-1, while the Zn concentrations fell between 1.83 and 5.63 µg l-1. In contrast, the recorded values of Mn, Cu, Ni, Pb and Cd in the seawater were minimal at the study sites. Regarding the biota samples, Porifera species were more adaptable than others to an accumulation of most metals in their tissues. Furthermore, seaweeds and seagrasses demonstrated remarkable adaptation in highly polluted regions, especially those with high turbidity, landfilling, sedimentation and high eutrophication rates – much more than the benthic fauna. Our research highlights the critical need for strict regulation of metal emissions in these coastal regions.

A simple approach for coffee-ring suppression yielding homogeneous drying patterns of ZnO and TiO2 nanoparticles

Evaporation-induced self-assembly in colloidal droplets is a method for organising nanoparticles on substrates, with various resulting patterns. The coffee-ring pattern is among the most common ones, but its non-uniformity limits its applicability, which led to efforts for developing coffee-ring suppression strategies. Considering the wide applicability of ZnO and TiO2 nanoparticles, there is a high demand for practical means to deposit them as uniform films. Here, we present a simple approach for obtaining highly uniform thin films of ZnO and TiO2 nanoparticles by drop-coating in ambient conditions, without using surfactants or other surface chemistry modifications. Disc-like films were obtained via a restricted evaporation achieved by covering the droplets with a lid during drying, seconded by the relatively high sedimentation rate of these nanoparticles. To better understand the assembly mechanism, the influence of suspension concentration, type and temperature of the substrate, droplet volume, colloid type, and evaporation rate were studied. The method allows preparing disc-like nanoparticle films with a good control over their diameter and thickness, onto different kinds of substrates (glass, Si, polyethylene terephthalate, polystyrene). By fabricating both two-dimensional lattices and custom disc patterns we highlight the versatility of this drop-coating method and its potential for, e.g., automatized serial production processes.

Medium-sized channel shaping in the lower Yellow River due to water–sediment regulation

Abstract The Yellow River (YR) is famous for its ‘hanging river’ due to the high sedimentation rate in the lower reaches. Reservoir sediment retention (RSR) and water–sediment regulation (WSR) of the Xiaolangdi Reservoir (XLDR) contribute to mitigating the siltation and adjusting the bankfull channel geometry in the lower Yellow River (LYR). However, few studies have been conducted to quantify the contribution of RSR and WSR to medium-sized channel shaping. In this paper, we analyzed the temporal and spatial variations of bankfull discharge (BFD) in the LYR, established empirical expressions between the BFD and the previous five-year average discharge above 2,000 m3/s and the incoming sediment coefficient during flood seasons, and then constructed three different water and sediment scenarios to quantify the contribution of the WSR of the XLDR to medium-sized channel shaping in the LYR. Calculated results indicated that WSR accounted alone for 68%–94% of the medium-sized channel shaping, with RSR contributing 6%–32%. The contribution of WSR to the recovery of medium-sized channels increased with time and became stabilized eventually. Along the LYR, such contribution also increased from 68% to 97% and eventually became stabilized in narrow reaches, reaching over 90%. The results will lay a solid technical foundation for the WSR of the XLDR, river regulation downstream of the reservoir, and sediment disposal of the YR.