Branch Channel Research Articles

Laboratory Flume and Numerical Modeling Experiments Show Log Jams and Branching Channels Increase Hyporheic Exchange

AbstractLog jams alter gradients in hydraulic head, increase the area available for hyporheic exchange by creating backwater areas, and lead to the formation of multiple channel branches and bars that drive additional exchange. Here, we numerically simulated stream‐groundwater interactions for two constructed flume systems—one without jams and one with a series of three jams—to quantify the effects of interacting jam structures and channel branches on hyporheic exchange at three stream flow rates. In simulations without jams, average hyporheic exchange rates ranged from 2.1 × 10−4 to 2.9 × 10−4 m/s for various stream discharge scenarios, but with jams, exchange rates increased to a range of 1.3 × 10−3–3.5 × 10−3 m/s. Largely due to these increased hyporheic exchange rates, jams increased stream‐groundwater connectivity or decreased the turnover length that stream water travels before interacting with the hyporheic zone, by an order of magnitude, and drove long flow paths that connected multiple jams and channel threads. Decreased turnover lengths corresponded with greater reaction significance per km, a measure of the potential for the hyporheic zone to influence stream water chemistry. For low‐flow conditions, log jams increased reaction significance per km five‐fold, from 0.07 to 0.35. Jams with larger volumes led to longer hyporheic residence times and path lengths that exhibited multiple scales of exchange. Additionally, the longest flow paths connecting multiple jams occurred in the reach with multiple channel branches. These findings suggest that large gains in hydrologic connectivity can be achieved by promoting in‐stream wood accumulation and the natural formation of both jams and branching channels.

Insight into the dynamics of non-Newtonian carboxy methyl cellulose conveying CuO nanoparticles: significance of channel branch angle and pressure drop

Abstract Branching channels are commonly emerged in a considerable variety of engineering applications, in which most of the fluids present non Newtonian behavior, such as in chemical processes. It is noted that in the material forming process, when one suspends nanoparticles in a basic non Newtonian fluid, a completely new non Newtonian fluid is formed with different rheological characteristics from the former ones. In our present numerical research, considering the side branches inclined at varying angles, we focus on the fluid flow and heat transfer of the laminar power-law nanofluid in a rectangular branching channel under the influences of generalized Reynolds number. Both the consistency coefficient and power-law index of the non Newtonian nanofluid, different from those of the base fluid, are described by empirical formula, dependent on the nanoparticle quantity. Finite element method is applied in the research. It is found that a smaller branch angle α can cause a larger fluctuation in pressure near the branched region. Furthermore, negative pressures exist both in the main and side branch with some certain inclination angle. Above all, the new extensive results of velocity contours, temperature, concentration contours along with pressure drop of the changing rheological models provide detailed information for studies on non Newtonian nanofluids in many intricate industrial applications.

Influences of wall superheat and channel width ratio on bubble behaviors and heat transfer within a heated microchannel T-junction

Despite many studies conducted to reveal the bubble behaviors and associated heat transfer within straight microchannels, those within heated microchannel T-junctions are relatively few. In this paper, the ANSYS Fluent 17.0 enhanced by user-defined functions (UDFs) is utilized to perform 2D simulations on an evaporating bubble passing through the heated T-junction. The influences of wall superheat (ΔT) and channel width ratio (W*) are investigated. Four typical breakup regimes (Non-breakup, “Tunnel” breakup type one, “Tunnel” breakup type two, and obstructed breakup) are observed and the corresponding phase diagram is drawn. The heat transfer characteristics for different heated walls are quantitatively assessed. The bubble behaviors have great impact on the heat transfer characteristics of T-junction. The oscillation of relatively small bubble produces obvious local heat transfer enhancement. The occurrence of tunnel is found to weaken the heat transfer enhancement. It should be noted that the serpentine flow structure occurring at larger W* also significantly influences the heat transfer of branching channel. Generally, the overall heat transfer performance tends to increase with increasing ΔT or decreasing W*. This study contributes to a better understanding of bubble behaviors within microchannel T-junctions.

Formation and capture of droplet with high volume ratio of cell to droplet

High volume ratio of cell to droplet is of great importance for the fast detection on the secreted molecule by rapidly increasing the concentration of the molecule to the detectable level. In this paper, small-volume satellite droplet that encapsulates the cell is continuously generated and captured by a T-shaped microchannel with a branching channel to achieve high volume ratio of cell to droplet. The influence of the flow rate of the continuous phase, the channel geometry and the cell concentration on the formation of the satellite droplet is systematically studied by the experiment. The results show that the smallest satellite droplet with size of ∼6.5 μm (∼0.14 pl in volume) can be generated at a low cell concentration of 16.7% and an average volume ratio of cell to droplet can be achieved as high as ∼45.9% (the relative standard deviation is 12.9%). With advantages of continuous manipulation and high volume ratio of cell to droplet, the present method could be potentially utilized as a prerequisite step for the fast detection on the secreted molecule.

Tetraselmis jejuensis sp. nov. (Chlorodendrophyceae), a Euryhaline Microalga Found in Supralittoral Tide Pools at Jeju Island, Korea.

We found the euryhaline microalga, Tetraselmis jejuensis sp. nov., which was adapted to supralittoral tide pools with salinities varying from 0.3–3.1%. Fifteen strains of T. jejuensis were isolated from Daejeong (DJ) and Yongduam (YO), and clonal cultures were established in the laboratory. Morphological characterization revealed that the cells have a compressed shape, four flagella emerging from a depression near the apex in two opposite pairs, a cup-shaped chloroplast containing one pyrenoid surrounded by starch, and eyespot regions not located near the flagellar base. T. jejuensis cells showed distinct characteristics compared to other Tetraselmis species. First, a regular subunit pattern with honeycomb-like structures was predominantly displayed on the surface in the middle of the cell body. Second, the pyrenoid was invaded by both cytoplasmic channels comprising electron-dense material separated from the cytoplasm, and two branches of small cytoplasmic channels (canaliculi) in various directions, which characterize the subgenus Tetrathele. Eyespot regions containing a large number of osmiophilic globules, packed closely together and arranged in subcircular close packing of diverse sizes, were dispersed throughout the chloroplast. In the phylogenetic analysis of small subunit (SSU) rDNA sequences, the 15 strains isolated from DJ and YO separated a newly branched clade in the Chlorodendrophyceae at the base of a clade comprising the T. carteriiformi/subcordiformis clade, T. chuii/suecica clade, and T. striata/convolutae clade. The strains in the diverging clade were considered to belong to the same species. The SSU rDNA sequences of the DJ and YO strains showed a maximum difference of 1.53% and 1.19% compared to Tetraselmis suecica (MK541745), the closest species of the family based on the phylogenetic analysis, respectively. Based on morphological, molecular, and physiological features, we suggest a new species in the genus Tetraselmis named Tetraselmis jejuensis, with the species name “jejuensis” referring to the collection site, Jeju Island, Korea.

COMBINED ELECTROOSMOTIC AND PRESSURE DRIVEN FLOW IN TREE-LIKE MICROCHANNEL NETWORK

The present work presents a simplified mathematical model to calculate the flowrate of the combined electroosmotic flow (EOF) and pressure driven laminar flow (PDLF) in the symmetric tree-like microchannel network under the assumptions of small zeta potential and thin electrical double layer. A numerical analysis of the combined EOF and PDLF in symmetric Y-shaped microchannel is also carried out to validate the mathematical model. The analytical results and numerical results are found to be in good agreement with each other. Using the mathematical model, the present work further investigates the effect of diameter ratio of the tree-like network on the flowrate of the combined EOF and PDLF to recognize a possible conclusion being similar to the Murray’s law. Based on the present work, it is found that the symmetric tree-like network has an optimal diameter ratio to achieve the maximum flowrate for the combined EOF and PDLF when the total microchannel volume is constant; however, this optimal diameter ratio for the combined flow disobeys the generalized Murray’s law in a simple form of power function of the branching number [Formula: see text], and it is not only related on the branching number, but also depends on the branching level and channel length ratio of the tree-like network. Furthermore, the optimal diameter ratio shows a monotonous transition from [Formula: see text] for the pure PDLF to [Formula: see text] for the pure EOF with the increasing ratio of the driven voltage and driven pressure. The present work discusses the effects of these parameters on the optimal diameter ratio for the combined EOF and PDLF.

Efficient Generation of Microdroplets Using Tail Breakup Induced with Multi-Branch Channels.

In recent years, research on the application of microdroplets in the fields of biotechnology and chemistry has made remarkable progress, but the technology for the stable generation of single-micrometer-scale microdroplets has not yet been established. In this paper, we developed an efficient and stable single-micrometer-scale droplet generation device based on the fragmentation of droplet tails, called “tail thread mode”, that appears under moderate flow conditions. This method can efficiently encapsulate microbeads that mimic cells and chemical products in passively generated single-micrometer-scale microdroplets. The device has a simple 2D structure; a T-junction is used for droplet generation; and in the downstream, multi-branch channels are designed for droplet deformation into the tail. Several 1–2 µm droplets were successfully produced by the tail’s fragmentation; this continuous splitting was induced by the branch channels. We examined a wide range of experimental conditions and found the optimal flow rate condition can be reduced to one-tenth compared to the conventional tip-streaming method. A mold was fabricated by simple soft lithography, and a polydimethylsiloxane (PDMS) device was fabricated using the mold. Based on the 15 patterns of experimental conditions and the results, the key factors for the generation of microdroplets in this device were examined. In the most efficient condition, 61.1% of the total droplets generated were smaller than 2 μm.

One-dimensional channel network modelling and simulation of flow conditions during the 2008 ice breakup in the Mackenzie Delta, Canada

This paper presents recent developments to River1D's (the University of Alberta's public-domain hydrodynamic and river ice process model) channel network modelling capabilities. While previous versions of the model assumed equal water surface elevations through the junction, the approach presented in this paper takes into account the significant physical effects at channel junctions (such as gravity and flow separation forces, and channel resistance). The adapted approach is also equipped with the ability to dynamically change junction configurations (i.e. diverging to converging or vice versa) as the result of flow reversals. The intent here was to develop an approach that would permit the simulation of flow in a channel network that includes the more important physical effects at junctions but without the need to adjust model parameters or redefine junctions should a flow reversal occur. This momentum based approach to simulate junctions is assessed using a series of steady and unsteady tests using a 2D model, the University of Alberta's River2D, for comparison. For the diverging junction tests, the proposed 1D network model performed very well with respect to the discharge split. The model accurately simulated the water surface elevation in the two receiving channels but tended to overestimate the water surface elevation immediately upstream of the junction, perhaps attributable to model discretization and/or neglecting the centrifugal forces acting on the main channel as the lateral channel branches off. For the two parallel channels with a perpendicular connecting channel tests, the 1D model agreed well with the 2D model for all steady and unsteady tests. The unsteady test results demonstrated how capable the 1D model is at handling transient flow reversals. The model is then applied to a network of channels in the Mackenzie Delta. The model was calibrated and validated for three open water events, and subsequently used to simulate flow conditions during the 2008 breakup. Model results agreed well with observed water level data collected using data loggers. A comparison of the model flows for the pre-jam and ice-jam conditions suggests that ice jamming can significantly impact the distribution of flow in the upper Mackenzie Delta. For the ice-jam conditions, the simulated flow reversal in the Peel Mackenzie Connector is consistent with observations in this channel during the 2008 breakup.

Dependence of tides and river water transport in an estuarine network on river discharge, tidal forcing, geometry and sea level rise

Estuaries are often characterised by a complex network of branching channels, in which the water motion is primarily driven by tides and fresh water discharge. For both scientific reasons and management purposes, it is important to gain more fundamental knowledge about the hydrodynamics in such networks, as well as their implications for turbidity and ecological functioning. A generic 2DV estuarine network model is developed to study tides and river water transport and to understand the dependence of their along-channel and vertical structure on forcings, geometry characteristics and sea level changes. The model is subsequently applied to the Yangtze Estuary to investigate tides and the distribution of river water over channels during dry and wet season, spring tide, as well as prior to and after the formation of Hengsha Passage and the construction of the Deep Waterway Project and sea level rise. Increasing river discharge enhances the friction for tides by increasing both internal and bottom stresses. Changes in tidal forcing are correlated with the friction for both tide and river. A shortcut channel reduces the water level difference in adjacent channels, as well as tidal amplitudes difference. Sea level rise results in larger friction parameters and faster propagation of tides. The distribution of river water transport is hardly affected by above mentioned changes. Model results and current vertical structure are consistent with observations.

Using the Submerged vanes to control the sediment entering branch channel with 30° angle with the direction of the main channel

Using the Submerged vanes to control the sediment entering branch channel with 30° angle with the direction of the main channel

Data assimilation of flow-acoustic resonance.

A data assimilation (DA) strategy was developed for accurate prediction of the flow-acoustic resonant fields within a channel-branch system. The challenges of numerical simulation of such internal aeroacoustic systems are primarily associated with determination of the transfer loss between the acoustic waves and the shear layer vortices. Thus, a data-assimilated momentum loss model that comprises a viscous loss item and an inertial loss item was established and embedded into the Navier-Stokes equations. During the DA, the acoustic pressure pulsations measured from a dynamic pressure array served as the observational data, the ensemble Kalman filter served as the optimization algorithm, and a three-dimensional transient computational fluid dynamics method comprising an explicit algebraic Reynolds stress model (EARSM) served as the predictive model system. EARSM was used because its ability to predict internal flow-acoustic resonances was superior to that of other eddy viscosity models and Reynolds stress models. The data-assimilated flow-acoustic resonant fields were then comprehensively validated in terms of their acoustic fields, time-averaged flow fields, and phase-dependent flow fields. The time-averaged flow fields were obtained from planar particle-image velocimetry (PIV) measurements, and the phase-dependent flow fields were obtained from field programmable gate array-based phase-locking PIV measurements. The results demonstrate that the use of DA afforded an optimal simulation that efficiently decreased the numerical errors in the frequencies and amplitudes of the acoustic pressure pulsations, thereby achieving better agreement between time-averaged flow distributions and fluctuations. In addition, the data-assimilated numerical simulation completely reproduced the spatiotemporal evolution of the shear layer vortices, that is, their formation, developing, transport, and collapsing regions.

Alternate Route Selection of Self-Propelled Filter Papers Impregnated with Camphor for Two-Branched Water Channels.

The route selection of self-propelled filter papers impregnated with camphor for two-branched water channels was investigated. The two-branched water channel was composed of a stem channel and two branch channels, and the branch channels were connected to the stem channel at a junction. When a single camphor paper reached the junction from the stem channel, it selected one of the two routes equivalently. Three or five camphor papers which were placed on a stem channel exhibited either alternate or random route selection depending on the characteristic length between the leading and following papers, Lc. That is, the alternate route selection of the camphor papers for the two-branched water channels was observed at Lc ≤ 25 mm. By contrast, the alternate route selection was broken at Lc > 25 mm. The physicochemical meaning of the threshold value, Lth ∼ 26 mm, between the alternate and random route selections was discussed based on the experimental results. In addition, the distribution length of camphor molecules developed from the leading camphor paper and the change in the spatial gradient of surface tension around the junction supports the value of Lth. These results suggest that autonomous phenomena using inanimate self-propelled objects are important to understand collective motion in living organisms.

The Lithological Features of Sublacustrine Fans and Significance to Hydrocarbon Exploration: A Case Study of the Chang 7 Interval of the Yanchang Formation, Southeastern Ordos Basin, North China

The Chang 7 interval of the Upper Triassic Yanchang Formation in the Ordos Basin represents a typical deep lacustrine depositional sequence. On the basis of field outcrops, cores, well logs, light/heavy mineral provenance analysis, and petrological studies, we evaluated the characteristics of deep-water gravity flow deposition of the Chang 7 interval and constructed a depositional model. The sediments mainly came from the northeast of the study area, and multiple sublacustrine fans were deposited in the center of the basin. Different from the deep-marine fan, the sublacustrine fan in the study area develops under the background of gentle slope without any erosional canyon between the fan and delta front. Gravity flow deposits in the study area can categorised into three groups: sand debris flow deposits, turbidity current deposits, and deep-water mudstone deposits. The main channel and branch channel are mainly developed with thick massive sandy debris sandstone, while the channel lateral margin and branch channel lateral margin are mainly developed with middle massive sandy debris sandstones and turbidite sandstones, which from bottom to top, the thickness of sand layer becomes thinner and the grain size becomes smaller. Thin mudstone is developed between channels; the lobe fringe includes sheet-like turbidite sandstones and deep lake mudstones. The widely distribute, good quality source rocks ( TOC = 2 % – 6 % ) developed in deep lacustrine have attained the peak stage of oil generation ( R o = 0.9 % – 1.2 % ). The superimposition of the sublacustrine fan sand bodies and the wide distribution of good quality source rocks favor the formation of large lithologic reservoirs characterized by source–reservoir integration, self-generation and self-storage, and near-source accumulation.

Analysis of temperature uniformity of electric vehicle battery system with swirling flow strengthened heat transfer

Abstract In this paper, a novel battery thermal management (BTM) model based on swirling flow was established to ensure the safety of new energy vehicle. The computational fluid dynamics (CFD) method were utilized to investigate the effects of the number of branch channel (n) and diameter ratio (C) of cold plate. The maximum surface temperature would be reduced by increasing the number of channel, and at the same time, the pressure drop also was increased. The results showed that the maximum surface temperatures of the battery pack were decreased by 5.7%, 1.3%, 1.4%, 3.8%, and 6.5% with Reynolds numbers of 126, 252, 378, 504 and 630, respectively, by applying the branch channel with C = 0.25. The temperature standard deviations of the cold plate was declined by 20.7%, 13.7%, 11.1%, 11.7%, and 13.5% as well. Furthermore, the performance evaluation criterion (PEC) with different number of branch pipes was analyzed. When the Reynolds numbers were 126, 252, 378, 504 and 630 with n = 2, PECs were 4.66, 5.08, 5.14, 5.18, and 5.20, respectively. Based on the analysis of Nusselt number and flow resistance coefficient of channel, the BTM could achieve the most efficiency when n was 2.

Devising a model of the airflow with dust particles in the intake system of a vehicle’s internal combustion engine

This paper considers the mechanism of malfunction of internal combustion engines that implies the accelerated local wear of parts in individual cylinders as a result of uneven distribution of dust particles that pass through the air filter in the intake system. In order to acquire quantitative data on the effect of the structure of the intake system on the redistribution of dust in engine cylinders, the two-phase flow of air with dust particles in the standard elements of the intake system was mathematically modeled. ANSYS software package was used to solve the problem. A simulation technique was devised in which the airflow was first calculated to determine the boundary conditions for dust, after which the flow of air with particles was calculated. The calculations were carried out in a range of air velocities of 5‒20 m/s in branching channels with diversion angles of 45°, 90°, and 135° for the most characteristic particle sizes of 5‒30 µm. It has been estimated that dust particles deviate from the air streamlines by inertia and can slip through the lateral drain the stronger the larger particle size, diversion angle, and velocity of air. The comparison of the simulation results with experimental data confirmed that in the intake system of some engines, due to uneven particle distribution, there is local abrasive wear in one or more cylinders, which can significantly reduce the resource. This paper shows the need to take into consideration the centrifugation and redistribution of dust in the intake systems during the design, modernization, expert studies to determine the causes of faults associated with faulty operating conditions, as well as to clarify the regulations for the maintenance of existing engines.

Fabrication of microvascular constructs using high resolution electrohydrodynamic inkjet printing

Fabrication of the intricate anatomy of vasculature within engineered tissue remains one of the key challenges facing the field of tissue engineering. We report the use of electrohydrodynamic (EHD) inkjet printing to create hydrogel-based microvascular tissues with hierarchical and branching channels, whose minimum feature size of 30 μm approaches the physical scale of native capillary blood vessels. The principle relies on the use of complementary thermoreversible gelling properties of Pluronic F127 (PF-127) and gelatin methacryloyl, which served as sacrificial templates and permanent matrices respectively. Human dermal fibroblasts and human umbilical vein endothelial cells were successfully co-cultured within the engineered microvascular tissue constructs for up to 21 days, and attained high cell viability. Tissue specific morphology was maintained on perfusion. The ability to create cellularised, vascularised proto-tissues with high spatial resolution using EHD inkjet printing, provides a new strategy for developing advanced vascular models with the potential to impact upon an extensive range of biomedical applications.

Thermoelectric generation in bifurcating channels and efficient modeling by using hybrid CFD and artificial neural networks

Thermoelectric power generation within TEG mounted branching channels is considered with finite element method. In the heat transfer fluid of bifurcating channels, nanodiamond + Fe3O4 binary particles are used for further system performance improvement. It was observed that when compared to non-bifurcating channels, TEG power will be reduced with the use of branching channels while branching location also affects the interface temperature variations. At (Re1, Re2)=(1000, 200), TEG power is reduced 34.7% when both channels are branching while it is 9.9% for only upper channel branching case as compared to non-branching channel case. Up to 18% variation of power is obtained when location of the upper branching channel varies. Highest powers are achieved when both channels are filled with hybrid nanofluid while at (Re1,Re2)=(1000,200) TEG power rises by about 33% and 15.5% with nanofluid in both channels and with nanofluid in only one channel cases when compared to fluid in both channel configuration. The computational cost of electric potential and power generation in TEG device is drastically reduced from 6 hours with fully coupled high fidelity CFD to 3 minutes by using hybrid CFD and artificial neural networks. The proposed approach will very helpful in the efficient design and optimization of TEG installed renewable energy systems.

Effect of Main Channel Bed Roughness on the Branch Channel Discharge . (C)

In light of the current complex water situation in Egypt, scientists and researchers have to develop alternative plans to provide new quantities of water by paying attention to the constructions and tools that are used in distributing and controlling the flow in open channels. One of the most critical parameters in the analysis of diversion channel flow is the discharge ratio (Qr). It is the primary goal of this research to investigate the effect of changing the bed roughness of the main channel on the discharge of the branch channel (Qb). The bed roughness of the branch channel was kept constant (nb = 0.01), while for the main channel bed roughness was changed to five values (nm = 0.01, 0.016, 0.023, 0.033, and 0.04). The diversion angle of the branch channel was taken as (45˚), which gave a maximum (Qr) as recommended by some researchers. A discharge range from 4.88 to 17.14 L/sec was used, and 35 runs were conducted. From the analysis of the laboratory data, it was found that the discharge ratio (Qr) decreases as the total discharge through the main channel increases. While it increases with the increase of bed roughness ratios (nr). Moreover, at the bed roughness ratios (nr) ranged from 2.20 to 3.0, the difference in the discharge ratio (Qr) is no significant, for all discharge values passing through the main channel. Thus, maintaining a constant flow rate for the branched channel is considered one of the most essential factors in designing these channels, as it is vital in distributing water shares as percentages and in a consistent manner.

Depositional architecture, evolution and controlling factors of the Miocene submarine canyon system in the Pearl River Mouth Basin, northern South China Sea

Submarine canyon system in the Miocene Pearl River Mouth Basin, northern continental margin of the South China Sea, records the process of sediments transported from shelf margin to advanced abyssal plain and comprises important petroleum reservoirs in the basin. Based on integrated analysis of seismic, well logs and core data, the sequence framework, depositional architecture and controlling factors of the submarine canyon system are well documented. As a composite sequence bounded by regional unconformity, the Zhujiang Formation (CS1) can be divided into 5 sequences (CS1-1-CS1-5), and the lower CS1-2 and CS1-3 are the main strata that the submarine canyon system developed. The submarine canyon system can be divided into five segments (A-E) by their distinct geomorphology and depositional architectures. From Segment A to E, the channels in the submarine canyon system transform from “V” shaped single channel, “U” shaped single channel, “gull-wing” shaped channel-levee complex, “W” shaped branch channels to mound shaped distal composite channel and front splay deposits. This is accordantly consistent with sedimentary process of the channels transitional from erosional, erosional-aggradational, aggradational and then lateral migrational. The changing interaction of multi-source sediment supply, differential tectonic subsidence and relative sea level change are considered to be the major control on the development and evolution of the submarine canyon system. The differential tectonic subsidence since the Late Oligocene produced the adequate slope angle, sufficient accommodation and distinct basin geomorphology for the development and segmentation of the submarine canyon system. Slope-gully to slope fan deposits fed by the shelf margin delta systems from the Paleo-Pearl River and the northeastern Dongsha Uplift converged into the submarine canyon system, providing abundant sediments for its development. Relative sea level changes, especially the two regional regressions with abundant sediment supply have made great influence on the evolution of the submarine canyon system.

Case Study: Influence of Three Gorges Reservoir Impoundment on Hydrological Regime of the Acipenser sinensis Spawning Ground, Yangtze River, China

After the construction of the Three Gorges Dam (TGD) in China, the downstream has been affected by the reduction in sediment discharge and regulation of flow processes, which have resulted in severe scouring and changes hydrological regime. Consequently, the spawning ground of Chinese sturgeon distributed along the downstream Yichang reach could be affected. This study examined the effects of TGD on the streamflow, sediment load and channel morphology downstream based on in situ measured data. Results showed that, after the impoundment of the TGD, sediment load at the downstream Yichang hydrological station decreased significantly, and the Yichang reach continued to be scoured. The distribution of erosion was uneven, and the scouring mainly occurred in the branching channels. The channel gradient and riverbed roughness increased with the erosion of the river cross section. After more than 10 years of erosion, the riverbed scouring and armouring in the Yichang reach was basically completed, thus we expected that the spawning grounds of Chinese sturgeon could be retain as the riverbed tends to be stable. The findings in this work have implications in the protection of the critically endangered Chinese sturgeon.