Suspended Sediment Particles Research Articles

Determination of the particle load based on detailed suspended sediment measurements at a hydropower plant

Suspended sediment particles contained in inflows of water systems of hydropower plants (HPPs) cause hydro-abrasive erosion of the hydraulic turbines and structures leading to significant maintenance costs, efficiency reductions, and downtime. Relevant parameters such as suspended sediment concentration (SSC), particle size distribution (PSD), shape, and mineralogical composition were measured with an online multi-frequency acoustic instrument and based on manually taken samples from the end of the sand trap of the Toss HPP in the Himalayan region, India. In the laboratory, the samples were analyzed using the gravimetric method, laser diffraction, turbidity, dynamic digital image processing, scanning electron microscope, petrography analysis, energy-dispersive X-ray spectroscopy, and X-ray diffraction. The online instrument and the samples provided measurement results at a single point. To investigate vertical gradients in concentration and particle sizes, additional samples were collected 9 times at 7 relative water depths. The SSC, most particle sizes, and particle shape were found to be evenly distributed over depth except d90, i.e. the diameter which is not exceeded by 90% of the particle mass. d90 measured at 76% of the water depth was in the range of fine sand and was multiplied by 1.05 to obtain an average value representative for the entire depth. Improved methodologies to quantify both particle shape and size in an analytical model for hydro-abrasive erosion are proposed. Also, the PSD measuring performance of laser diffraction and dynamic imaging was studied and similar values of the median particle sizes were obtained from both instruments. Further, multi-frequency acoustic, turbidity and laser diffraction techniques were found suitable for SSC measurement at the test case HPP.

Modeling stratified suspension concentration distribution in turbulent flow using fractional advection–diffusion equation

The distribution of suspended sediment particles in a steady, uniform and stratified turbulent flow through open-channels is investigated in this study using fractional advection–diffusion equation (FADE). Unlike previous studies on FADE, the FADE is employed with the effects of stratification due to the presence of the sediment particles. Analogous to the approach of stratified flow, the effect of stratification is connected with the damping of the sediment diffusivity. A general model of sediment diffusion coefficient in stratified flow is proposed which changes along vertical direction as well as with the order of the fractional derivative. Finally the model of sediment distribution is derived incorporating the effects of non-local transport of particles, stratification, hindered settling velocity and damping of mixing length. The model is solved numerically using the fractional Adams–Bashforth–Moulton method and solutions are validated with the experimental data. The validation results are satisfactory. The variation of the depth average sediment diffusion coefficient and the proposed model of sediment diffusion coefficient with the fractional order $$\alpha$$ are investigated. The results show that with the decrease of fractional order $$\alpha$$, the value of depth average sediment diffusion coefficient increases and the depth variable sediment diffusion coefficient shows a overall increases throughout the flow depth. The rationality of the dependence of $$\alpha$$ on both types of sediment diffusion coefficients have been justified physically. It is also found that the effect of stratification results a decrease both for the suspension distribution and the sediment diffusion coefficient which is consistent with the results using traditional ADE.

Evaluation of a simple, inexpensive, in situ sampler for measuring time‐weighted average concentrations of suspended sediment in rivers and streams

AbstractThe accurate measurement of suspended sediment (<200 μm) in aquatic environments is essential to understand and effectively manage changes to sediment, nutrient, and contaminant concentrations on both temporal and spatial scales. Commonly used sampling techniques for suspended sediment either lack the ability to accurately measure sediment concentration (e.g., passive sediment samplers) or are too expensive to deploy in sufficient number to provide landscape‐scale information (e.g., automated discrete samplers). Here, we evaluate a time‐integrated suspended sediment sampling technique, the pumped active suspended sediment (PASS) sampler, which collects a sample that can be used for the accurate measurement of time‐weighted average (TWA) suspended sediment concentration and sediment particle size distribution. The sampler was evaluated against an established passive time‐integrated suspended sediment sampling technique (i.e., Phillips sampler) and the standard discrete sampling method (i.e., manual discrete sampling). The PASS sampler collected a sample representative of TWA suspended sediment concentration and particle size distribution of a control sediment under laboratory conditions. Field application of the PASS sampler showed that it collected a representative TWA suspended sediment concentration and particle size distribution during high flow events in an urban stream. The particle size distribution of sediment collected by the PASS and Phillips samplers were comparable and the TWA suspended sediment concentration of the samples collected using the PASS and discrete sampling techniques agreed well, differing by only 4% and 6% for two different high flow events. We should note that the current configuration of the PASS sampler does not provide a flow‐weighted measurement and, therefore, is not suitable for the determination of sediment loads. The PASS sampler is a simple, inexpensive, and robust in situ sampling technique for the accurate measurement of TWA suspended sediment concentration and particle size distribution.

Economic explicit-implicit schemes for solving multidimensional diffusion-convection problems

This work concerns the development of an efficient parallel algorithm for numerical solution of nonstationary diffusion-convection problems by means of a multiprocessor computer system with distributed memory. Economically explicit-implicit difference schemes and the method of splitting into physical processes are used as a basis. The original problem is replaced by a sequence of one-dimensional and two-dimensional difference problems using complex schemes that approximate the original problem in the general sense. Explicit-implicit difference schemes involve explicit approximation in horizontal directions and implicit approximation with weights in a vertical direction and require less time for solving diffusion-convection problems compared to explicit schemes while maintaining acceptable accuracy of solutions. The algorithm is proposed to find the optimal weight value and it yields the lowest approximation error in the solution of the diffusion-convection problem in the vertical direction for given time grid steps. The three-dimensional model problem of transport of suspensions in the water environment is considered. The model takes into account the following processes: advective transport caused by the movement of the water medium, microturbulent diffusion and gravitational deposition of suspended particles, as well as changes in the geometry of the bottom caused by the deposition of suspended particles or the rise of sediment particles. Application of the parallel algorithm developed for numerical modeling of suspension transport makes it possible to significantly improve the real-time forecast accuracy and the validity of the accepted engineering decisions used in designing the objects of coastal infrastructure.

HYDRODYNAMIC MECHANISM OF TURBIDITY CURRENTS IN ESTUARY STRATIFICATIONS

Water stratification commonly exists in nature, such as thermocline in lakes and oceans and halocline in estuaries and oceans (He et al. 2017). Turbidity currents in estuary often encounter stratified sea water, which may significantly influence their propagation and deposition. This study presents high-resolution numerical simulations of lock-exchange gravity and turbidity currents in linear stratifications on a flat bed. Laboratory experiments are conducted to validate the numerical model and good agreements between numerical results and measurements are found. The evolution process, front velocity, internal wave, and entrainment ratio are analyzed based on the numerical results. For a gravity current in a strong stratification, its front velocity can be maintained as a near constant state for a long time after an initial acceleration period because of interactions between the current and internal waves. However, sedimentation of suspended particles due to the damping effect of ambient stratification on turbulence makes a turbidity current quickly lose its structure so the maintaining effect of the internal waves on its front velocity is quite weak. During the evolution process of a turbidity current, the ambient stratification is found to damp the turbulent structures, and front velocity. Stratification can also decrease the entrainment ratios between a gravity current and ambient water after the initial period, but it has an insignificant influence on the entrainment ratios of a turbidity current. This study provides a better understanding of gravity and turbidity currents in estuary stratifications.

Development and correctness analysis of the mathematical model of transport and suspension sedimentation depending on bottom relief variation

Introduction. The paper is devoted to the study on the three-dimensional model of transport and suspension sedimentation in the coastal area due to changes in the bottom relief. The model considers the following processes: advective transfer caused by the aquatic medium motion, micro-turbulent diffusion, and gravity sedimentation of suspended particles, as well as the bottom geometry variation caused by the particle settling or bottom sediment rising. The work objective was to conduct an analytical study of the correctness of the initial-boundary value problem corresponding to the constructed model.Materials and Methods. The change in the bottom relief aids in solution to the initial-boundary value problem for a parabolic equation with the lowest derivatives in a domain whose geometry depends on the desired function of the solution, which in general leads to a nonlinear formulation of the problem. The model is linearized on the time grid due to the “freezing” of the bottom relief within a single step in time and the subsequent recalculation of the bottom surface function on the basis of the changed function of the suspension concentration, as well as a possible change in the velocity vector of the aquatic medium.Research Results. For the linearized problem, a quadratic functional is constructed, and the uniqueness of the solution to the corresponding initial boundary value problem is proved within the limits of an unspecified time step. On the basis of the quadratic functional transformation, we obtain a prior estimate of the solution norm in the functional space L2 as a function of the integral time estimates of the right side, and the initial condition. Thus, the stability of the solution to the initial problem from the change of the initial and boundary conditions, the right-hand side function, is established.Discussion and Conclusions. The model can be of value for predicting the spread of contaminants and changes in the bottom topography, both under an anthropogenic impact and due to the natural processes in the coastal area.

Electrophoretic deposition studies of Ba(Zr‐Ce‐Y)O3 ceramic coating

AbstractElectrophoretic deposition (EPD) is now a well established colloidal processing technique which uses electrophoresis mechanism for the movement of suspended charged particles in a suspension in the presence of an electric field. In this work, electrophoretic deposition of BaZr0.4Ce0.4Y0.2O3‐δ (BZCY) in ethanol medium was performed under different conditions on both conducting and non‐conducting (porous anode) substrate without using any external additives in a suspension bath. Process parameters such as deposition time, voltage, and rate of deposition of suspended particles were studied under various conditions. Green coating deposited under different potential (30, 50, and 70V) was uniform and crack free, even at extended time of deposition. Surface roughnesses have also been evaluated to correlate it with deposition conditions. It is also found that the rate of deposition on conducting substrate was higher as compared to that on non‐conducting substrate (anode). XRD studies of the calcined powder and coating exhibit an expected simple cubic perovskite structure. The deposition yield increases linearly with voltage for each deposition time for both conducting and non‐conducting substrates. The coating on non‐conducting porous anode heat treated at 1500°C for 2 hours was dense and well adherent to the anode substrate. A film thickness of about 13 μm was obtained at 70V. Such dense BZCY electrolyte coating on BZCY+NiO anode (Half cell) could be well utilized for fabrication of proton conducting SOFC single cell by applying suitable cathode layer on electrolyte film.

Influence of live microbes on suspended sediment concentration in coastal ecosystem

Microbes present in both fresh and saline water associate with suspended sediments by secrete extracellular polymeric substance to survive under stressful environmental conditions. Deposition of these bio-contaminated sediments affects the bed ecosystem. When re-suspended, they further affect water quality and health of both human as well as aquatic life. In this study, laboratory experiments are conducted in an annular flume to understand the interaction between suspended sediments attached with microbes (biosediment) and without microbes (non-biosediment) at different mix ratios (Mr = 0:1, 0.25:0.75, 0.50:0.50, and 1:0) and water salinity (S = 0, 1, 2, 5, 10, and 35 g/L). Results show that, rate of deposition increases with an increase in biosediment concentration for any water salinity and mix ratio. In saline water, presence of microbes on suspended sediments induces more deposition until water salinity of 5 g/L and thereafter deposition reduces. Presence of 25% and 50% of biosediment in water increases deposition up to a critical salinity of 1.72 g/L and 2.60 g/L, respectively. Suspended sediment particle size increases with an increase in biosediment concentration and decreases with an increase in water salinity. Fractal dimension results show that, when salinity increases, fragile non-biosediment and dense biosediments are retained in suspension. This study shows that presence of live microbes on suspended sediments affects their depositional behaviour.

Flow class analyses of suspended sediment concentration and particle size in a mixed-land-use watershed

Knowledge gaps remain concerning fundamental suspended sediment physical processes/relationships, such as particle size class dynamics and hydroclimatic variability. Streamwater grab samples were collected four times per week (Oct. 2009–Feb. 2014) at nested-scale gauging sites (n = 5), representing contrasting dominant land use practices. Streamflow was monitored in situ. Grab samples were analyzed for total suspended sediment concentration and mean particle size using laser particle diffraction. Comparisons were performed of suspended sediment parameters corresponding to different streamflow classes (i.e. 20th, 40th, 60th, 80th, and 99th percentile flows). Average suspended sediment concentrations displayed a decreasing trend from the predominately agricultural headwaters to the urbanized mid-watershed, and a subsequent increase to the suburban lower watershed. Results indicated significant (p < 0.05) differences in concentrations corresponding to different flow classes, with concentrations at more urban sites displaying greater “sensitivity” to streamflow variability. Significant (p < 0.05) differences between concentrations at different sites were found, but concentrations became progressively more similar (p > 0.05) at higher flows. Mean particle size results displayed significant differences (p < 0.05) between flow classes at every site. Notably, results showed a decrease in particle size during progressively higher flows, despite expectations based on stream velocity/competence relationships. Significant (p < 0.05) spatial differences in particle size were found between sites, specifically for flows within the 20th and 40th percentile flow class. However, the spatial pattern was weakened at higher flows (60th, 80th, and 99th percentile flow classes) as sites displayed greater statistical similarity. Collectively, results highlight the compounding influences of streamflow variability and land use practices on suspended sediment regimes; and considering unexpected results regarding relationships between particle size and flow, emphasize the need for continued research concerning particle size dynamics.

Particle bound pollutants in rivers: Results from suspended sediment sampling in Globaqua River Basins

Transport of hydrophobic pollutants in rivers such as polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and heavy metals is often facilitated by suspended sediment particles, which are typically mobilized during high discharge events. Suspended sediments thus represent a means of transport for particle related pollutants within river reaches and may represent a suitable proxy for average pollutant concentrations estimation in a river reach or catchment. In this study, multiple high discharge/turbidity events were sampled at high temporal resolution in the Globaqua River Basins Sava (Slovenia, Serbia), Adige (Italy), and Evrotas (Greece) and analysed for persistent organic pollutants such as PAHs (polycyclic aromatic hydrocarbons) or PCBs (polychlorinated biphenyls) and heavy metals. For comparison, river bed sediment samples were analysed as well. Further, results are compared to previous studies in contrasting catchments in Germany, Iran, Spain, and beyond. Overall results show that loadings of suspended sediments with pollutants are catchment-specific and relatively stable over time at a given location. For PAHs, loadings on suspended particles mainly correlate to urban pressures (potentially diluted by sediment mass fluxes) in the rivers, whereas metal concentrations mainly display a geogenic origin. By cross-comparison with known urban pressure/sediment yield relationships (e.g. for PAHs) or soil background values (for metals) anthropogenic impact – e.g. caused by industrial activities – may be identified. Sampling of suspended sediments gives much more reliable results compared to sediment grab samples which typically show a more heterogeneous contaminant distribution. Based on mean annual suspended sediment concentrations and distribution coefficients of pollutants the fraction of particle facilitated transport versus dissolved fluxes can be calculated.

Properties of sediments deposited in a fluid with different pH

The effect of pH on the physical and mechanical properties of a sediment was investigated through a set of experimental tests. The sediment was formed from deposition of suspended particles in a fluid. Two different types of clay soil were suspended in fluids with different pH (2, 4, 7, 9 and 11) in cylindrical tubes with volume of 1 liter and also in special cylindrical reservoirs. The height of the sediment was measured in the cylindrical tube until equilibrium was achieved. The sediment deposited in the reservoirs was dried in air and then Atterberg limit, compaction and unconfined compressive strength (UCS) tests were conducted on samples prepared from each sediment. The results showed that the final height of the settled sediment is a function of pH; the height of sediment is increased with increasing the pH. Also, the Atterberg limits increased with increasing the pH. The maximum dry unit weight and optimum water content decreased and increased with increasing the pH. The final strength of the sediment decreased with increasing pH. Based on the SEM analysis, it was found that the values of pH influence the properties of the formed sediments.

Deposition regularity in a rainwater pipeline based on variable transport flux

Experiments of the deposition of suspended particles in a rainwater pipeline were combined with mathematical model fitting to explore deposition regularity under variable transport flux. The simulation results showed that four primary factors affected deposition regularity in a rainwater pipeline. In particular, the deposition and flushing processes alternately dominated when the flow and initial suspended solids (SS) concentration changed simultaneously. The migration of the easy deposition position (EDP, the position with the largest deposition velocity) displayed an obvious regularity, shifting from front to back along the pipe regularly at increasing flow, and from back to front when flow decreased.

Purification Effect of Submerged Macrophyte System with Different Plants Combinations and C/N Ratios

A submerged macrophyte pond can effectively remove nitrogen and phosphorus from water, with the removal efficiencies for pollutants depending on combinations of submerged macrophytes. Moreover, the material structure of sewage also has a significant impact on the purification effect of the submerged macrophyte system. This experiment selected three submerged plants (Vallisneris spiralis, Hydrilla verticillata, and Myriophyllum spicatum) to examine the purification effect of their combinations on sewage, including nitrogen and phosphorus removal efficiencies. In addition, the effect of influent C/N ratio on the submerged macrophyte pond was also tested and discussed. The results showed the following. ① All plant combinations can decrease concentrations of nitrogen and phosphorus in water, resulting from nutrient deposition along with sedimentation of suspended particles. The combinations of Vallisneris spiralis and Hydrilla verticillata showed the highest purification efficiency for total nitrogen and total phosphorus with an average removal rate of 32.71% and 22.13%, respectively. ② The purification effects of three C/N ratio (1.89, 5.93, and 12.09) for Vallisneris spiralis and Hydrilla verticillate system were different. The removal efficiency was highest when the C/N ratio was 5.93, with removal rates for total nitrogen and total phosphorus and a reduction in permanganate index of 81.34%, 68.26%, and 88.65%, respectively. The C/N ratio affected the degradation of nitrogen, phosphorus, and organic matter by influencing the dissolved oxygen concentration of water and changing the anaerobic and aerobic environment of the water. In conclusion, different submerged macrophyte combinations showed better purification effect than a single type of plant in the submerged plant pond system. Changing the influent C/N ratio by placing carbon source materials into the water can greatly increase the removal efficiency of submerged plant pond, providing a practical reference for the use of submerged plant ponds to treat sewage.

Influence of suspended sediment characteristics on the bioaccumulation and biological effects of citalopram in Daphnia magna

The influence of suspended sediment (SPS) characteristics on the bioavailability of the antidepressant citalopram (CIT) was investigated in the cladoceran Daphnia magna. The bioaccumulation, swimming behaviours, psychological indices, and oxidative stress were examined. The CIT bioaccumulation were altered in the presence of SPS, such that the body burden of CIT decreased as the concentration of SPS increased and as the organic carbon content of SPS (foc) increased; moreover, the body burden of CIT increased as SPS particle size increased. All the biomarker activities of D. magna were markedly induced at a CIT exposure concentration of 10 μg/L. However, the biological effects of CIT did not depend on the body burden of CIT as SPS concentration increased, while the swimming activities and oxidative stress were significantly enhanced by SPS concentration at 1 g/L. The influences of SPS particle size and foc on the activities of swimming and physiological indicators were mainly associated with the CIT bioaccumulation, while foc in SPS was more substantial than particle size. In addition, the antioxidant activities decreased as foc increased and were significantly strengthened at particle sizes of 30–60 μm. The impacts of different SPS characteristics on the adsorption and desorption capacity of CIT and the ingestion habits of D. magna were the main reasons for the variations in CIT body burden and biological effects. According to the results obtained in this study, the SPS characteristics should be considered in the risk assessment of contaminants in natural aquatic environments.

A systematic approach to evaluate the influence of environmental conditions on eDNA detection success in aquatic ecosystems.

The use of environmental DNA (eDNA) to determine the presence and distribution of aquatic organisms has become an important tool to monitor and investigate freshwater communities. The successful application of this method in the field, however, is dependent on the effectiveness of positive DNA verification, which is influenced by site-specific environmental parameters. Factors affecting eDNA concentrations in aquatic ecosystems include flow conditions, and the presence of substances that possess DNA-binding properties or inhibitory effects. In this study we investigated the influence of different environmental parameters on the detection success of eDNA using the invasive goby Neogobius melanostomus. In a standardized laboratory setup, different conditions of flow, sediment-properties, and fish density were compared, as well as different potential natural inhibitors such as algae, humic substances, and suspended sediment particles. The presence of sediment was mainly responsible for lower eDNA detection in the water samples, regardless of flow-through or standing water conditions and a delayed release of eDNA was detected in the presence of sediment. Humic substances had the highest inhibitory effect on eDNA detection followed by algae and siliceous sediment particles. The results of our study highlight that a successful application of eDNA methods in field surveys strongly depends on site-specific conditions, such as water flow conditions, sediment composition, and suspended particles. All these factors should be carefully considered when sampling, analyzing, and interpreting eDNA detection results.

SedFoam-2.0: a 3-D two-phase flow numerical model for sediment transport

Abstract. In this paper, a three-dimensional two-phase flow solver, SedFoam-2.0, is presented for sediment transport applications. The solver is extended from twoPhaseEulerFoam available in the 2.1.0 release of the open-source CFD (computational fluid dynamics) toolbox OpenFOAM. In this approach the sediment phase is modeled as a continuum, and constitutive laws have to be prescribed for the sediment stresses. In the proposed solver, two different intergranular stress models are implemented: the kinetic theory of granular flows and the dense granular flow rheology μ(I). For the fluid stress, laminar or turbulent flow regimes can be simulated and three different turbulence models are available for sediment transport: a simple mixing length model (one-dimensional configuration only), a k − ε, and a k − ω model. The numerical implementation is demonstrated on four test cases: sedimentation of suspended particles, laminar bed load, sheet flow, and scour at an apron. These test cases illustrate the capabilities of SedFoam-2.0 to deal with complex turbulent sediment transport problems with different combinations of intergranular stress and turbulence models.

An Experimental Setup with Radial Injection for Investigation of Transport and Deposition of Suspended Particles in Porous Media

Abstract A radial injection experimental setup is presented in this paper, which allows one to study the transport and deposition of suspended particles and permeability impairment in porous media. This setup allows one to simulate the conditions of the injection of produced water in oil reservoirs from an injection well. This is achieved by a radial injection of water containing suspended particles of a few microns in size from a central well including a sand screen, through a confined cylindrical sand pack (diameter 52 cm, height 40 cm). A peripheral drainage system permits the recovery of the fluid at the outlet of the sand pack by a collector equipped with a turbidimeter for measuring the concentration of suspended particles. The injection pressure is measured at the inlet, and six pore pressure probes have been installed at different locations inside the sand pack. First experimental results presented show a significant heterogeneity of deposited particle profiles in both radial and axial directions.

WITHDRAWN: A transient model for nozzle clogging – Part II: Validation and verification

Abstract Part I of this two-part work discusses a transient two-way coupling model for clogging of nozzle (fluid passage) due to deposition of suspended particles on the nozzle wall. The purpose of Part II is to validate and verify the model. To this end, the current model simulates a laboratory experiment, designed to study the clogging of a submerged entry nozzle (SEN) during steel continuous casting. It demonstrates that the model can reproduce the experiment satisfactorily: the numerically-calculated clogged section of the nozzle is qualitatively comparable with typically “as-clogged” sections in laboratory experiments; the calculated mass flow rate through the nozzle during clogging process as function of time is also in agreement with the experimentally-monitored result. The simulation-experiment agreement depends on parameters, e.g. mesh size, Lagrangian time scale, correction factor in interpolation of clog permeability, and porosity in the clog materials, which act as inputs for the numerical model. Uncertainties for choosing such parameters, model capabilities/limitations due to model assumptions have been studied and discussed in this paper. In this regard, further model refinements are suggested. The modeling results provide new knowledge about clogging behavior. (1) Clogging is a transient process, and it includes the initial coverage of the nozzle wall with deposited particles, the evolution of a bulged clog front, and then the development of branched structure. This transient growth of clog interacts with the flow. (2) Clogging is a stochastic and self-accelerating process.

Spatiotemporal variability of suspended sediment particle size in a mixed-land-use watershed

Given existing knowledge gaps, there is a need for research that quantitatively characterizes spatiotemporal variation of suspended sediment particle size distribution (PSD) in contemporary watersheds. A five-year study was conducted in a representative watershed of the central United States utilizing a nested-scale experimental watershed study design, comprising five gauging sites partitioning the catchment into five sub-watersheds. Streamwater grab samples were collected four times per week, at each gauging site, for the duration of the study period (Oct. 2009–Feb. 2014). Samples were analyzed using laser particle diffraction. Significantly different (p<0.05) suspended sediment PSDs were observed at monitoring sites throughout the course of the study. For example, results indicated greater proportions of silt at site #5 (65%), relative to other sites (41, 32, 29, and 43%, for sites #1–#4, respectively). Likewise, results showed greater proportions of sand at sites #2 and #3 (66 and 68%, respectively), relative to other sites (57, 55, and 34%, for sites #1, #4, and #5, respectively). PSD spatial variability was not fully explained by hydroclimate or sub-watershed land use/land cover characteristics. Rather, results were strengthened by consideration of surficial geology (e.g. supply-controlled spatial variation of particle size). PSD displayed consistent seasonality during the study, characterized by peaks in the proportion of sand (and aggregates) during the winter (i.e. 70–90%), and minimums during the summer (i.e. 12–38%); and peaks in the proportion of silt particles in the summer (i.e. 61–88%) and minimums in the winter (i.e. 10–23%). Likely explanations of results include seasonal streamflow differences. Results comprise distinct observations of spatiotemporal variation of PSD, thereby improving understanding of lotic suspended sediment regimes and advancing future management practices in mixed-land-use watersheds.

Dynamics of suspended sediment concentration, flow discharge and sediment particle size interdependency to identify sediment source

Spatiotemporal behavior of sediment yield is a key for proper watershed management. This study analyzed statistical characteristics and trends of suspended sediment concentration (SCS), flow discharge (FD) and sediment particle sizes using data from 24 gage stations scattered throughout the United States. Analysis showed significant time- and location-specific differences of these variables. The median values of SSC, FD and percentage of particle sizes smaller than 63µm (P63) for all 24 gage stations were found to be 510.236mgl−1 (right skewed), 45.406m3s−1 (left skewed) and 78.648% (right skewed), respectively. Most of the stations exhibited significant trends (P<0.001) in daily SSC (18 stations; one increasing and 17 decreasing), FD (19 stations; seven increasing and 12 decreasing), and P63 (15 stations; five increasing and 10 decreasing) as well. Further, 46% of the stations exhibited significant trends in all three variables. The wash load significantly contributed (79.085±11.343%) to sediment load recorded at the gage stations. Results of the study can be used for developing best watershed management practices which may call for local or regional planning based on natural (i.e., precipitation amount, type and erosivity, watershed area, and soil erodibility) and human-affected (i.e., land use and hydraulic structures and water resources management) factors governing the study variables.