Suspended Sediment Sources Research Articles

Evidences of the sources of suspended sediments and ecological processes in the Yellow River Basin.

Terrestrial originated suspended sediments from the Yellow River are crucial to understand the sources of the suspended sediment and ecological processes in estuary. This study integrated physicochemical indices, stable isotopes and microbial communities to trace the origin of the suspended sediment, and investigated the importance of ecological processes in community assembly via the null model and neutral community model. Global data revealed that the dissolved and particle ratios of carbon and nitrogen obviously decreased from the headstream to the estuary. A significant positive correlation was detected between δ15N and δ13C from Henan Province to offshore. Notable differences in bacterial community composition were found between Henan Province and offshore in dry season, whereas nearly no remarkable changes were detected throughout the entire YR basin in wet season. Multiple lines of evidence from physicochemical analysis, stable isotopic and genetic tracing revealed the possibility that the terrestrially- derived suspended sediments in the lower reaches contributed the most carbon and nitrogen to the suspended sediment in the estuary. Dispersal limitations for stochastic processes had the greatest relative importance in the community assembly of the two seasons. A greater degree of homogeneous selection for deterministic processes was exhibited in dry but not wet season. Proteobacteria had a remarkable correlation with salinity and conductivity in both dry and wet seasons, while Elusimicrobiota was more strongly related to NO3-N in dry than that in wet season. Therefore, this study elucidates the source of suspended sediment in estuaries and highlights the ecological processes involved in altering the microbial community composition in Yellow River basin.

Impact of seasonal variations in fronts on suspended sediments transport off the coastal area of Fujian Province

The Zhejiang-Fujian (Zhe-Min) coastal muddy area plays a crucial role in facilitating sediment exchange through a cross-front. The mud depocenter off the Zhe-Min coastal area is a source of suspended sediment that can be transported to the continental shelf of the East China Sea (ECS). Although the front of the inner shelf of the ECS has been extensively reported, the cross-front material transport off the coastal area of Zhe-Min in summer has not been well studied, especially using measured data. To reveal how the front controls the transport of suspended sediment, this study focuses on the impact of fronts on the dispersion of suspended sediment off the coastal area of Fujian Province in different seasons. The results indicate that the front acts as a barrier, inhibiting the dispersion of suspended sediment into the sea. The high-concentration suspended sediment is mainly found to the northwest of the front, with an average SSC of 8.5 mg/L in winter and 3.1 mg/L in summer. The suspended sediment concentration (SSC) follows a V-shaped distribution along the cross-isobath transects, with lower SSC observed at the 50-m isobath compared with the shallow water area and the deep water area. The SSC at the front was the lowest, with an average concentration of 2.3 mg/L in winter and 1.9 mg/L in summer. The front is crucial for the development of the Zhe-Min coastal muddy area. The winter monsoon is strong, resulting in a sufficient supply of suspended sediments in the muddy area and a high transport flux of suspended sediments in the nearshore. The front hinders the dispersion of high-concentrated sediment from the nearshore to the offshore, resulting in the deposition of fine-grained sediments in the nearshore and the formation of an inner shelf muddy sedimentary zone. The findings of this study will help improve our understanding of the sediment source-to-sink processes in the ECS and land–sea interactions.

High-frequency spatial sediment source fingerprinting using in situ absorbance data

Sediment fingerprinting is a commonly applied approach to quantify catchment suspended sediment (SS) source contributions. However, due to the high workloads and costs involved in SS sampling and laboratory analyses, traditional procedures often result in a limited number of samples and sampling campaigns, which can hamper the capacity to capture the intra- and inter-storm variations in SS source activation and deactivation. A better understanding of the temporal dynamics in source contributions is needed, however, to improve the understanding of dynamic sediment generation and delivery processes for selecting management practices. In recognition of the extant need to improve high-frequency source estimates and to permit long duration measurement campaigns, the work reported herein presents a sediment fingerprinting procedure using UV–Vis absorbance spectra measured in situ with submersible spectrophotometer probes to estimate spatial SS source contributions based on a confluence-based monitoring strategy. The high-frequency (5-minute intervals) measurements were used to fingerprint SS sources during seven selected periods with varying hydrological conditions. Source apportionment estimates (MixSIAR model) were validated using an independent sediment budget. The results showed a mean deviation of 9.4 ± 6.0 %, compared with the sediment budget, for the seven periods combined (n = 7,282 time steps). The most accurate results (mean absolute error of 5.3 ± 4.3 %) were obtained for the period covering the July 2021 flood event in central Europe (return period for the monitored catchment > 20 years). Overall, modelled variations in SS source contributions mostly followed the sediment budget dynamics. This novel work highlights the potential for using spectrophotometer absorbance data for high-frequency and long-term sediment fingerprinting purposes. We argue that the presented method can lead to new opportunities to improve our understanding of SS sources and their dynamics.

Comparative study using spectroscopic and mineralogical fingerprinting for suspended sediment source apportionment in a river–reservoir system

AbstractThe need to control soil erosion has received increasing attention, but quantitative data on the sources of suspended sediment in many river–reservoir systems is still lacking. The goal of this research was to compare the application of spectroscopic [mid‐infrared (MIR)] and mineralogical [X‐ray diffraction (XRD)] fingerprints for assessing relative sediment source contributions from different land use groups (agricultural lands, forests and human settlements) in the Konar–Damodar river–reservoir system in India. Source apportionment was estimated using partial least square (PLS) regression for spectroscopic tracers (MIR) and the Bayesian MixSIAR model for mineralogical tracers. Both methods identified differences between the pre‐ and post‐monsoon sediment contributions of forests (overall contribution bounds of ~35–43%). During monsoon seasons, both fingerprinting methods indicated agricultural land use as the primary source of suspended sediment. Although there were some temporal variations in the predicted contributions of the land use sources, the MIR‐PLS and mineralogical–MixSIAR methods produced comparable ranges. The respective variations in contributions, using MIR‐PLS and mineralogical–MixSIAR, were ~31 to 66% compared with ~36 to 61% for agricultural lands, ~21 to 43% compared with ~15 to 39% for forests and ~16 to 37% compared with ~19 to 32% for human settlements.

Assessment of soil erosion in the Upper Citarum watershed for sustainability of the Saguling reservoir: unmixing model approach.

The Citarum watershed and the Saguling reservoir are vital natural resources in Indonesia, affecting the livelihood of West Java and the DKI Jakarta population. This study aimed to assess the soil erosion in the Upper Citarum watershed and identify its source. The study used the fallout radionuclide technique, geochemical tracers, and an unmixing model to measure soil erosion and the contribution of suspended sediment sources due to erosion. Soil bulk transects and surface soil were sampled using a coring tool on the Ciwidey and Cisangkuy sub-watersheds. Riverbank and suspended sediment samples were collected from tributaries and rivers. With 137Cs, 40% of the samples had values below the minimum detectable activity, and vice versa for 210Pbex, all samples are detectable. For mitigation, bare land needs to be recovered due to its erosion (25.6 t ha-1year-1) exceeding the tolerance erosion value (17 t ha-1year-1). Statistically, Mg and Na were the most appropriate composite tracers for suspended sediment contribution. The unmixing model predicted the sediment contributors from bare land (58%), the riverbank (32.7%), and plantation land (9.3%). Proper land conservation could reduce sediment supply by almost 14.7% and extend the reservoir's life. This is the first study to report the feasibility of the unmixing model in Indonesia.

Estimation of vertical transport timescales of sediment in the Changjiang Estuary and its adjacent regions

The concept of resuspension age was employed to assess the timescales of vertical sediment transport in the Changjiang Estuary (CJE) and its adjoining areas. Resuspension age refers to the duration elapsed since particles last made contact with the seabed. Energetic tidal current in the study area results in a significant amount of sediment being eroded into the water during spring tides, causing the resuspension age to consistently remain lower during spring tides compared to neap tides. Spatially, consistently low resuspension ages occur in the North Branch and turbidity maximum because suspended sediment in these areas primarily originates from local erosion. While advective sediment dominates in the HZB, leading to highest resuspension age there. During the wet season, the South Branch experiences an average resuspension age surpassing 10 days, primarily due to particles predominantly transported from the river. Sediments deposited on the seabed during the wet season become the primary source of suspended sediment after being eroded into the water column during the dry season, leading to a reduction in resuspension age. Likewise, the decrease in resuspension age in the Subei Coast during the dry season is closely associated with the appearance of sediment mass advected by the northern branch plume. When stratification occurs, the upward diffusion of sediment is impeded, constraining newly eroded sediment close to the bed. As a result, these sediments exhibit lower ages than those in the upper water column, where sediment transport is primarily dominated by horizontal advection.

Sources of suspended sediments in salt marsh creeks: Field measurements in China and the Netherlands

Marsh creeks are perceived as important conduits for transporting water and sediment between mudflats and marshes. In order to advance the understanding of the transport mechanisms in creeks, the source and ultimate sink of sediment which moves between mudflats and marshes through creek channels need further investigation. Therefore, two field campaigns were conducted in two intertidal systems with varying sediment availability. The water depth, flow velocity, suspended sediment concentration, and bed level change were measured simultaneously in a marsh creek and on the adjacent mudflat in Chongming Island (China) and in Paulina Saltmarsh (the Netherlands). Paulina Saltmarsh is much smaller, more frequently flooded, and has lower sediment concentration than Chongming. These contrasting conditions allow for a comparison of transport mechanisms and functioning of the creek. Both systems first show that the high suspended sediment concentration (SSC) measured in marsh creeks is mainly the consequence of sediment advection rather than local erosion. In addition, erosion in marsh creeks is usually limited during ebb tides, reducing the export of sediment through these creeks. However, differences have been observed between two systems. The measured SSC was highly asymmetric between flood and ebb tides in Chongming. Large peaks in SSC during the flood period can be observed for most tidal cycles. The marsh creeks in Chongming therefore function as conduits for sediment import. Additionally, there are distinct overbank and underbank tides in Chongming. Sediment was trapped and retained in creeks during underbank tides, which can then be eroded and transported to the marsh during subsequent overbank tides. We also observed that mudflats in Chongming quickly recovered after erosion. These mechanisms have not been observed in Paulina Saltmarsh, where net sediment export via the marsh creek was observed due to a lack of abundant sediment in suspension during flood tides. Furthermore, the remaining bed surface of mudflats after an erosion event was stronger than before, limiting further erosion in Paulina Saltmarsh. These findings from the two systems indicate that the role of creeks in sediment import/export depends on the availability of sediment from mudflats, shedding light on nourishment strategies for salt marshes.

Suspended Sediment Source and Transport Mechanisms in a Himalayan River

The process of estimating sediment load has been a daunting issue in hydraulics and the water resource field. Several methods exist for predicting the sediment load in a catchment or river, but the majority of these methods are empirical and depend on the specific location where they are used. Understanding the underlying mechanism of sediment generation and its transport in connection with precipitation, topography, and subsurface conditions to characterize its process is helpful for determining the sediment load in a river. For this purpose, we analyzed the daily suspended sediment data measured for 8 years at the headworks of the Kabeli A hydropower project in the Kabeli River, which originates from the Himalayan region. The analyses show that the suspended sediment concentration (SSC) varies in an orderly manner over time and asynchronously between seasons with respect to the river discharge. Clockwise hysteresis is observed in the yearly plots between the SSC and river discharge. The hysteresis becomes narrower when compared with the direct runoff obtained from a digital filtering algorithm and, even more so with the direct runoff from the hydrological model SWAT. The analysis shows that the sediment concentration is controlled not only by the total discharge in the river but also by the contribution of ground water to the river discharge, indicating that the total discharge alone cannot reflect the seasonal variation in SSC. It is inferred that the river is supply-limited and the hillslope is transport-limited with respect to sediment sources. The SWAT model suggests that the base flow contribution to the total river discharge is 78%. Here, we present a method for constructing the suspended sediment rating curve by comparing the direct runoff with the sediment concentration. The deduced sediment rating curve captures 84.51% of the total sediment load over the study period in the Kabeli River. This method may potentially be used in similar catchments with supply-limited rivers and transport-limited hillslopes.

13C dicarboxylic acid signatures indicate temporal shifts in catchment sediment sources in response to extreme winter rainfall

Rainfall and land-use interactions drive temporal shifts in suspended sediment sources, yet the magnitude of such changes remains poorly understood due to the lack of land-use specific source tracers. We investigated α,ω-dicarboxylic fatty acid root-specific biomarkers, as diagnostic tracers for apportioning sources of time-integrated suspended sediment samples collected from a grassland dominated agricultural catchment in the southwest of England during the wet winter period. Applying fatty acids-specific stable carbon isotope analysis and a Bayesian isotope mixing model, we show that stream banks contributed most of the sediment in the early winter, i.e. October–December, while winter cereal-dominated arable land contributed more than half of the sediment during the late winter, i.e. January–March. The dominant sediment source shifted in conjunction with a period of prolonged consecutive rainfall days in the later period suggesting that intervention required to mitigate soil erosion and sediment delivery should adapt to changing rainfall patterns. Our novel findings demonstrate that isotopic signatures of α,ω-dicarboxylic fatty acids are promising tracers for understanding the resistance of agricultural soils to water erosion and quantifying the interactive effects of extreme rainfall and land use on catchment sediment source dynamics.

Differentiating Potential Suspended Sediment Sources Using Radionuclide Tracers and Soil Organic Matter Analysis in a Headwater Catchment in Chuncheon, South Korea

Identifying potential sources of suspended sediment (SS) in headwater catchments is crucial for water quality management. To differentiate these potential SS sources, we investigated the distribution of two fallout radionuclides (FRNs), 137Cs and 210Pbex, using gamma spectrometry along with soil organic matter (SOM) analysis in a headwater catchment with five potential SS sources: cultivated land, non-harvested forest floor, eroded hillslope, harvested forest floor, and stream bank. The 137Cs and 210Pbex concentrations and the SOM content were considerably higher in the harvested forest floor materials than in the other four potential SS source materials. FRN concentrations revealed distinct properties according to the type of potential SS sources. Specifically, the combination of FRNs (with the effect of SOM content removed) associated with the mineral fraction and SOM showed distinguishable differences among the potential SS sources, except for no difference between cultivated land and eroded hillslope. Therefore, SOM and FRNs, or their combination, can be effective indices to differentiate or trace potential SS sources on various land use/land cover types within a catchment. Further field tests will allow the tracing techniques that bind FRNs with SOM to contribute to understanding SS transport from non-point sources within a catchment.

Exploring Suspended Sediment Dynamics Using a Novel Indexing Framework Based on X‐Ray Diffraction Spectral Fingerprinting

AbstractUnderstanding the origins and hotspots of suspended sediments is crucial for safeguarding the biotic communities and for management of water quality in river‐reservoir systems. This study is an attempt to develop a new analytical framework to deconvolve the suspended sediment sources contribution using a novel index (i.e., erosion susceptibility index, ESI). The ESI is computed using sediment fingerprinting information, sediment yield, and the areal coverage of the sediment sources (land use). We have used X‐ray diffraction (XRD) and Partial least square regression (PLSR) based spectral fingerprinting technique to apportion the land use classes as sources of sediments in a representative catchment of Chotanagpur Plateau (CP), India (Konar reservoir catchment). PLSR model on the XRD spectra has performed well with R2 > 0.88 and identified agricultural areas as the major contributor of suspended sediments by delivering 28%–43%, varying seasonally (in the period of 2018–2019). However, based on the ESI values barren lands and human settlements were found to be the most crucial land use classes (with highest ESI value of 1.31 and 1.08 respectively) in terms of sediment generation (22%–29% and 14%–23% respectively) with only 14% and 12% areal coverage. The results have demonstrated that the state of critical conservation urgency of different land uses can be quantified more effectively when combining spectral tracers based knowledge with ESI.

The spatio-temporal dynamics of suspended sediment sources based on a novel indexing approach combining Bayesian geochemical fingerprinting with physically-based modelling

Applications of sediment source fingerprinting continue to increase globally as the need for information to support improved management of the sediment problem persists. In our novel research, a Bayesian fingerprinting approach using MixSIAR was used with geochemical signatures, both without and with informative priors based on particle size and slope. The source estimates were compared with a newly proposed Source Sensitivity Index (SSI) and outputs from the INVEST-SDR model. MixSIAR results with informative priors indicated that agricultural and barren lands are the principal sediment sources (contributing ∼5–85% and ∼5–80% respectively during two sampling periods i.e. 2018-2019 and 2021–2022) with forests being less important. The SSI spatial maps (using % clay and slope as informative priors) showed >78% agreement with the spatial map derived using the INVEST-SDR model in terms of sub-catchment prioritization for spatial sediment source contributions. This study demonstrates the benefits of combining geochemical sediment source fingerprinting with SSI indices in larger catchments where the spatial prioritization of soil and water conservation is both challenging but warranted.

Sediment source tracing during flood events in the Huangfu River basin in the northern Loess Plateau, China

Identifying critical soil erosion areas and sediment sources are essential for sediment control and water resources management in the watershed, especially in the severely eroded northern Loess Plateau, China. In this study, we collected suspended sediment samples at the hydrological stations to identify the sediment source dynamics during flood events in a highly erodible basin, the Huangfu River basin in the Northern Loess Plateau. A total of 6 flood events were sampled during 2016 and 2018 for investigation, the flow discharge was featured by a rapid rising limb and a slow falling limb. Compared with the sediment sources, the silt fraction in the suspended sediments was enriched and the sand fraction in the suspended sediment was depleted. The dominant particle grain size of suspended sediments was coarse sand (56.89%), higher than silt (41.81%) and clay (1.3%). The sediment sources were estimated using the FingerPro unmixing model based on the conservativeness index (CI) and consensus ranking (CR) methods. The results of the unmixing model reveal that the bare land was the predominant source of suspended sediments, ranging from 40% to 57%, which was much higher than farmland (27 ∼ 31%) and grassland (16 ∼ 25%). Our findings imply that the bare land (weathered sandstone area) is the critical region for soil loss control in the Huangfu River basin. A combination of vegetation restoration measures and engineering measures are proposed to improve the sustainable development of ecological environment in the basin.

Land-use-based freshwater sediment source fingerprinting using hydrogen isotope compositions of long-chain fatty acids

Rapidly changing land use patterns and frequent extreme weather events have resulted in an increased sediment flux to freshwater systems globally, highlighting the need for land-use-based sediment source fingerprinting. Application of variability in hydrogen isotope compositions (δ2H values) of vegetation-specific biomarkers from soils and sediments is relatively underexplored for land-use-based freshwater suspended sediment (SS) source fingerprinting, but has the potential to complement the information from routinely applied carbon isotope analysis and provide new insights. We analysed δ2H values of long-chain fatty acids (LCFAs) as vegetation-specific biomarkers in source soils and SS collected from the mixed land use Tarland catchment (74 km2) in NE Scotland, to identify stream SS sources and quantify their contributions to SS. Plant growth form was the primary control on source soils LCFAs (n-C26:0, n-C28:0, n-C30:0) δ2H variability, while the isotopic composition of source water had no significant control. Forest and heather moorland soils covered with dicotyledonous and gymnosperm species were differentiated from arable land and grasslands soils covered with monocotyledonous species. SS samples collected for fourteen months from the Tarland catchment with a nested sampling approach showed monocot-based land use (cereal crops, grassland) to be the major source of SS with 71 ± 11% contribution on catchment-wide scale averaged throughout the sampling period. Storm events after a dry summer period and sustained high flow conditions in the streams during autumn and early winter suggested enhanced connectivity of more distant forest and heather moorland land uses covering relatively steep topography. This was shown by an increased contribution (44 ± 8%) on catchment-wide scale from dicot and gymnosperm-based land uses during the corresponding period. Our study demonstrated successful application of vegetation-specificity in δ2H values of LCFAs for land-use-based freshwater SS source fingerprinting in a mesoscale catchment where δ2H values of LCFAs were primarily controlled by plant growth forms.

Spatio-temporal suspended sediment fingerprinting under different land management practices

Understanding spatio-temporal suspended sediment dynamics is more important in large watersheds due to the decisive role of local source apportionment in sediment transport and yield. The Talar River with a large mountainous watershed in northern Iran, which plays a vital role in water supply for agriculture and drinking, recently has faced quality degradation. The current study explores the relative contribution of suspended sediment sources using geochemical tracers and fingerprinting techniques in high and low flow periods along this river. Soil samples were collected from four major land uses including rangeland, forest, rainfed agriculture, and irrigated agriculture, as well as riverbanks and riparian zones along the main river. Furthermore, suspended sediment was sampled at four sampling points along the main river in two seasons. Land use apportionment in suspended sediment yield was calculated using an unmixing model included in a newly developed package (FingerPro) in high flow and low flow, separately. The fingerprinting results showed a highly spatio-temporal dynamic for sediment source contribution along the main river in high and low flow periods. Natural land uses (forest and rangeland) in upstream reaches and agricultural land uses and riverbank sources in downstream reaches showed higher contributions to suspended sediment yield. The mean contribution of various land uses for both high and low flow periods indicated substantial contributions from forest (34%–41%) and riverbanks (31%–33%). The significant difference in sediment geochemical properties for the two flow seasons highlights the important role of the prevailing climatic-hydrologic condition on river sediment. Moreover, this issue indicates that sediment source contributions and transfer mechanisms are highly dynamic in Talar River watershed. The current study outcomes provide essential knowledge to create a robust strategy for mitigation of river sediment pollution.

Use of a submersible spectrophotometer probe to fingerprint spatial suspended sediment sources at catchment scale

Sediment fingerprinting is used to identify catchment sediment sources. Traditionally, it has been based on the collection and analysis of potential soil sources and target sediment. Differences between soil source properties (i.e., fingerprints) are then used to discriminate between sources, allowing the quantification of the relative source contributions to the target sediment. The traditional approach generally requires substantial resources for sampling and fingerprint analysis, when using conventional laboratory procedures. In pursuit of reducing the resources required, several new fingerprints have been tested and applied. However, despite the lower resource demands for analysis, most recently proposed fingerprints still require resource intensive sampling and laboratory analysis. Against this background, this study describes the use of UV-VIS absorbance spectra for sediment fingerprinting, which can be directly measured by submersible spectrophotometers on water samples in a rapid and non-destructive manner. To test the use of absorbance to estimate spatial source contributions to the target suspended sediment (SS), water samples were collected from a series of confluences during three sampling campaigns in which a confluence-based approach to source fingerprinting was undertaken. Water samples were measured in the laboratory and, after compensation for absorbance influenced by dissolved components and SS concentration, absorbance readings were used in combination with the MixSIAR Bayesian mixing model to quantify spatial source contributions. The contributions were compared with the sediment budget, to evaluate the potential use of absorbance for sediment fingerprinting at catchment scale. Overall deviations between the spatial source contributions using source fingerprinting and sediment budgeting were 18 % for all confluences (n = 11), for all events (n = 3). However, some confluences showed much higher deviations (up to 52 %), indicating the need for careful evaluation of the results using the spectrophotometer probe. Overall, this study shows the potential of using absorbance, directly obtained from grab water samples, for sediment fingerprinting in natural environments.

Source apportionment of suspended sediment using grain-size end-member analysis

End-members mixing analysis (EMMA) was performed on in situ suspended sediment grain-size distribution (GSD) data from Haizhou Bay to estimate suspended sediment provenance and the relative contributions of different sediment sources to total seawater suspended sediment. The results show that the suspended sediment in Haizhou Bay can be expressed as a mixture of three EMs. End-member 1 represents fine-grained suspended sediment that was transported over long distances by advection; this shows a genetic connection with the old Huanghe River delta. End-member 2 represents resuspension of local sediment, while EM3 represents riverine suspended sediment. On average, advection, resuspension, and riverine input contributed 41.92%, 37.83%, and 20.25% of the total suspended sediment, respectively. Temporal changes in advection and resuspension caused considerable variability in these relative contributions. The application of EMMA herein demonstrates that it is a feasible approach to explore suspended sediment sources and their mixing processes using suspended sediment GSD data.

Seasonal variability of Total Suspended Sediment off the Banjir Kanal Barat River, Semarang, Indonesia estimated from Sentinel-2 images

Total Suspended Sediment (TSS) is one of the important variables determining water quality since it controls the biological process in the coastal waters. TSS distribution off the Banjir Kanal Barat (BKB) River, Semarang, Indonesia previously has been investigated using remote sensing method. However, they did not use the TSS algorithm which is designated for coastal area of Semarang or they did not do proper validation process. In the present study, we generated TSS algorithm using Sentinel-2 images for the coastal waters off the BKB River based on 164 match-up data, which consists of the in-situ TSS as the truth TSS and collocated satellite measurements. With the Root Mean Square Error of 6.27 mg/L and bias of -0.29 mg/L, TSS off the BKB River can be estimated by the linear regression of red band. The seasonal variation of TSS off the BKB River is obtained by applying the linear regression equation on the cloud free Sentinel-2 images which represent each month in 2020. The maximum (minimum) TSS occur in February (May) i.e., > 150 mg/L (< 96 mg/L). High TSS plume is clearly seen off the BKB River which indicates the dominant role of BKB River as a suspended sediment source. Based on the TSS distribution criteria by Ministerial decree of environment of the Republic of Indonesia no. 54 of 2004, the coastal waters off the BKB River is categorized as polluted water. The seasonal variation of TSS follows the variation of precipitation. The high (low) precipitation causes the high (low) TSS off the BKB River. The precipitation over land may bring eroded soil that increase TSS. Thus, the management uphill land use may play an important role to control the TSS off the BKB River.

Using particle size distributions to fingerprint suspended sediment sources—Evaluation at laboratory and catchment scales

AbstractApplications of sediment source fingerprinting studies are growing globally despite the high costs and workloads associated with the analyses of conventional fingerprint properties on target sediment samples collected using traditional methods. To this end, there is a need to test new fingerprint properties that can overcome these challenges. Sediment particle size could potentially contribute here since it is relatively easy to measure but, until now, has rarely been deployed as a fingerprint itself. Instead, particle size has been used to ensure that source and target sediment samples are more directly comparable on the basis of the fingerprints used. Accordingly, this work examined whether particle size distributions (PSDs) could be used as a reliable fingerprint for apportioning sediment sources, in combination with a grain size un‐mixing model. Application of PSDs as a fingerprint was tested at two scales: (i) in a laboratory setting where soil samples with known PSDs were used to generate artificial mixtures to evaluate un‐mixing model results, and (ii) a catchment setting comparing PSDs in a confluence‐based approach to test if downstream target sediment PSDs could be un‐mixed into the contributions of sediment coming from an upstream and a tributary sampling site. Laboratory results showed that the known proportions of the two, three and four soil samples in the artificial mixtures were predicted accurately using the AnalySize grain size un‐mixing model, giving average absolute errors of 9%, 8% and 6%, respectively. Catchment results showed variable performances when comparing un‐mixing results with sediment budget estimations, with the best results obtained at higher discharge values during storm runoff events. Overall, our results suggest the potential of using PSDs for estimating contributions of sediment sources delivering SS with distinct PSDs when sources are located at short distance to the downstream sampling site.

Stream corridor and upland sources of fluvial sediment and phosphorus from a mixed urban-agricultural tributary to the Great Lakes

Like many impaired Great Lakes tributaries, Apple Creek, Wisconsin (119 km2) has Total Maximum Daily Load (TMDL) targets for reducing suspended sediment and total phosphorus by 51.2 % and 64.2 %, respectively. From August 2017 - October 2018, a stream sediment budget and fingerprinting integrated study was conducted to quantify upland and stream corridor sources of suspended sediment and sediment-bound phosphorus. Phosphorus concentrations varied among source groups and fluvial sediments, with higher concentrations among suspended sediment and cropland soils. Eroding streambanks identified in the stream corridor sediment budget accounted for 100 % of the TMDL Soil and Water Assessment Tool (SWAT) suspended sediment load but only 20 % of the total phosphorus load. Fine-grained streambed sediment equated to approximately-three years of modeled suspended sediment load but only one third of total phosphorus load. The two primary sources of fine-grained streambed sediment were streambanks and cropland, with relative streambank contributions increasing with downstream direction and watershed area. The relative proportion of suspended sediment varied by season and streamflow; however, cropland and streambank erosion accounted for 54 % and 23 % of the suspended sediment when weighted by of the proportion for representative streamflow. Urban land was a source in the upper watershed, but the signature was sequestered by a mid-watershed detention basin. Contributions from construction sites were higher in the fall 2018, likely corresponding to increased activity following a wet spring. These integrated techniques helped describe sources, transport, and sinks of fluvial sediment and phosphorus throughout the watershed at a range of spatial and temporal scales.