scholarly journals Spatio-temporal patterns of the effects of precipitation variability and land use/cover changes on long-term changes in sediment yield in the Loess Plateau, China

2017 ◽  
Vol 21 (9) ◽  
pp. 4363-4378 ◽  
Author(s):  
Guangyao Gao ◽  
Jianjun Zhang ◽  
Yu Liu ◽  
Zheng Ning ◽  
Bojie Fu ◽  
...  
Keyword(s):  
Land Use ◽  
Surface Area ◽  
Sediment Yield ◽  
Land Surface ◽  
Sediment Load ◽  
Temporal Patterns ◽  
Precipitation Variability ◽  
Engineering Measures ◽  
Spatio Temporal ◽  
Annual Sediment

Abstract. Within China's Loess Plateau there have been concerted revegetation efforts and engineering measures since the 1950s aimed at reducing soil erosion and land degradation. As a result, annual streamflow, sediment yield, and sediment concentration have all decreased considerably. Human-induced land use/cover change (LUCC) was the dominant factor, contributing over 70 % of the sediment load reduction, whereas the contribution of precipitation was less than 30 %. In this study, we use 50-year time series data (1961–2011), showing decreasing trends in the annual sediment loads of 15 catchments, to generate spatio-temporal patterns in the effects of LUCC and precipitation variability on sediment yield. The space–time variability of sediment yield was expressed notionally as a product of two factors representing (i) the effect of precipitation and (ii) the fraction of treated land surface area. Under minimal LUCC, the square root of annual sediment yield varied linearly with precipitation, with the precipitation–sediment load relationship showing coherent spatial patterns amongst the catchments. As the LUCC increased and took effect, the changes in sediment yield pattern depended more on engineering measures and vegetation restoration campaign, and the within-year rainfall patterns (especially storm events) also played an important role. The effect of LUCC is expressed in terms of a sediment coefficient, i.e., the ratio of annual sediment yield to annual precipitation. Sediment coefficients showed a steady decrease over the study period, following a linear decreasing function of the fraction of treated land surface area. In this way, the study has brought out the separate roles of precipitation variability and LUCC in controlling spatio-temporal patterns of sediment yield at catchment scale.

scholarly journals Spatio-temporal patterns of the effects of precipitation variability and land use/cover changes on long-term changes in sediment yield in the Loess Plateau, China

2017 ◽  
Author(s):  
Guangyao Gao ◽  
Bojie Fu ◽  
Murugesu Sivapalan
Keyword(s):  
Land Use ◽  
Surface Area ◽  
Loess Plateau ◽  
Sediment Yield ◽  
Land Surface ◽  
Sediment Load ◽  
Temporal Patterns ◽  
Precipitation Variability ◽  
Spatio Temporal ◽  
Annual Sediment

Abstract. Within China's Loess Plateau there have been concerted revegetation efforts and engineering measures over the last 50 years aimed at reducing soil erosion and land degradation. As a result, annual streamflow, sediment yield and sediment concentration have all decreased considerably. Human induced land use/cover change (LUCC) was the dominant factor, contributing over 70 % of the sediment load reduction, with reductions of annual precipitation contributing the remaining 30 %. In this study, we use data on 50-year time series (1961–2011), showing decreasing trends in the annual sediment loads of fifteen catchments, to generate spatio-temporal patterns in the effects of LUCC and precipitation variability on sediment yield. The space-time variability of sediment yield was expressed as a product of two factors representing: (i) effect of precipitation (spatially variable) and (ii) fraction of treated land surface area (temporally variable). Under minimal LUCC, annual sediment yield varied linearly with precipitation, with the precipitation-sediment load relationship showing coherent spatial patterns amongst the catchments. On the other hand, the effect of LUCC is expressed in terms of a sediment coefficient, i.e., ratio of annual sediment yield to annual precipitation, which is equivalent to the slope of the sediment yield-precipitation relationship. Sediment coefficients showed a steady decrease over the study period, following a linear decreasing function of the fraction of treated land surface area. In this way, the study has brought out the separate roles of precipitation variability and LUCC in controlling spatio-temporal patterns of sediment yield at catchment scale.

Spatio-temporal analysis of the sediment yield and water turbidity at the right-bank tributaries of the Pripyat River within Ukraine

2020 ◽  
Author(s):  
Yuliia Filippova
Keyword(s):  
Sediment Yield ◽  
Sediment Load ◽  
Water Discharge ◽  
Sediment Discharge ◽  
Water Turbidity ◽  
Spatio Temporal ◽  
Annual Water ◽  
Annual Water Discharge ◽  
The Right ◽  
Annual Sediment

<p>Regularities of the river channel processes are closely related to the magnitude and variability of the river load, and the sediment yield, and the sediment yield is one of the principal factors of the riverbed formation. Cycling and dynamics of the sediment yield need to be taken into account when making hydrotechnical calculation, project work and investigating of the riverbed processes. The amount of the river loads, which find their way into the sub-basin of the Pripyat River each year, depends more on the meteorological conditions of the year. That’s why sediment yield and water turbidity are non-permanent from year to year. Since the rivers of the investigated region belong to different hydrological zones and regions, characterized by the uniqueness of water regime, which is caused by the peculiarities of hydrographic and orographic territory indexes, the content of the sediment yield and the amount are also not the same.</p><p>The water turbidity at the right-bank tributaries of the Pripyat River, which flow within the Ukrainian Polesie, is not large. The water turbidity of the Turia, Ubort River and Vyzhivka is especially small. In certain years the concentration of sediment yield can be bigger. Much more suspended particles are observed in the Styr, Sluch, and Horyn, the upper catchments of which are strongly cut and partially covered with easily washable sediments. The biggest annual average water turbidity was recorded on the Ikva River. Within the accumulative lowland in the downstream river sections, the right-bank tributaries of the Pripyat River carry cleaner water than in the upstream section since the part of sediment load of the river is build up on the riverbeds and creeks. It occurs as a result of the slope and speed reducing. However, on some right-bank rivers of Pripyat, which flow down from small local terrain uplands with cover of loamy forest and sandy sediments, water turbidity can be quite large.</p><p>The estimation of the spatio-temporal dynamics of the sediment load is accomplished by difference integral curves taking into account an average annual water discharge, maximum annual water discharge and also average annual sediment discharge and the biggest annual sediment discharge during the whole period of investigation of current hydrological posts for the right-bank tributaries of the Pripyat River within Ukraine. The analysis of synchronicity and equiphase condition of these oscillations had made it possible to identify general noticeable opposite orientation of the set of curves to the oscillation curve of general sediment load. Constructed graphs show interdependence of maximum annual water discharge, average annual sediment discharge, maximum annual sediment discharge because the sediment discharge has to react to hydraulic fluctuation in the flow.</p>

scholarly journals Using SWAT to Evaluate Streamflow and Lake Sediment Loading in the Xinjiang River Basin with Limited Data

Water ◽  
2019 ◽  
Vol 12 (1) ◽  
pp. 39 ◽  
Author(s):  
Lifeng Yuan ◽  
Kenneth J. Forshay
Keyword(s):  
Soil Erosion ◽  
River Basin ◽  
Lake Sediment ◽  
Sediment Yield ◽  
Sediment Load ◽  
Poyang Lake ◽  
Sediment Source ◽  
Sediment Loading ◽  
Source Areas ◽  
Annual Sediment

Soil erosion and lake sediment loading are primary concerns of watershed managers around the world. In the Xinjiang River Basin of China, severe soil erosion occurs primarily during monsoon periods, resulting in sediment flow into Poyang Lake and subsequently causing lake water quality deterioration. Here, we identified high-risk soil erosion areas and conditions that drive sediment yield in a watershed system with limited available data to guide localized soil erosion control measures intended to support reduced sediment load into Poyang Lake. We used the Soil and Water Assessment Tool (SWAT) model to simulate monthly and annual sediment yield based on a calibrated SWAT streamflow model, identified where sediment originated, and determined what geographic factors drove the loading within the watershed. We applied monthly and daily streamflow discharge (1985–2009) and monthly suspended sediment load data (1985–2001) to Meigang station to conduct parameter sensitivity analysis, calibration, validation, and uncertainty analysis of the model. The coefficient of determination (R2), Nash–Sutcliffe efficiency (NSE), percent bias (PBIAS), and RMSE -observation’s standard deviation ratio (RSR) values of the monthly sediment load were 0.63, 0.62, 3.8%, and 0.61 during calibration, respectively. Spatially, the annual sediment yield rate ranged from 3 ton ha−1year−1 on riparian lowlands of the Xinjiang main channel to 33 ton ha−1year−1 on mountain highlands, with a basin-wide mean of 19 ton ha−1year−1. The study showed that 99.9% of the total land area suffered soil loss (greater than 5 ton ha−1year−1). More sediment originated from the southern mountain highlands than from the northern mountain highlands of the Xinjiang river channel. These results suggest that specific land use types and geographic conditions can be identified as hotspots of sediment source with relatively scarce data; in this case, orchards, barren lands, and mountain highlands with slopes greater than 25° were the primary sediment source areas. This study developed a reliable, physically-based streamflow model and illustrates critical source areas and conditions that influence sediment yield.

scholarly journals Sediment Load and Suspended Sediment Concentration Prediction

2013 ◽  
Vol 1 (No. 1) ◽  
pp. 23-31 ◽  
Author(s):  
Bečvář Martin
Keyword(s):  
Suspended Sediment ◽  
Sediment Yield ◽  
Suspended Sediment Concentration ◽  
Sediment Load ◽  
Sediment Concentration ◽  
River Basins ◽  
River Systems ◽  
Sediment Yields ◽  
Suspended Sediment Concentrations ◽  
Annual Sediment

Sediment is a natural component of riverine environments and its presence in river systems is essential. However, in many ways and many places river systems and the landscape have been strongly affected by human activities which have destroyed naturally balanced sediment supply and sediment transport within catchments. As a consequence a number of severe environmental problems and failures have been identified, in particular the link between sediments and chemicals is crucial and has become a subject of major scientific interest. Sediment load and sediment concentration are therefore highly important variables that may play a key role in environment quality assessment and help to evaluate the extent of potential adverse impacts. This paper introduces a methodology to predict sediment loads and suspended sediment concentrations (SSC) in large European river basins. The methodology was developed within an MSc research study that was conducted in order to improve sediment modelling in the GREAT-ER point source pollution river modelling package. Currently GREAT-ER uses suspended sediment concentration of 15 mg/l for all rivers in Europe which is an obvious oversimplification. The basic principle of the methodology to predict sediment concentration is to estimate annual sediment load at the point of interest and the amount of water that transports it. The amount of transported material is then redistributed in that corresponding water volume (using the flow characteristic) which determines sediment concentrations. Across the continent, 44 river basins belonging to major European rivers were investigated. Suspended sediment concentration data were collected from various European basins in order to obtain observed sediment yields. These were then compared against the traditional empiric sediment yield estimators. Three good approaches for sediment yield prediction were introduced based on the comparison. The three approaches were applied to predict annual sediment yields which were consequently translated into suspended sediment concentrations. SSC were predicted at 47 locations widely distributed around Europe. The verification of the methodology was carried out using data from the Czech Republic. Observed SSC were compared against the predicted ones which validated the methodology for SSC prediction.

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