Quantifying the temporal variation of the contribution of fine sediment sources to sediment yields from Chilean forested catchments during harvesting operations
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Abstract:
Fingerprinting techniques were incorporated into a paired catchment investigation in southern Chile to quantify the contribution of three fine sediment sources (catchment surfaces, forest roads and stream channels) to catchment suspended sediment yields during forest harvesting and replanting operations. Optimum composite fingerprints for use in sediment source discrimination and apportionment comprised 137Cs and 210Pbex for the control catchment (LUC) throughout the study and for the treatment catchment (LUT) during the pre-harvest period, and 137Cs and soil organic matter during harvest and post-harvest periods for LUT. Prior to harvesting, the dominant sediment source to the sediment load in both catchments was the stream channel and remained relatively constant throughout the study for LUC. For the entire study period the total suspended sediment yield from LUT (3,160 kg ha-1) approximately doubled that from LUC (1,650 kg ha-1). Most of this difference is accounted for by the increase in sediment output during the rainy months following clearcutting. The disturbance associated with forest operations in LUT caused the contributions to the load from the catchment slopes and forest roads to increase markedly (total contributions 835 and 795 kg ha-1, respectively). However, the total contribution from the stream channel for LUT during the study period (1,530 kg ha-1) remained similar to that from LUC. The results of the investigation demonstrated that any attempt to reduce sediment loading from forest harvesting would require adopting best management practices to reduce sediment mobilization from catchment surfaces and forest roads.Keywords:
Variation (astronomy)
Sedimentary budget
This study disclosed the variation of sediment fluxes through the worldwide second largest sediment routing system by constructing the sediment budget of the system over the period from 1855 to 1968. The results show that the overall incoming sediment over that period was 1878×10 8t,and 62% and 32% of the incoming sediment deposited in the lower Yellow River and in the delta respectively. It was also shown that the percentage of sediment deposited in the lower Yellow River changed with the construction of dykes,the promotion of flood prevention capacity of dykes, dam construction,and use of water and sediment in recent periods. Over the period from 1855 to 1968 the total mass of sediment deposited on the delta was 609×10 8t, accounting for 84% of the sediment carried down to the river mouth. The effect of time scale on the estimated proportion of sediment deposited on the delta was found to be noticeable.
Sedimentary budget
River delta
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Abstract Measurements of sediment transport have been undertaken on many rivers throughout the world. Most of the available data relate to suspended sediment loads and the results provide a wealth of information on the variation of suspended sediment yields in both space and time. This contribution reviews current knowledge regarding land–ocean sediment transfer and sediment fluxes to the oceans, global patterns of sediment yield and their controls, and temporal variability of sediment yields in response to both natural controls and human activity and environmental change. In order to understand the sediment response of a drainage basin, it is important to take account of the complex linkages between sediment mobilisation and sediment output, and particularly the role of both short‐ and long‐term storage. The sediment budget provides a useful conceptual framework for this purpose and current understanding of the structure of catchment sediment budgets is reviewed.
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Using methods combining statistical data analysis with practice discussion,the flow/sediment data of Lijin hydrological station and the influencing mechanism of Xiaolangdi on flow/sediment variation were analyzed.The results show that: Flow/sediment regulation of Xiaolangdi changes the annual distribution,the beginning phase of flood season advancing to June and the ending phase extending to November,the difference between flood season and non-flood season are getting smaller,the annual distribution of flow/sediment are tending to uniform,but in general,the annual flow/sediment are less 27.4%,72.1%,when compared with that in natural conditions;by adjusting the flow/sediment allocation,the ratio of flow/sediment and incoming sediment coefficient tend to normalize and rationalize(0.01 t/m3,0.01 kg·s/m6),and the flow/sediment combination is improved obviously,which is very significant for maintaining the dynamic balance of the estuary sand spit mouth and coastal in Yellow River Delta(YRD);Xiaolangdi project makes the YRD maintain a certain flow and flood peak(3 000~4 000 m3/s) all the year-round,which restrains effectively the occurrence of flow-break,moreover,sediment composition remarkably coarsens.
Sedimentary budget
River delta
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AbstractThis study investigates the sediment fluxes through the Yellow River sediment routing system, which are among the largest in the world, by constructing a sediment budget of the system over the period from 1855 to 1968. The framework of the sediment budget includes four functional units with the upper and middle reaches of the river as the sediment source and its lower reaches, its delta, and the deep sea as the sediment sinks. Sediment yield from the source and amounts of deposition in the lower Yellow River and the modern Yellow River delta were estimated for completing the sediment budget. The sediment budget produced for the period from 1855 to 1968 was characterized by a sediment input of 1.837 × 1011 tonnes and a distribution of the sediment between the lower Yellow River, the delta, and the deep sea of 64%, 33%, and 3%, respectively. The details of the sediment budget show that the importance of sedimentation in the lower Yellow River changed greatly with variations in the condition of the dykes and other human activities. A comparison of the sediment budgets of the delta for different timescales shows that the proportion of sediment dispersed to the deep sea decreases as the timescale over which the sediment fluxes are investigated increases.Key words: Yellow Riversediment routing systemsediment budgethuman impacts
Sedimentary budget
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Rocky intertidal systems are useful to study the influence of measurement scale on spatial biological variation in community structure. Vertical biological variation across elevations (triggered by tides) has typically been found higher than horizontal (alongshore) variation at local scales but lower than horizontal variation at regional scales. In those studies, alongshore environmental variation increased with scale. We surveyed the Canadian and Chilean coasts at those scales but with a limited underlying alongshore environmental variation and found that horizontal biological variation was never higher than vertical biological variation. Predicting spatial scales of biological variation should thus consider the underlying environmental variation. These photographs illustrate the article “Interhemispheric comparison of scale-dependent spatial variation in the structure of intertidal rocky-shore communities” by Alexis M. Catalán, Nelson Valdivia, and Ricardo A. Scrosati published in Ecosphere. https://doi.org/10.1002/ecs2.3068.
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Intertidal ecology
Temporal scales
Geographic variation
Rocky shore
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There have been abundant research results on sediment variation in the middle reaches of the Yellow river. The current research results have been summarized from three facts: changes of the sediment variation with time and space, some questions in the research on the sediment variation and trend prediction of the future sediment variation. Based on the existing results, some views for the research on the sediment variation there have been put forward.
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Sedimentary budget
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The method of soil erosion monitoring assisted by sediment budget is proposed.It is analyzed that the coupling relationship between the soil erosion monitoring and the three parts of sediment budget includes the sediment source,sediment storage and sediment yields.The methods of soil erosion monitoring using sediment budget and its feasibility in different spatial-temporal condition are analyzed.
Sedimentary budget
WEPP
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Reliable estimates of sediment-budget errors are important for interpreting sediment-budget results. Sediment-budget errors are commonly considered equal to sediment-budget imbalances, which may underestimate actual sediment-budget errors if they include compensating positive and negative errors. We modified the sediment ‘fingerprinting’ approach to qualitatively evaluate compensating errors in an annual (1991) fine (<63 μm) sediment budget for the North Halawa Valley, a mountainous, forested drainage basin on the island of Oahu, Hawaii, during construction of a major highway. We measured concentrations of aeolian quartz and 137Cs in sediment sources and fluvial sediments, and combined concentrations of these aerosols with the sediment budget to construct aerosol budgets. Aerosol concentrations were independent of the sediment budget, hence aerosol budgets were less likely than sediment budgets to include compensating errors. Differences between sediment-budget and aerosol-budget imbalances therefore provide a measure of compensating errors in the sediment budget. The sediment-budget imbalance equalled 25 per cent of the fluvial fine-sediment load. Aerosol-budget imbalances were equal to 19 per cent of the fluvial 137Cs load and 34 per cent of the fluvial quartz load. The reasonably close agreement between sediment- and aerosol-budget imbalances indicates that compensating errors in the sediment budget were not large and that the sediment-budget imbalance is a reliable measure of sediment-budget error. We attribute at least one-third of the 1991 fluvial fine-sediment load to highway construction. Continued monitoring indicated that highway construction produced 90 per cent of the fluvial fine-sediment load during 1992. Erosion of channel margins and attrition of coarse particles provided most of the fine sediment produced by natural processes. Hillslope processes contributed relatively minor amounts of sediment. © 1998 John Wiley & Sons, Ltd.
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Abstract This article aims to provide a broad overview of the topic across spatial scales ranging from small catchments to a global perspective. The two elements of the topic (i.e. sediment yields and sediment budgets) are closely related, with the former treating the catchment or river basin essentially as a black box. The latter looks into the black box to consider the importance of sediment sources, and sediment mobilization, transport, and storage in influencing sediment yields. Attention is directed firstly to the key features of sediment yields, by considering fluvial sediment loads, measurement techniques, the magnitude of sediment yields, and associated global and regional patterns and key controlling factors. Information on spatial variability of sediment yields is complemented by consideration of medium‐ and longer‐term temporal variability in response to natural factors and, more importantly, the impact of anthropogenic activity and climate change. Sediment budgets are introduced by considering the important role of internal storage in influencing the sediment yield from a catchment or river basin and the concepts of the sediment delivery ratio and connectivity, as well the need to take account of the sediment sources involved. Examples of sediment budgets are provided and available techniques for assembling the information necessary to establish a sediment budget are reviewed.
Sedimentary budget
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Based on analyzing natural environment characteristics of different producing runoff and producing sediment regions in the Yellow River basin,principles and indexes of determining more sediment and coarse sediment region have been mainly discussed and area of more sediment and coarse sediment region is calculated.It is to research coupling relations among different producing runoff and sediment regions in the Yellow River basin and runoff and sediment in the middle reaches of the Yellow River.Ratio that producing runoff volume and sediment delivery occupy total runoff and sediment in the four stations(Huaxian,Zhuangtou,Longmen and Hejin)are calculated,they are that producing annual runoff volume and sediment delivery occupy total runoff and sediment in four stations of the Yellow River 12.9% and 63.4% respectively,in which 87% of coarse sediment in the four stations comes from the more sediment and coarse sediment region.Controlling more sediment and coarse sediment region is a key for reducing sediment of four stations.It is estimated that controlling 10 000 km 2 more sediment and coarse sediment region can reduce 8% of total sediment and 10% coarse sediment respectively.
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