scholarly journals Multidecadal Sediment Balance Modelling of a Cascade of Alpine Reservoirs and Perspectives Based on Climate Warming

Water ◽  
2018 ◽  
Vol 10 (12) ◽  
pp. 1759 ◽  
Author(s):  
Sebastián Guillén-Ludeña ◽  
Pedro Manso ◽  
Anton Schleiss
Keyword(s):  
Climate Warming ◽  
Sedimentation Rate ◽  
Sediment Yield ◽  
Swiss Alps ◽  
Active Management ◽  
Data Series ◽  
Sediment Fluxes ◽  
Sediment Balance ◽  
Total Sedimentation ◽  
Annual Sediment

This paper presents a comprehensive methodology to model and determine the annual sediment balance of a complex system of interconnected reservoirs, based on the detailed interpretation of a multi-decadal data series of reservoir management and modelling of sediment fluxes. This methodology is applied to the reservoirs of Oberaar, Grimsel, Räterichsboden, and Trift, which are located in the Swiss Alps. Additionally, the effects of climate warming on the annual sediment yield are investigated. Modelling results show that at present, the hydropower cascade formed by Oberaar, Grimsel, and Räterichsboden retains about 92% of the annual sediment yield, of which only the finest fraction leaves the system and enters the river network. Very fine sediments (d < 10 μm) account for 28% of the total sedimentation rate and in the case of Oberaar, it can reach up to 46% of the total sedimentation rate. Under a climate warming scenario, both sediment yield and runoff are expected to increase in terms of the annual average throughout the XXIst century, which will likely lead to greater annual inputs of sediments to the reservoirs. This, in turn, will lead to a higher sedimentation rate and suspended sediment concentration in the reservoirs, unless active management of the sediment fluxes is implemented.

scholarly journals Sediment balance of a cascade of alpine reservoirs based on multi-decadal data records

2018 ◽  
Vol 40 ◽  
pp. 03012
Author(s):  
Sebastián Guillén Ludeña ◽  
Pedro Manso ◽  
Anton J. Schleiss ◽  
Benno Schwegler ◽  
Jan Stamm ◽  
...  
Keyword(s):  
Sedimentation Rate ◽  
Reservoir Sedimentation ◽  
Sediment Fluxes ◽  
Fine Sediments ◽  
Sediment Balance ◽  
Operational Management ◽  
Human Use ◽  
Bottom Outlets ◽  
Total Sedimentation ◽  
Annual Sediment

Reservoir sedimentation is a major concern in the operational management of dams and appurtenant structures. The increasing volume of sediments deposited in reservoirs leads to a loss of water storage, undermining the purpose itself of the dam for human use or protection. The deposition of sediments (mostly fine) in the vicinity of the dam’s operational structures, such as bottom outlets and power intakes, may result in partial or total blockage of these structures. To cope with these problems, it is essential to determine the sediment balance of the reservoirs, by assessing the origin and quantity of the in- and out-fluxes of sediments. This paper presents a methodology to determine the annual sediment balance of a system of interlinked reservoirs across several decades, as well as its application to the alpine hydropower cascade formed by the Oberaar, Grimsel and Räterichsboden reservoirs located in Switzerland. At that aim, the annual sediment fluxes and the sedimentation rates of each reservoir were characterized. Also, the percentage of fine sediments (dm < 10 μm) included in the total sedimentation rate was estimated. The results reveal that the annual sedimentation rate of the lowermost reservoir of the system (Räterichsboden) is highly altered by the flushing operations of the reservoir upstream (Grimsel). Also, for the uppermost reservoir of the system (Oberaar), the volume of fine sediments deposited annually can reach up to 46% of the total sedimentation rate.

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 Climate change impacts the protective effect of forests: A case study in Switzerland

2021 ◽  
Author(s):  
Christine Moos ◽  
Antoine Guisan ◽  
Christophe F. Randin ◽  
Heike Lischke
Keyword(s):  
Climate Change ◽  
Protective Effect ◽  
Climate Warming ◽  
Swiss Alps ◽  
Present Species ◽  
Future Research ◽  
Change Scenario ◽  
Climate Change Scenarios ◽  
Ground Truth Data

Abstract In steep terrain, forests play an important role as natural means of protection against natural hazards, such as rockfall. Due to climate warming, significant changes in the protection service of these forests have to be expected in future. Shifts of current to more drought adapted species may result in temporary or even irreversible losses in the risk reduction provided by these forests. In this study, we assessed how the protective effect against rockfall of a protection forest in the western part of the Valais in the Swiss Alps may change in future, by combining dynamic forest modelling with a quantitative risk analysis. Current and future forest development was modelled with the spatially explicit forest model TreeMig for a moderate (RCP4.5) and an extreme (RCP8.5) climate change scenario. The simulated forest scenarios were compared to ground-truth data from the current forest complex. We quantified the protective effect of the different forest scenarios based on the reduction of rockfall risk for people and infrastructure at the bottom of the slope. Rockfall risk was calculated on the basis of three-dimensional rockfall simulations. The forest simulations predicted a clear decrease in basal area of most of the currently present species in future. The forest turned into a Q. pubescens dominated forest, for both climate scenarios, and mixed with P. sylvestris in RCP4.5. F. sylvatica completely disappeared in RCP8.5. With climate warming, a clear increase in risk is expected for both climate change scenarios. In the long-term (> 100 years), a stabilization of risk, or even a slight decline may be expected due to an increase in biomass of the trees. The results of this study further indicate that regular forest interventions may promote regeneration and thus accelerate the shift in species distribution. Future research should address the long-term effect of different forest management strategies on the protection service of forests under climate change.

Late Quaternary history of the Lake O'Hara region, British Columbia – an evaluation of sedimentation rates and bulk amino acid ratios in lacustrine records

1988 ◽  
Vol 25 (7) ◽  
pp. 1037-1048 ◽  
Author(s):  
Mel A. Reasoner ◽  
Nathaniel W. Rutter
Keyword(s):  
Amino Acid ◽  
Aspartic Acid ◽  
Sedimentation Rate ◽  
River Sediments ◽  
Sedimentation Rates ◽  
Rate Data ◽  
Radiocarbon Dates ◽  
Clastic Sediments ◽  
Lake Cores ◽  
Total Sedimentation

Lake O'Hara (subalpine) and Opabin Lake (alpine) are situated directly adjacent to a high section of the Continental Divide in the central Canadian Rocky Mountains. Core samples recovered from the lakes show a consistent stratigraphy comprising gyttja and underlying inorganic clastic sediments. The gyttja contains Bridge River (2350 years BP) and Mazama (6800 years BP) tephras and is separated from the lower clastic sediments by a sharp, conformable contact. Radiocarbon dates obtained from conifer needles, extracted from directly above the contact, indicate that deglaciation had proceeded upvalley from the O'Hara basin priorto ca. 10 100 years BP. Preliminary palaeobotanical and macrofossil data suggest that a Pinus–Abies forest with lesser Picea was established in the vicinity of Lake O'Hara by this time. Consequently, the minimum age of moraine systems situated downvalley from Lake O'Hara is Late Wisconsinan.Mean annual sedimentation rates were derived from sediment thickness data from 14 Lake O'Hara and 2 Opabin Lake cores. Averaged total sedimentation rate values from the Lake O'Hara cores are 0.13 mm/year (post-Bridge River), 0.13 mm/year (Mazama – Bridge River) and 0.05 mm/year (11 000 years BP – Mazama). Averaged total sedimentation rate values from the Opabin Lake cores are 0.19 mm/year (post-Bridge River), 0.07 mm/year (Mazama – Bridge River), and 0.06 mm/year (8530 years BP – Mazama). Higher total sedimentation rates in post-Bridge River sediments of Opabin Lake are presumably related to climatic conditions associated with more extensive upvalley ice during the last ca. 2300 years. Highly variable sedimentation rate data obtained from the Lake O'Hara cores suggest that the use of sedimentation rate data as a proxy record of upvalley glacial activity is inappropriate in the Lake O'Hara setting where inflowing glacial stream systems are interrupted by upvalley lake basins.Aspartic acid D/L ratios were derived from bulk gyttja samples of known age from seven Lake O'Hara and one Opabin Lake core. In all but two cases, aspartic acid D/L ratios increase consistently with respect to sediment age. The increasing downcore trends in the aspartic acid D/L ratios suggest the possibility of using amino acid data from bulk gyttja samples as a check for reworking in cases where chronostratigraphic markers are absent.

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.

scholarly journals Erosion index formulation with respect to reservoir life in the upper Citarum watershed

2018 ◽  
Vol 147 ◽  
pp. 03002
Author(s):  
Bakhtiar
Keyword(s):  
Sediment Yield ◽  
Assessment Tool ◽  
Average Value ◽  
Erosion Index ◽  
Dead Storage ◽  
The Mean ◽  
The Relationship ◽  
Water Assessment ◽  
Annual Sediment

This study aimed to formulate erosion index in the upper Citarum watershed with respect to the Saguling reservoir life. Soil and Water Assessment Tool model was incorporated to simulate hydrological processes in the catchment. From the calibration and validation results, the model is considerably of good performance. The simulated sediment inflow at Nanjung outlet was then extrapolated to determine the sediment inflow into the reservoir. The study revealed that the average value of sediment inflow into the reservoir is 29.24 tonnes/ha/year just below the tolerable erosion limit of 30 tonnes/ha/year assumed by Hammer (1981). It was also found that the relationship between sediment yield and sediment inflow is non linear. Erosion index is formulated as the ratio between the mean annual sediment yield generated in the watershed and the mean annual sediment yield that leads dead storage to be full in the designated life of the reservoir. Erosion index equals to 1.0 indicates that the dead storage will be full in the designated life of the reservoir. A classification of erosion index can be subsequently be made based on erosion index and reservoir life relationship.

scholarly journals A quasi-annual record of time-transgressive esker formation: implications for ice-sheet reconstruction and subglacial hydrology

2020 ◽  
Vol 14 (6) ◽  
pp. 1989-2004 ◽  
Author(s):  
Stephen J. Livingstone ◽  
Emma L. M. Lewington ◽  
Chris D. Clark ◽  
Robert D. Storrar ◽  
Andrew J. Sole ◽  
...  
Keyword(s):  
High Resolution ◽  
Mathematical Models ◽  
Ice Sheet ◽  
Laurentide Ice Sheet ◽  
Sediment Fluxes ◽  
General Record ◽  
True Measure ◽  
Annual Sediment ◽  
Subglacial Drainage

Abstract. We identify and map chains of esker beads (series of aligned mounds) up to 15 m high and on average ∼ 65 m wide in central Nunavut, Canada, from the high-resolution (2 m) ArcticDEM. Based on the close 1 : 1 association with regularly spaced, sharp-crested ridges interpreted as De Geer moraines, we interpret the esker beads to be quasi-annual ice-marginal deposits formed time-transgressively at the mouth of subglacial conduits during deglaciation. Esker beads therefore preserve a high-resolution record of ice-margin retreat and subglacial hydrology. The well-organised beaded esker network implies that subglacial channelised drainage was relatively fixed in space and through time. Downstream esker bead spacing constrains the typical pace of deglaciation in central Nunavut between 8.1 and 6.8 cal kyr BP to 165–370 m yr−1, although with short periods of more rapid retreat (> 400 m yr−1). Under our time-transgressive interpretation, the lateral spacing of the observed eskers provides a true measure of subglacial conduit spacing for testing mathematical models of subglacial hydrology. Esker beads also record the volume of sediment deposited from conduits in each melt season, thus providing a minimum bound on annual sediment fluxes, which is in the range of 103–104 m3 yr−1 in each 6–10 km wide subglacial conduit catchment. We suggest that the prevalence of esker beads across this predominantly marine-terminating sector of the Laurentide Ice Sheet is a result of sediment fluxes that were unable to backfill conduits at a rate faster than ice-margin retreat. Conversely, we hypothesise that esker ridges form when sediment backfilling of the subglacial conduit outpaced retreat, resulting in headward esker growth close to but behind the margin. The implication, in accordance with recent modelling results, is that eskers in general record a composite signature of ice-marginal drainage rather than a temporal snapshot of ice-sheet-wide subglacial drainage.

Temporal variability of annual suspended sediment yield estimates and their uncertainties

2021 ◽  
Author(s):  
Aron Slabon ◽  
Thomas Hoffmann
Keyword(s):  
Suspended Sediment ◽  
Sediment Yield ◽  
Temporal Variability ◽  
Catchment Area ◽  
Sediment Load ◽  
Sampling Interval ◽  
Suspended Sediment Transport ◽  
River Rhine ◽  
The Impact ◽  
Annual Sediment

&lt;p&gt;Suspended sediment contributes to the vast majority of the annual sediment load transported by rivers to the global oceans. At the same time, this large fraction is transported just in a fraction of time. Towards achieving sustainable sediment management and healthy fluvial systems, identifying the impact of the temporal variability on annual load estimates becomes indispensable in order to reduce uncertainties.&lt;/p&gt;&lt;p&gt;We aim to estimate the temporal variability of suspended sediment transport and the uncertainty of annual suspended sediment loads. Our approach is based on high-resolution time series (15 min sampling interval) of discharge and suspended sediment concentration (SSC) at four monitoring stations with different degrees of discharge variability. The quantification of the variability of discharge and sediment yield is achieved through the exceedance time. The uncertainty of the annual sediment load is estimated using a bootstrap approach. We assess the impact of the sampling interval and link the optimal sampling interval to different SSC-variability. Further, the impact of rating parameters on the uncertainty of annual loads is investigated.&lt;/p&gt;&lt;p&gt;Our results indicate an increase in SSC-variability with decreasing discharge, leading to a negative relationship with the contributing catchment area. The 80 % exceedance times for the annual sediment load range from less than 10 % for the river Ammer (catchment area 608 km&amp;#178;) between 10 &amp;#8211; 20 % for the rivers Ilz (765 km&amp;#178;) and Moselle (27 088 km&amp;#178;) to more than 40 % for the river Rhine (109 806 km&amp;#178;). Simultaneously, the variability increases with a decrease in sampling frequency. Our preliminary results indicate a negative exponential relationship between exceedance time and uncertainties in annual load estimates. This relationship can be used to estimate the uncertainty of annual loads estimated based on low frequency sediment sampling at the continental to global scale.&lt;/p&gt;

scholarly journals Modelling mean annual sediment yield using a distributed approach

2001 ◽  
Vol 26 (11) ◽  
pp. 1221-1236 ◽  
Author(s):  
Anton J. J. Van Rompaey ◽  
Gert Verstraeten ◽  
Kristof Van Oost ◽  
Gerard Govers ◽  
Jean Poesen
Keyword(s):  
Sediment Yield ◽  
Distributed Approach ◽  
Annual Sediment
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