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 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.

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.

3D hydro-morphodynamic models as support tools for obtaining sustainable sediment management strategies of reservoirs

2020 ◽  
Author(s):  
Kilian Mouris ◽  
Leon Saam ◽  
Felix Beckers ◽  
Silke Wieprecht ◽  
Stefan Haun
Keyword(s):  
Sediment Transport ◽  
Water Level ◽  
Management Strategies ◽  
Sediment Management ◽  
Transport Processes ◽  
Water Levels ◽  
Hydraulic Structures ◽  
Suspended Sediment Transport ◽  
Reservoir Sedimentation ◽  
Bottom Outlets

&lt;p&gt;Reservoir sedimentation reduces not only the available storage volume of reservoirs, but may also create other serious problems, such as an increase of bed levels or accumulations of nutrients and contaminants, which affect the environment. An increase in bed levels at the head of the reservoir can reduce flood safety and increase the risk for the surrounding areas. Deposited sediments close to the dam may block hydraulic structures, such as the bottom outlets, or, in case they enter the intake, lead to possible abrasion of plant components (e.g. wear of turbines and pipes).&lt;/p&gt;&lt;p&gt;Prior to reservoir construction, a pre-evaluation of the sediment yield from the catchment is usually performed by using soil erosion and sediment delivery models. However, the trapping efficiency is often only obtained by empirical approaches, such as Brune&amp;#8217;s or Churchill&amp;#8217;s curve, which are based on the capacity of the reservoir and the mean annual inflow. This is still common practice, although 3D hydro-morphodynamic models became powerful tools to numerically study sediment transport and reservoir sedimentation prior to the construction of reservoirs as well as during its operation.&lt;/p&gt;&lt;p&gt;Within this study, a fully 3D hydro-morphodynamic numerical model, based on the Reynolds-averaged Navier-Stokes equations, is applied to a case study to simulate, on the one hand suspended sediment transport within a hydropower reservoir and on the other hand a reservoir flushing operation as potential management scenario, with the goal to remobilize already deposited sediments and to release these sediments from the reservoir. The modeled reservoir has a total storage capacity of around 14 million m&amp;#179;, whereby the water level can fluctuate due to pumped-storage operation by 40.5&amp;#160;m (difference between the maximum operation level and the operational outlet). At the head is the natural inflow of two creeks into the reservoir and a lateral transition tunnel is located on the orographic right side, which collects several headwater streams from adjacent catchments.&lt;/p&gt;&lt;p&gt;Simulations are performed for different operation modes of the reservoir. The results clearly show that through active reservoir management (variation of water levels as well as using the momentum of the discharge from the transition tunnel) the sediment motion in the reservoir can be affected to a certain extent. It is for instance possible to almost completely avoid reservoir sedimentation in front of the dam and the hydraulic structures (water intake and bottom outlets) during sediment-laden flows when simultaneously high discharges are provided from the laterally located transition tunnel. The conducted simulation results of reservoir flushing also show that the success of the flushing operation is strongly dependent on the water level. As expected, flushing with full drawdown of the water level is the most efficient method to release sediments.&lt;/p&gt;&lt;p&gt;Through the detailed results of the 3D hydro-morphodynamic model, it is feasible to receive a deeper knowledge of the ongoing sediment transport processes within the studied reservoir. The gained knowledge can further be used to derive sustainable and efficient management strategies for the sediment management of the reservoir.&lt;/p&gt;

scholarly journals Reservoir sedimentation regime analysis: case study of Kedungombo reservoir and Sermo reservoir

2021 ◽  
Vol 27 (1) ◽  
pp. 80-87
Author(s):  
Indri Rahmandhani Fitriana ◽  
Djoko Legono ◽  
Heriantono Waluyadi
Keyword(s):  
Sedimentation Rate ◽  
Characteristic Curve ◽  
Digital Terrain Model ◽  
Reservoir Sedimentation ◽  
Terrain Model ◽  
Basic Services ◽  
Sedimentation Volume ◽  
Dead Storage ◽  
The Dead ◽  
Sedimentation Regime

The Kedungombo and the Sermo Reservoirs have problems in fulfilling basic services because of sedimentation. Sedimentation that occurs in each of the reservoirs would form a specific reservoir sedimentation pattern that is supposed to be similar because the hydrology and physiography conditions of the reservoir's catchment area are similar. This study aims to determine the dynamics of sedimentation patterns that occur in the dead storage for reviewing the characteristics/sedimentation regime of the two reservoirs. The analysis was carried out by processing bathymetrical data which were processed into a digital terrain model (DTM) using ArcGIS. Furthermore, the storage volume, sedimentation volume, storage percentage, and specific reservoir sedimentation rate are calculated. The results showed that the two reservoirs showed an increase in sedimentation volume each year so that the reservoir characteristic curve shifted from the plan graph. The dead storage capacity of Kedungombo Reservoir is 100% in 1989 to 43% in 2016 and 100% of Sermo Reservoir in 1997 to 58% in 2011. The specific reservoir sedimentation rate, i.e. 0.0031 and 0.0042 million m3/year/km2 for the Kedungombo Reservoir (between 1989 and 2016) and the Sermo Reservoir (between 1997 and 2011) respectively, indicating that the two reservoirs are in the same regime

scholarly journals Modelling and forecasting reservoir sedimentation of irrigation dams in the Guinea Savannah Ecological Zone of Ghana

2021 ◽  
Author(s):  
Thomas Apusiga Adongo ◽  
Felix K. Abagale ◽  
Wilson A. Agyare
Keyword(s):  
Control Measures ◽  
Annual Rainfall ◽  
Reservoir Sedimentation ◽  
Back Propagation Algorithm ◽  
Ecological Zone ◽  
Exponential Regression ◽  
Sediment Volume ◽  
Feed Forward Back Propagation ◽  
Input Parameters ◽  
Annual Sediment

Abstract Effective management of reservoir sedimentation requires models which can predict sedimentation of the reservoirs. In this study, linear regression, non-linear exponential regression and artificial neural network models have been developed for the forecasting of annual storage capacity loss of reservoirs in the Guinea Savannah Ecological Zone (GSEZ) of Ghana. Annual rainfall, inflows, trap efficiency and reservoir age were input parameters for the models whilst the output parameter was the annual sediment volume in the reservoirs. Twenty (20) years of reservoirs data with 70% data used for model training and 30% used for validation. The ANN model, the feed-forward, back-propagation algorithm Multi-Layer Perceptron model structure which best captured the pattern in the annual sediment volumes retained in the reservoirs ranged from 4-6-1 at Karni to 4-12-1 at Tono. The linear and nonlinear exponential regression models revealed that annual sediment volume retention increased with all four (4) input parameters whilst the rate of sedimentation in the reservoirs is a decreasing function of time. All the three (3) models developed were noted to be efficient and suitable for forecasting annual sedimentation of the studied reservoirs with accuracies above 76%. Forecasted sedimentation up to year 2038 (2019–2038) using the developed models revealed the total storage capacities of the reservoirs to be lost ranged from 13.83 to 50.07%, with 50% of the small and medium reservoirs filled with sediment deposits if no sedimentation control measures are taken to curb the phenomenon.

scholarly journals Numerical Modeling of turbidity currents with Ansys CFX and Telemac 3D

2018 ◽  
Vol 40 ◽  
pp. 03014 ◽  
Author(s):  
Magali Jodeau ◽  
Sabine Chamoun ◽  
Jiawei Feng ◽  
Giovanni De Cesare ◽  
Anton J. Schleiss
Keyword(s):  
Numerical Modeling ◽  
Experimental Work ◽  
Turbidity Current ◽  
Turbidity Currents ◽  
Reservoir Sedimentation ◽  
Engineering Teams ◽  
Fine Sediments ◽  
First Case ◽  
Ansys Cfx

Turbidity currents may be a relevant lever to manage the accumulation of fine sediments in reservoirs. In this paper, we propose to show how two different numerical codes simulate the propagation of turbidity currents. Telemac 3D and Ansys CFX 17.1 solver were chosen as they are commonly used by many research and engineering teams. The simulations are performed on two configurations. The first case aims at modeling the plunging of a turbidity current. The second model is validated based on an experimental work performed at EPFL. The latter consisted on testing turbidity current venting as a solution to manage reservoir sedimentation. A long and narrow flume was used to simulate the reservoir where a turbidity current was triggered. The advantages and limits of both approaches are discussed in order to supply guidelines for the modeling of turbidity currents in real reservoirs.

Analysis of Application of Sediment Trap in Rivers as An Effort Reservoir Sedimentation Control

2021 ◽  
Vol 26 (2) ◽  
pp. 229-236
Author(s):  
Dyah Ari Wulandari ◽  
Desyta Ulfiana ◽  
Priyo Nugroho Parmantoro
Keyword(s):  
Sediment Trap ◽  
Sediment Load ◽  
Sediment Traps ◽  
Fine Sediment ◽  
Sediment Deposition ◽  
Reservoir Sedimentation ◽  
Check Dam ◽  
Fine Sediments ◽  
Irrigation Channels ◽  
Selection Of

Reservoir sedimentation can be overcome by reducing the amount of sediment that enters the reservoir, by building check dam. The check dam has more deposited coarse sediment load than fine sediment load. Fine sediment that escapes the check dam will flow further and eventually enter the reservoir pond. Therefore it is necessary to build a building that can capture fine sediments. Construction is planned as a system of sediment trap in irrigation channels. The purpose of this study is to analyze the possibility of applying the sediment trap in the river to deposit sediments that escape the check dam. The analysis begins with the selection of the location of the sediment trap, then calculate the dimensions of the sediment trap and the amount of sediment that has settled. Based on the analysis of the selected dimensions with several combinations of gradation of sediment grains, sediment deposition that occurs ranges from 42 - 68%. So it can be concluded making the sediment trap in the river can be done. However, for the application of these sediment traps further research is needed regarding the dimensions of sediment traps that are most optimal for sediment deposition.

scholarly journals Coastal sediment balance in the eastern part of the Gulf of Riga (2005–2016)

Baltica ◽  
2018 ◽  
Vol 30 (2) ◽  
pp. 87-95 ◽  
Author(s):  
Jānis Lapinskis
Keyword(s):  
Coastal Sediment ◽  
Eastern Coast ◽  
Storm Event ◽  
Fine Sediments ◽  
Coastal Slope ◽  
Sediment Volume ◽  
Quantitative Estimates ◽  
Sediment Balance ◽  
Gulf Of Riga ◽  
Coastal Retreat

A hurricane known as Ervin or Gudrun travelled over Latvia in 8–9 January, 2005. As a result of severe SW and W winds, as well as lack of sea ice, clearly pronounced changes in the distribution of coastal sediment has been induced. Cross-shore profile leveling at various time instants was used to obtain quantitative estimates of the amount of accumulated sediments. The total volume of sediments eroded from the subaerial part of coastal slope reached 0.8 million m3. This paper represents assessment of consequent changes and coastal slope “rebuilding” success after this storm event. The data indicates lack of significant overall net loss of subaerial sediment volume along the most part of the eastern coast of the Gulf of Riga. Significant primary dune growth and beach accumulation is mostly limited to southernmost part of assessed coastal stretch. Total volume of fine sediments in beach and primary dunes still is 5 % lower than before erosion event of 2005. Erosion vulnerability and total length of coastal sections that are expected to be a subject to future coastal retreat is increasing.

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.

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