Estimating the Sediment Flux and Budget for a Data Limited Rift Valley Lake in Ethiopia

Information on sediment concentration in rivers is important for the design and management of reservoirs. In this paper, river sediment flux and siltation rate of a rift valley lake basin (Lake Ziway, Ethiopia) was modeled using suspended sediment concentration (SSC) samples from four rivers and lake outlet stations. Both linear and non-linear least squares log–log regression methods were used to develop the model. The best-fit model was tested and evaluated qualitatively by time-series plots, quantitatively by using watershed model evaluation statistics, and validated by calculating the prediction error. Sediment yield (SY) of ungauged rivers were assessed by developing and using a model that includes catchment area, slope, and rainfall, whereas bedload was estimated. As a result, the gross annual SY transported into the lake was 2.081 Mton/year. Annually, 0.178 Mton/year of sediment is deposited in floodplains with a sediment trapping rate of 20.6%, and 41,340 ton/year of sediment leaves the lake through the Bulbula River. The annual sediment deposition in the lake is 2.039 Mton/year with a mean sediment trapping efficiency of 98%. Based on the established sediment budget with average rainfall, the lake will lose its volume by 0.106% annually and the lifetime of Lake Ziway will be 947 years. The results show that the approach used can be replicated at other similar ungauged watersheds. As one of the most important sources of water for irrigation in the country, the results can be used for planning and implementing a lake basin management program targeting upstream soil erosion control.

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Ultra-High-Resolution Monitoring of the Catchment Response to Changing Weather Conditions Using Online Sediment Trapping

Quaternary ◽

10.3390/quat2020018 ◽

2019 ◽

Vol 2 (2) ◽

pp. 18 ◽

Cited By ~ 2

Author(s):

Markus Johansson ◽

Saija Saarni ◽

Jouni Sorvari

Keyword(s):

High Resolution ◽

Wind Speed ◽

Sediment Trap ◽

Winter Season ◽

Weather Conditions ◽

Sediment Flux ◽

Urban Site ◽

Lake Basin ◽

Flux Rate ◽

Sediment Trapping

The purpose of this study was to identify relationships between meteorological and hydrological observations and sediment flux rate changes, in order to better understand catchment dynamics. The meteorological and hydrological observations included local air temperature, wind speed, water temperature, and ice cover, while the sediment flux rate was observed in the lake basin using a modified sediment trap technique. This study demonstrates the advantages of a new online methodology applied in conventional sediment trapping to obtain flux rate information with daily resolution. A prototype of a high-resolution online sediment trap was tested in Savilahti Bay, Lake Kallavesi, eastern Finland, during the period from 22 October 2017 to 6 October 2018. The daily resolutions of meteorological, hydrological, and sediment flux rate data were analyzed using statistical methods. The results indicate relationships between temperature, precipitation, wind speed, and sediment flux rate, but the urban site also showed erosional changes due to anthropogenic land use. Sediment flux ceased during winter season and spring floods were recorded as pronounced peaks in sediment flux, while the growing season showed generally higher sediment accumulation rates. This research also provides valuable information on the catchment response to short-term weather events. The influence of a storm led to larger sediment flux for several days. The importance of wind speed and frost formation on sedimentation, which has been difficult to address due to trap deployment times of typically several months, is now supported. Used together with varved sediment archives, online sediment trapping will facilitate the interpretation of paleoclimatic proxy records and modeling of detailed weather and erosion conditions that are related to climate change.

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Experimental Study on the Impact of Slope and Silt-laden inflow Conditions on Vegetation Sediment Trapping Process

10.5194/egusphere-egu2020-5373 ◽

2020 ◽

Author(s):

Mingjie Luo ◽

Chengzhong Pan ◽

Chunlei Liu

Keyword(s):

Flow Rate ◽

Influencing Factor ◽

Stable State ◽

Sediment Concentration ◽

Trapping Efficiency ◽

Sediment Trapping ◽

Sediment Delivery ◽

Trapping Effect ◽

The Impact ◽

Trapping Process

Vegetation-restored hillslope surfaces not only reduce erosion but they also remove sediment from upslope silt-laden inflow. To investigate the sediment trapping effect of grassland, this study conducted a series of crossed sediment trapping experiments that examined various factors, such as slope (5&#176;&#8211;20&#176;), sediment concentration (40&#8211;160 g L&#8722;1), and unit flow rate (7.5&#8211;45.0 L min&#8722;1 m&#8722;1). The duration of each experiment was longer than required to reach the stable state of sediment trapping, so we measured and verified the individual sediment trapping capacity (Rm) by experiments. The results showed that gentler slopes generated higher instantaneous sediment trapping efficiency (ISTE) and greater Rm. As the sediment concentration of the silt-laden inflow increased, the impact of slope on Rm increased. Higher sediment concentration led to lower ISTE but greater Rm. Similar to the effect of sediment concentration, a larger unit flow rate led to lower ISTE and greater Rm. Thus, it is evident that interaction among these factors affects sediment trapping process. The experiments revealed the greatest sediment trapping effect of grass strips was concentrated mainly in the first 2-m width, and that 90% of sediment deposition occurred within half the time needed to reach the stable state. Slope and flow rate were found to have an effect on sediment trapping in each section of grass strips, whereas the effect of sediment concentration was concentrated primarily in the first 5-m width. Standard regression coefficients of a comprehensive regression analysis showed that the intensities of the influencing factors on Rm were as follows: slope (0.736) > grassland width (0.498) > unit flow rate (0.398) > sediment concentration (0.240). It was established that slope is the strongest influencing factor, and that sediment concentration and unit flow rate mainly affect Rm by changing the rate of sediment delivery. These results will help expand the theoretical basis regarding the effects of vegetation restoration on watersheds in soil erosion research.

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Insights on the Impacts of Hydroclimatic Extremes and Anthropogenic Activities on Sediment Yield of a River Basin

Earth ◽

10.3390/earth2010003 ◽

2021 ◽

Vol 2 (1) ◽

pp. 32-50

Author(s):

Rocky Talchabhadel ◽

Jeeban Panthi ◽

Sanjib Sharma ◽

Ganesh R. Ghimire ◽

Rupesh Baniya ◽

...

Keyword(s):

Suspended Sediment ◽

River Basin ◽

Extreme Precipitation ◽

Suspended Sediment Concentration ◽

Anthropogenic Activities ◽

Sediment Concentration ◽

Sediment Flux ◽

Mountain River ◽

Ecological Processes ◽

Precipitation Indices

Streamflow and sediment flux variations in a mountain river basin directly affect the downstream biodiversity and ecological processes. Precipitation is expected to be one of the main drivers of these variations in the Himalayas. However, such relations have not been explored for the mountain river basin, Nepal. This paper explores the variation in streamflow and sediment flux from 2006 to 2019 in central Nepal’s Kali Gandaki River basin and correlates them to precipitation indices computed from 77 stations across the basin. Nine precipitation indices and four other ratio-based indices are used for comparison. Percentage contributions of maximum 1-day, consecutive 3-day, 5-day and 7-day precipitation to the annual precipitation provide information on the severity of precipitation extremeness. We found that maximum suspended sediment concentration had a significant positive correlation with the maximum consecutive 3-day precipitation. In contrast, average suspended sediment concentration had significant positive correlations with all ratio-based precipitation indices. The existing sediment erosion trend, driven by the amount, intensity, and frequency of extreme precipitation, demands urgency in sediment source management on the Nepal Himalaya’s mountain slopes. The increment in extreme sediment transports partially resulted from anthropogenic interventions, especially landslides triggered by poorly-constructed roads, and the changing nature of extreme precipitation driven by climate variability.

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Conceptual model of sedimentgraph from flood events in a small agricultural watershed

Annals of Warsaw University of Life Sciences – SGGW Land Reclamation ◽

10.2478/v10060-008-0004-7 ◽

2008 ◽

Vol 39 (1) ◽

pp. 49-57 ◽

Cited By ~ 1

Author(s):

Kazimierz Banasik ◽

J. Mitchell

Keyword(s):

Conceptual Model ◽

Suspended Sediment ◽

Sediment Concentration ◽

Agricultural Watershed ◽

Sediment Flux ◽

Flood Events ◽

Rainfall Events ◽

Sediment Routing ◽

Suspended Sediment Flux ◽

Lag Times

Conceptual model of sedimentgraph from flood events in a small agricultural watershed A procedure for predicting the sediment graph (i.e. the suspended sediment flux), from a small river catchment by heavy rainfall, has been developed using the concept of an instantaneous unit hydrograph (IUH) and dimensionless sediment concentration distribution (DSCD). A formula for instantaneous unit sedimentgraph (IUSG) is presented, and a procedure for estimating the sediment routing coefficient, which is a key parameter of the IUSG, based on measured data of rainfall-runoff-suspended sediment is applied. Field data from a small, field sized agricultural basin, lacated in center of Illinois has been used for analizing lag times for runoff (LAG) and sediment yield (LAGs). Assumptions about sediment generated during rainfall events are discussed.

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Characterizing and modelling the trapping efficiency of sedimentation basins downstream of harvested peat bog

Canadian Journal of Civil Engineering ◽

10.1139/cjce-2017-0330 ◽

2018 ◽

Vol 45 (6) ◽

pp. 478-488 ◽

Cited By ~ 1

Author(s):

Myriam Samson-Dô ◽

André St-Hilaire

Keyword(s):

Suspended Sediment Concentration ◽

Suspended Sediments ◽

Sediment Concentration ◽

Drainage Water ◽

Organic Content ◽

Trapping Efficiency ◽

Peat Moss ◽

Decomposition Level ◽

In Series ◽

Sedimentation Basins

Peat moss harvesting is an important industry in Canada. To harvest peat, the water table of the peatland must be lowered to allow the surficial peat layer to dry and be harvested. Drainage water can contain suspended sediments, so at most harvesting sites, the water is routed through sedimentation basins. This work focuses on characterizing and modelling their trapping efficiency. Eight basins with different volume/watershed area ratios (705 to 4170 m3/km2) were studied in three Quebec regions. Suspended sediment concentration and discharge were monitored up- and downstream of each basin during the ice-free season. Basins with high ratios of volume/drainage area, multiple basin configurations (i.e., two basins in series or in parallel), and those equipped with a flow regulation structure were more efficient than regular basins. Moreover, the nature of sediments (size, decomposition level, and organic content) influences loads, but not the trapping efficiency. Finally, two empirical models developed to predict trapping efficiency of municipal sedimentation basins were tested and adapted for basins that capture peat sediments.

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An Uncertainty Estimation Framework to Quantify the Water Balance of Ethiopian Rift Valley Lake basin

10.5194/egusphere-egu21-5014 ◽

2021 ◽

Author(s):

Tesfalem Abraham ◽

Yan Liu ◽

Sirak Tekleab ◽

Andreas Hartmann

Keyword(s):

Water Balance ◽

Rift Valley ◽

Water Resource Management ◽

Management Strategies ◽

Lake Basin ◽

Climatic Data ◽

Ungauged Catchments ◽

Regional Regression ◽

Validation Parameters ◽

Global Precipitation

In Ethiopia, more than 80% of big freshwater lakes are located in the Rift Valley Lake Basin, which is serving for multipurpose water use of over 30 million people. The basin is one of the most densely populated regions in Ethiopia and it covers an area of 53,035 km2. However, most of the catchments recharging these lakes are ungauged and their water balance is not well quantified, and hence, limiting the development of appropriate water resource management strategies. Prediction for ungauged catchments has demonstrated its effectiveness in hydro-climatic data-rich regions. However, these approaches are not well evaluated in the climatic data-limited condition and the consecutive uncertainty emerging in the small catchments is not adequately quantified. In this study, we use the HBV model to simulate streamflow using global precipitation and potential evapotranspiration products as forcings. We develop and apply a Monte-Carlo scheme to calibrate the model and quantify uncertainty at 16 catchments in the basin where gauging stations are available. Out of these, we use 14 best catchments to derive the best regional regression model by correlating the best calibration parameters, the best validation parameters, and parameters that give the most stable predictions with catchment attributes that are available throughout the basin. A weighting scheme in the regional regression accounts for parameter uncertainty in the calibration. A spatial cross-valuation that is applied 14 times always leaving out one of the gauged catchments provides 14 regional regression functions that express uncertainty regionalization. It also shows that the regionalization procedure that uses the best validation parameters for regionalization provides the most robust results. We then subsequently apply the 14 spatial regression functions of the cross-validation to the remaining 35 ungauged catchments in the Rift Valley Lake Basin to provide regional water balance estimations including quantification of regionalization uncertainty. With these results, our study provides a new procedure to use global precipitation and evapotranspiration products to predict and evaluate streamflow simulation for hydro-climatically data scares regions considering uncertainty. It, therefore, enhances the confidence in the understanding of water balance in those regions and will support the planning and development of appropriate water resource management strategies.&#160;Keywords: Parameters Estimation, Uncertainties, Ungauged Catchment, Weighted Regression, Water Balance

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Correction: Aga, A.O. et al. Estimating the Sediment Flux and Budget for a Data Limited Rift Valley Lake in Ethiopia. Hydrology 2019, 6, 1

Hydrology ◽

10.3390/hydrology7010003 ◽

2019 ◽

Vol 7 (1) ◽

pp. 3

Author(s):

Alemu O. Aga ◽

Assefa M. Melesse ◽

Bayou Chane

Keyword(s):

Rift Valley ◽

Sediment Flux

The authors wish to make the following corrections to this paper (Aga et al [...]

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Influence of Permeability on Sediment Trapping Efficiency in an ELJ Groyne Field

World Environmental and Water Resources Congress 2019 ◽

10.1061/9780784482353.022 ◽

2019 ◽

Author(s):

J. A. Bautista ◽

J. M. Kuroiwa ◽

J. F. Huamán ◽

L. F. Castro

Keyword(s):

Trapping Efficiency ◽

Sediment Trapping

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CALCULATION OF THE RATE OF NET ON-OFFSHORE SEDIMENT TRANSPORT ON THE BASIS OF FLUX CONCEPT

Coastal Engineering Proceedings ◽

10.9753/icce.v19.91 ◽

1984 ◽

Vol 1 (19) ◽

pp. 91 ◽

Cited By ~ 2

Author(s):

Ichiro Deguchi ◽

Toru Sawaragi

Keyword(s):

Sediment Transport ◽

Water Depth ◽

Sediment Concentration ◽

Suspended Load ◽

Spatial Variations ◽

Sediment Flux ◽

Bed Load ◽

Two Dimensional ◽

Dimensional Model ◽

Two Dimensional Model

Time and spatial variations of sediment concentration of both bed load and suspended load in the process of two-dimensional beach deformation were investigated experimentally. At the same time, the relation between the velocities of water-particle and sediment migration was analyzed theoretically. By using those results,a net rate of on-offshore sediment_ transport in the process of two-dimensional model beach deformation qf was calculated on the basis of sediment flux. It is found that Qf coincides fairly well with .the net rate of on-offshore sediment transport calculated from the change of water depth.

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