Modelling of sedimentation processes inside Roseires Reservoir (Sudan)

Abstract

Abstract. Roseires Reservoir, located on the Blue Nile River, in Sudan, is the first trap to the sediments coming from the upper catchment in Ethiopia, which suffers from high erosion and desertification problems. The reservoir lost already more than one third of its storage capacity due to sedimentation in the last four decades. Appropriate management of the eroded area in the upper basin could mitigate this problem. In order to do that, the areas providing the highest sediment volumes to the river have to be identified, since they should have priority with respect to the application of erosion control practices. This requires studying the sedimentation record inside Roseires Reservoir, with the aim of identifying when and how much sediment from a certain area is deposited. The identification of deposition time is derived from soil stratification inside the reservoir. This requires expensive coring campaigns that need to be optimized. The most promising sampling coring areas were therefore selected beforehand by combining bathymetric data and the results of a depth-averaged morphodynamic model able to record vertical stratification in sediment deposits. The model allowed recognising the areas that are potentially neither subject to net erosion nor to bar migration during the life span of the reservoir. Verification of these results was carried out by analysing sediment stratification from the data collected in subsequent field campaign.

Modelling the Inundation and Morphology of the Seasonally Flooded Mayas Wetlands in the Dinder National Park-Sudan

“…Typically, only a subset of the parameters can be estimated due to restrictions imposed by the model structure, lack of measurements, and limited data. In this study, the various model parameters were adopted from previous literature from the region (e.g., Omer et al 2015). Then, manual calibration through adjusting the model topography and the Manning roughness parameter in an iterative way until the observed water level exhibited an acceptable level of agreement with model output.…”

“…A practical approach is to estimate such parameters from available process data or from the literature. Therefore, the various morphological model parameters were adopted from previous literature from the region (i.e., Omer et al 2015). The adopted parameters are presented in Table 1.…”

“…11a-b). With such average flow, the Maya is partially inundated with variable water depths according to the Maya's topography with a maximum depth of 3.5 m. Other parts Table 1 Values of physical parameters adopted from (Omer et al 2015) Physical parameter Calibrated value Spiral flow -(β) 0 . 5 ( −) Horizontal eddy viscosity 1.0 (m 2 s −1 ) Horizontal eddy diffusivity 1.0 (m 2 s −1 ) Specific density of sediment 2650 (kg m −3 ) C soil (reference density of hindering settling) 1600 (kg m −3 ) D 50 355 μm Dry density of sand 2000 (kg m −3 ) Dry density of silt (deposited suspended solids) 1200 (kg m −3 ) Ws,0 (settling velocity of suspended solids) 0.005 (mm s −1 ) τ c (critical shear stress for erosion of silt) 1 (N m −2 ) τ d (critical shear stress for deposition of suspended solids) 1000 (N m −2 ) M (erosion rate of deposited silt) 2 (mg m −2 s −1 ) Manning roughness (n) 0.035 of the floodplain remain dry with no connection with the river water.…”

Untitled

“…The Blue Nile after leaving Lake Tana, quickly descends into a deep gorge until it enters the Sudan south of Roseires with average annual flow of 46.2×10 9 m 3 yr -1 . Before entering the Sudan plains, the Blue Nile receives 14 major torrential tributaries which supply most of the silty river water received at Roseires reservoir (Omer et al 2015).…”

The effect of optimism bias and governmental action on siltation management within Japanese reservoirs surveyed via artificial neural network

“…Notwithstanding manifold siltation predictions and elaborate simulation models (Ghimire & DeVantier, 2016;Hao, Qiu, & Li, 2017;Omer, Ali, Roelvink, Paron, & Crosato, 2015;Simoes & Yang, 2006;Zeleke, Moussa, & El-Manadely, 2013), the global development insinuates that planners, operators and practitioners struggle to predict both the sediment inflow and yield reservoirs correctly. Consequently, the implementation of suitable management strategies for siltation remains a challenge (de Vente et al, 2013;Kantoush & Sumi, 2017;Schleiss, Franca, Juez, & De Cesare, 2016;Yang, 2013), which prevails regardless of the respective environment, climate, society and technology level Annandale (2013); Basson (2009); Schleiss, De Cesare, and Althaus (2010).…”