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ABSTRACTSedimentation at intakes of drinking water treatment plants (DWTPs) clogs intake pipe inlets causing interruption of water supply and serious pump abrasion. It occurs due to river flow velocity (FV) decline which causes flow inability to carry sediment particles. On the other hand, high velocities increase water turbidity because they induce flow turbulence that diffuses bed sediment particles over the water depth. The diffusion causes turbid water withdrawal and consequent high treatment running cost. This paper aims to adjust FVs near DWTP intakes using river training works (TWs) to control sedimentation and turbidity. Road El-Farag DWTP intake was taken as a case study. Groin construction and riverbed dredging were proposed as effective TWs. A 2-D mathematical model (SMS) was used to simulate different scenarios of the TWs. The simulations aimed to increase the FVs near the intake area provided that they neither allow sedimentation nor bed scour. The study area with FVs ranging from 0.025 to 0.40 was simulated in a physical flume to investigate the corresponding water turbidity (WT) values. A Jar test was conducted to find a relationship between WT and alum doses at different FVs. This relationship determines the optimum alum dose that can minimize turbidity. SMS and flume simulations revealed that positioning of groins on the river bank opposite to the intake area combined with dredging near the intake managed to increase FVs that can prevent sedimentation and bed scour. Finally, a mathematical relationship between alum doses and FVs was established.

ABSTRACTThis paper aims to develop a computational model to assess and evaluate the annual water level fluctuation (WLF) impacts and their trends along any open channel (river, canal or lake) and provide reliable information that may help handle their implications. The impacts are related to water recession, flood plain areas, uncovered river bars and islands, locations of navigation bottle necks, and dredging works. The model is developed using Excel Spreadsheet VBA Coding. It computes the horizontal and inclined recession distances that govern water in take construction. It also computes the uncovered flood plain areas along the river reach to avoid encroachments and human interventions. In addition, it identifies the number of bar sand islands that emerge at low water levels to protect them against infringements. It also determines the locations of navigation bottle necks and computes the dredge volumes required. It can handle long river reaches quickly. Moreover, it is open-accessed where no hard locks or license renewals are required. It is run on Microsoft Excel which is an available and familiar environment to engineers. Therefore, the model can be a quick and powerful tool to support the decision-making process for projects related to such impacts, especially at the prefeasibility study stages. Reach '1' of River Nile in Egypt was taken as a case study to apply the model and show its capabilities in assessing the WLF impacts. This could help compute and analyze the size of the impacts and conceive their trends. Finally, the model could provide information about the impacts in concrete figures which can support decision making in coping properly with the impacts.

The current research aims to study the suitability of Damietta branch meanders for safe first-class cargo transportation. This branch is the River Nile eastern waterway bifurcated at the beginning of the Delta region, which is about 22.0 km downstream of El-Roda gauge in Cairo. It extends for 244 km to the Mediterranean Sea. The branch plan form was examined for meanders. Fifty-one meanders could be identified throughout. Their characteristics were analyzed. The results revealed the existence of eight sharp meanders and seven critical looping ones that would slow down and jeopardize the first-class navigation traffic. Also, it was found that about 68 % of the looping meander lengths could be saved if cut-offs were executed. Accordingly, examples of straightening the river at four meanders were proposed for clarification. It was found that their lengths could be reduced by 51.10 %. Finally, the study concluded that in order for the Damietta branch to be qualified and entitled to safe first-class cargo transportation, the sharp meanders and critical loops have to be subject to training works and re-channelized.