Hydraulic Engineering

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Browsing Hydraulic Engineering by Author "Agizew, Nigussie (PhD)"

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    Adopting Landscape Infrastructure to Integrated urban Stormwater and Wastewater Management
    (AAU, 2017-06) Feyisa, Nibo; Agizew, Nigussie (PhD)
    The main goal of this study is to evaluate the existing urban wastewater and storm drainage management system and made recommendation on best selected alternative option of integrated urban wastewater and storm drainage management system. Any technical wastewater and stormwater management system adopted in urban drainage based on prior quantitate design discharge estimation. This study contributes a lot to understanding of the integrated urban water management system key technique to minimize the diffuse pollution load into natural stream, to reduce point source/wastewater discharges and to preserve the hydrologic regime of natural drainage systems. Wastewater and stormwater flow discharge are analyzed based on the three-part methodology. The rainfall of 100, 50, 25, 10, 5 and 2 year annual exceedance probability meteorological method was simulated SCS unit hydrograph rainfall-runoff using HEC-HMS. The calibration result indicates basin parameters were used in HEC-HMS model is improved. Different scenarios for landcover change were evaluated for all rainfall frequency models. The frequency storm of 25 year return period produced the maximum peak discharge at the outlet found 209m 3 /s in 1995, 238.1m 3 /s, in 2002 and 262.6m 3 /s in 2009. The hydrological response indicated that with urban area increase by 24.95%, an increase in peak flow. This study shows that peak discharge increase in 13.87% in period 2002, 25.64% in 2009 compared to period of 1995 as reference. The storm drainage management infrastructures are not updated – not sufficient to the peak discharge. Flooding impact on streets, and public property damage were reported in every year. The wastewater generation from domestic, industrial, public and intuitional have direct relation water supplied and 80% of water used is changed to wastewater. Monthly billed volume of consumed water from 2011 to 2016 was evaluated to determine domestic per capita demand. The average per capita demand is found 26.74l/cap/day. Per capita demand by mode of service were found 89.2L/cap/day for High Consumption, 41.48 L/cap/day medium consumption , 21.06 L/cap/day low consumption, and 9.88 L/cap/day very low consumption. From these demand estimation the total wastewater flow rate are found 2898.9m 3 /day (0.0334m 3 /s). Only 255m 3 /day (4%) of sewer facilities is existed for wastewater management system. These infrastructures are limited to only to onsite sewer line connected to the flash toilet, off-site pitlitrine discharged to treatment plant. GIS specific landscape Suitability assessed where specific practice to place, i.e. integrated urban water management system like stormwater best management practice and Wastewater Generation Reduction. The evaluated stormwater best management practices selected is Sediment Basins, Sand Filters Pervious landscape Pavements, Bio Basins, Infiltration, Ponds and Lakes, Swales & Buffer Strips, Bio Swales, Constructed Wetlands. For wastewater reduction the selected are Stormwater Harvesting/Reuse, Rainwater Tanks, Changing Landscape Form and Water Use Education Programs.
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    Evaluating the Impact of Land Use Change on Urban Drainage System and Proposed Low Impact Development measures in Addis Ababa, Ethiopia (Case Study of Megenagna - Bole Ring Road)
    (Addis Ababa University, 2020-09) Wondimu, Paulos; Agizew, Nigussie (PhD)
    Overflow of water from existing drainage is emerging issue in many cities of Ethiopia and mainly in Addis Ababa. Unplanned growth of urban areas is affecting the urban drainage system in Addis Ababa. The drainage networks in the city do not have sufficient capacity to carry excess runoff due to rapid expansion of built in environment. The roads turning into streams can be easily observed in all parts of the city, especially in Megenagna to Bole Ring Road, during rainy seasons. The purpose of this study was to estimate peak flow rate due to expanding built environment in the study area using SWMM and propose measures that reduce excess stormwater or excess runoff by using generic LID Controls. Stormwater Management Model (SWMM 5.1) was applied to simulate the urban runoff from the Bole Gerji delineated area (about 188 hectares) located in Addis Ababa, Ethiopia in conjunction with other software’s like ArcGIS, Google Erath Pro, Excel and so on to analyze the quantitative data. Model calibration and validation process was conducted by using daily observed and simulated runoff at selected outlet near Anbesa Garage. Model calibration and validation at selected outlet gives coefficient of determination (R2) and Nash-Sutcliffe simulation efficiency (NSE) values of 0.91 and 0.86 and 0.95 and 0.88 respectively. This result indicated good agreement between observed values simulated runoffs. Built up area coverage changes from 14% to 94% in the last 25 years, and no substantial rainfall intensity variation was observed. Runoff generated from all sub catchments changed from 4.27 m3/sec in the past (1995) to 12.94 m3/sec in the present (2019). Conduits C1, C2, C3, C4, C5, C6, C11, C12, C17, C18 and C24 were under surcharge situation and Nodes J3, J5, J17, J18 and J24 on the main road (Megenagna - Bole) were found to be flooding or overflowing with total volume of 11.4*106, 28.5*106, 7.6*106, 12.1*106, and 12.4*106 liters respectively. Evaluation of performances of the proposed low impact development measures indicated positive results. Changing 3.6 ha paved pedestrian by permeable pavement (Scenario 1) reduced total runoff by 12% and total node flooding by 11%; and changing 1.6 ha paved pedestrian by Bio – Retention Cells (Scenario 2) reduced total runoff by 5% and total node flooding by 4%. Based on the thesis result scenario 1 was recommended. Before, the urban drainage becomes a permanent socio-economic nuisance and brings irreversible damage to the city, this study strongly recommends immediate implementation of Low Impact Development Controls (LID) that are supported by strong institutional setup, policy framework, and the public at large.
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    Evaluation of Hydraulic Parameters in Old Akaki Well Fields
    (AAU, 2018-03) Yosef, Aregaw; Agizew, Nigussie (PhD)
    The primary objective of this study is analysis and evaluation of pumping test data to determine the aquifer hydraulic property of the Old Akaki bore holes by using Thies curve matching method; Cooper Jacob and Thies recovery method on excel sheet and aquifer test software. The proposed ground-water sources are from two main well-fields, Old Akaki and North Fanta, located at the suburb of Addis Ababa city. Old Akaki well field is located at about 22km South of Addis Ababa and East of Akaki Town. The abstracted water from Old Akaki well-field is able to serve various condominium sites in Kilinto & Koye Feche. In addition_ it serves other areas along the way & nearby the condominium sites in Akaki Sub City with additional supplies from North Fanta Well field. The transmissivity values obtained in this research has great variation from the study of WWDSE which accounts for 97 to 2000%. Among the eight wells analysed four wells have overestimated transmissivity, two wells underestimated and for two wells final result has not been obtained because of poor fitting of the Thies curve. The overestimated Transmissivity envisions good aquifer with better yield than the capacity of the aquifer. The underestimated Transmissivity values found to have lower yield than their discharging capacity. The well efficiencies were also computed for the expected yield (as suggested in the well completion report). The results clearly show that majority of the wells (five wells out of the eight tested wells) were found to work below the recommended operational efficiency. A well is considered acceptable if it works above 65% efficiency. Within tested wells only one well works in recommended efficiency range. Such a result clearly shows that the seven wells have already failed during design phase as they are expected to yield the values recommended in their well completion report. Such huge yield expectation from the wells will create a larger draw down in the well that the pump inside the well will no longer be sustainable. Therefore, in this evaluation it is recommended to conduct multiple well tests to determine the actual hydraulic parameters of the aquifer in order to obtain the safe yield of the wells which is intended to prolong the productivity of the aquifer and to delay excessive loss of saturated thickness.
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    Hydrological Modelling in Ungauged Catchment (In Case Suluh), Tigray
    (Addis Ababa University, 2017-09) Tewele, Gebretsadkan; Agizew, Nigussie (PhD)
    The study area of suluh catchment have the scarcity of record data, but the Suluh River have the capability of feeding the society nearby as source of small scale hydropower and irrigation. In addition to that since it is ungauged catchment it has no representing model of Rainfall- runoff relation and water harvesting structure. The work described here will attempt to solve these problems using the regional approach whereby statistically homogeneous regions are identified and the parameters of choosing distribution are estimated from the regional averages so that the flow quantile for the ungauged catchment within that region can easily be computed. So that the necessity of this study arises from the weight to improve site specific estimates based on limited data and to make inference about ungauged catchments. In ungauged catchments, model parameters have to be estimated from other sources of information. An appealing way to estimate model parameters in ungauged catchments is to glean the model parameters from hydrologically similar catchments. Hydrological modeling in ungauged catchments often involves the transfer of calibrated model parameters from donor (gauged) catchments to the receiver (ungauged). However, in any hydrological modeling, some parameters tend to be more sensitive to the objective function, whereas others are insensitive. Sensitivity analysis was performed to choose the most sensitive flow parameters that influence the catchment represented by SWAT to be used for calibration. This was achieved using the global sensitivity approach in semi-automated Sequential Uncertainty Fitting (SUFI2) algorithm. The global sensitivity analysis method takes into consideration, the sensitivity of one parameter relative to the other in order to give their statistical significances. The t-statistics and p-values of the parameters were used to rank to the different parameters considered to influence flow and the final selection done based on the significance of the ranked values. Table4 shows stream flow parameters that were tested for their sensitivity. These are useful in estimating the amount of flow from a catchment. The global sensitivity analysis of 21 flow parameters showed that, only eight were very sensitive to flow. Although, the rest of the parameters were found not to be sensitive to flow in the catchment as their p-values were greater than 5%. The Time period of 2000-2009 is used for SWAT model Calibration, and the 2009-2014 period for validation. Time series plots, as well as statistical measures, such as the coefficient of determination (R2) and the Nash-Sutcliffe efficiency (NS) parameter between observed and simulated stream flows are computed on monthly time scales and indicate a good performance of the final calibrated SWAT model. From the SWAT model output around 85% of the Suluh flow indicates surface runoff. The maximum rainfall of the catchment is about 331mm during a month of August and Similarly with surface runoff of 98.3mm.