Africa Center of Excellence for Water Management

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Evaluating the Land Use and Land Cover Change Impact on Streamflow Kulfo Catchment
(Addis Ababa University, 2021-09) Assebe Anja; Adane Abebe (PhD)
Stream flow is one of the major hydrological cycle components which can be altered and /or affected by different factors. From these, the Land Use Land Cover change is one of the main factors to alter and change the stream flow characteristics. Therefore, in this study, the LULC change impact on the stream flow was evaluated using the SWAT model for the case of Kulfo catchment which is situated in the Southern part of Ethiopia. Sensitivity, calibration, and validation were also conducted using sequential uncertainty fitting–version 2 (SUFI-2) in SWAT-CUP (Calibration and Uncertainty program) using historical streamflow data for each of the land use land cover years. Four different algorithms (SVM, CART, RF, and Navia's) which are existed in the Google Earth Engine were compared and the best performed was selected to generate the time-series LULC maps of, (1986, 2000, 2016, and 2020), the study area. The accuracy of these algorithms was evaluated corresponding to GCPs collected from the field. High resolution (30m) Landsat images which are thematic mapper (TM), Enhanced thematic mapper plus (ETM+), and Operational land imager (OLI) were used with the aid of historical trends and ground-based data used to train and validate the LULC maps generated from Google Earth Engine platform. As a result, the SVM algorithm was performed better in LULC classification than other algorithms which are compared in this study. In the analysis period of this study, the Vegetation land cover area has decreased from 18.81% to 3.1%, the agricultural land was increased from 19.44% to 57.12%, whereas the shrub land area has been decreased from 34.18% to 14.73%. Therefore, the effect of these LULC changes on stream flow was evaluated using Soil & water assessment tool (SWAT) model and high mean monthly and seasonal streamflow variability was observed in the analysis period of this study. These variabilities were increased from 6.72% to 7.85% monthly. In seasonal variability, the stream flow has decreased trend for all of the seasons (Kiremt, Belg, and Bega) from the year 2016 to 2020 whereas increased trend for the period of 2000 to 2016 (Kiremt, Belg and Bega). The Results from the calibration resulted in an acceptable range (0.6, 0.8, 0.75, and 0.75 for NSE and 0.75, 0.76, 0.79, and 0.81 for R2) between observed and simulated streamflow respectively. The results of validation were also fallen in the acceptable range (0.72, 0.6, 0.74, and 0.75 for NSE and 0.8, 0.75, 0.73, and 0.8 for R2) observed and simulated streamflow respectively.
De-Fluoridation of Ground Water Using Raw and Modified Bentonite Clay
(Addis Ababa University, 2022-06-12) Woldemedhin, Adane; Alemayehu, Esayas (Professor)
The presence of fluoride in groundwater sources of drinking water has posed a concern to global public health, particularly in the East African Rift Valley (EARV). The study's ultimate objective was twofold. First, investigate low-cost, locally available adsorbents for fluoride adsorption that could be used in Ethiopia's Rift Valley (which is the country's most fluorotic region), and second, contribute to the search for an appropriate and long-term fluoride removal technology for the treatment of fluoride-contaminated groundwater for drinking water for developing countries. Due to cultural beliefs and the terrible odor they emit, the use of bone char and the Nalgonda process for de-fluoridation is being rejected by users in the study area. Several researchers have advocated for the use of non–conventional low–cost adsorbents, such as natural materials and waste/byproducts from agriculture and industry, as effective adsorbents for the removal of fluoride from aqueous solution in recent years. Low–cost adsorbents, such as clay minerals, have emerged as a viable remediation technique for removing fluoride from polluted ground water. However, only a few clay minerals have been studied and investigated for their usefulness in removing fluoride from polluted water, either as is or after slight alteration. As a result, a new, cost-effective technology of fluoride removal is required. Therefore, in this study, the feasibility of fluoride adsorption from aqueous solutions using naturally available bentonite clay in both modified and unmodified forms is investigated. Scanning electron microscopy (SEM), energy dispersive X-ray (EDX), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy analysis was applied to describe the structure and nature of modified and unmodified bentonite clay. The physicochemical characteristics of the adsorbent were also investigated for moisture content, pH, apparent density, specific surface area, cation exchange capacity and its point-of-zero charge. Results obtained from these studies are presented and discussed. These effects of treatment or modification have been discovered. The EDX analysis reveals a significant silica and alumina content, as well as trace amounts of Fe+3, Ca+2, and Mg+2. The presence of the primary minerals, silica and alumina, with a minor amount of hematite, was revealed by XRD analysis. Furthermore, the silica and alumina levels have increased due to modification of the original material. SEM scans revealed considerable alterations in the original pore structure. The research involves a series of adsorption experiments in a column mode to evaluate the ability of the adsorbents for fluoride removal from polluted water. The column operations were used to investigate the practical application of the produced low–cost adsorbents for removal effectiveness at greater fluoride concentrations under an ideal pH setting of 7.2, which is suitable for drinking. Under the optimized values of the process parameters of initial fluoride concentration (mg/L), Flowrate (mL/min) and bed depth (cm) under continuously flowing fixed bed column was determined. At optimized conditions, RB have shown very low fluoride removal efficiency (47.19%), whereas, modification of the clay surface with HCl and aluminum oxide, on the other hand, increased fluoride removal efficiency to 79.77% and 94.38%, respectively for the 5mg/L of initial fluoride concentration, 10cm bed depth and 15mL/min flowrate. The statistical model, central composite design (CCD) and mathematical models were applied to evaluate the column adsorption performance. The adsorption modelling study reveals that for all models such as Thomas, Clarck, Yoon-nelson and Adam-Bohart, the lower the flow rates with higher bed height leads to maximum fluoride uptake on to adsorbent. The analysis of variance was used to determine the importance of independent variables and their interactions on adsorption capacity and Fluoride removal. All the R2 values indicate that the models match the experimental data well. Moreover, the study investigated the effects of co-existing ions in water on the performance of ALUM-MBENT, in column mode, the effects of anions on fluoride adsorption were investigated using concentrations of each anion of 0.1, 10, and 100 mg/L. When competing anions are present, the adsorption capacity of the adsorbent reduces, according to the findings. Multi-valent anions are more easily absorbed than monovalent anions. Carbonates and phosphate are the main anions that have the greatest influence on the fluoride adsorption. The fluoride adsorption is strongly affected by the concentrations of competing anions. Phosphate, bicarbonate, and sulfate greatly reduced fluoride adsorption. However, chloride had little effect on the sorption. The impact of major anions on fluoride adsorption followed the order of Cl-
Evaluation of Roof Tops Rainwater Potential for Alternative Water Supply Source a Case of Wachemo University Main Campus
(Addis Ababa University, 2021-09-25) Abreham, Tamirat; Tesseme, Tamru (PhD); Mulugeta, Eyobel (PhD)
Roofs top rainwater harvesting has been carried out worldwide to afford an alternative source of water for many people. The aim of the present study was to evaluate of the rooftop rainwater harvesting potential for alternative supply source in Wachemo University. A 20-years rainfall data was analyzed to determine the average monthly and annual rainfall potential in the study area. The possible volume potential that can be harvested from the selected rooftops of the Wachemo University was quantified using rational method. Ripple mass curve method was also applied to determine the storage capacity of the water tank for the harvestable rooftop rainwater in the study area. Google earth and ArcGIS 10.3 tools were used to digitize the buildings rooftops and to locate water sample points. The quality of the rooftop rainwater was examined as per the standard method for the examination of water and wastewater quality. Considering only the four wet season months (March through October), the monthly variation with coefficient of variation ranges between 33% and 69% and yearly variation between 13% and 24 % .The maximum potential of rainwater with annual average rainfall amount 1188 mm and rooftops area 107587 m2 was found to be 102,268 m3 /y which can be harvested from roofs provided that all rain falling on the roofs is collected. This is equivalent to 52.4 % of average water demand of the community in the university. The Ripple mass curve method showed that about 4269.2m3 of storage tank capacity is essential to store the harvestable rooftop rainwater. The water quality examination revealed that of the qualities of the rooftop rainwater were found within the permissible limit of drinking water quality as per the WHO (2017) guideline except the values of the bacteriological parameters. Total cost for installing the rainwater harvesting system in 94 similar buildings inside the Wachemo University main campus evaluated as 6,937,200 Et.Birr (149,187 USD). The study concluded that rooftop rainwater harvesting is a promising alternative solution in Wachemo University to solve water scarcity problem and for ensuring a continual source of non-potable water.
Assessment of Water Loss and Performance Evaluation of Distribution System (the Case Ofhosanna Town SNNPR Ethiopia)
(Addis Ababa University, 2021-07-02) Wamolo, Mohammed; Kebede, Andinet (PhD)
One of the biggest difficulties facing Ethiopia's urban water utilities is the reduction of excessive water losses. Water supply inconsistency and imbalanced distribution in Hosanna town is a major issue for the town's people. Despite the fact that the town has more than six sources of drinking water, considerable losses in the distribution system, along with an alarming increase in urbanization, have a significant impact on the supply shortfall. The major goal of this research was to determine the level of water supply coverage and distribution system losses. The hydraulic performance of the water supply distribution system was assessed using WaterGEMS. The existing distribution layout, Hosanna town administration master plan, and geospatial data were used as input data for WaterGEMS. The free water audit software from the American Water Works Association was used to assess the water loss. Financial and operational performance metrics, as well as the infrastructure leakage index, were used to assess total water losses and non-revenue water. The volume and cost of water lost and non-revenue water are reported in terms of volume and cost. The town's water supply covers 60% of the population, and the average daily per capita use is 29.02 liter. The data demonstrate that the GTP-2 aim of water supply coverage was not met. Water was lost from the system at a rate of 29.48 percent of total input water, including both apparent and real losses. The financial performance indicator for non-revenue water was found to be 30.73 percent of total generated water, including unauthorized use, apparent losses, and real losses. The infrastructure leakage index, which measures the efficiency of the distribution system, is 2.50. The hydraulic model was calibrated using observed pressure data as well, and the resulting coefficient of determination (R2) was 0.997. According to the findings, the performance of Hosanna town's water supply distribution system is quite poor.
Assessment of Municipal Solid Waste Generation Composition and Effects of Dumping Site on Water Quality at Mizan-Aman Town
(Addis Ababa University, 2021-03-02) Barnabas, Gera; Mekonnen, Andualem (PhD)
In Ethiopia, despite the progress that has been made to advance water supply access and the health status of the population in the last one and half decades, communicable diseases account for about 60-80% of the health problems. The existing burden of diseases is preventable and a considerable proportion is directly related to using unsafe water. Poor solid waste management systems from urban municipal dumpsites into surface and groundwater sources can be harmful to the urban population who use these water sources. Gradual accumulations of contaminants in the water sources can result in high loads of pollutants that are potentially toxic to the users. In Mizan Aman Town River Gechab, Cosakol, Shonga, Petrous, and Nimbus drain through the town and improved groundwater wells are the main sources of potable water for most residents. This study was conducted from December 2020 to April 2021, intending Assessment of Municipal Solid Waste Generation, Composition and Effects of Dumping Site on Water Quality at Mizan-Aman Town Bench Maji zone, SNNPR, Ethiopia A random research design was used in the study. The solid waste generation rate, composition, and disposal practices were assessed. The water quality of water resources around dumping sites was assessed. Water samples were collected from wells and the surface water during both the dry and the rainy seasons. The results that were found in the research were used as baseline information for a government institution to provide methods of managing solid waste disposal systems and to plan efficient collection and management of solid waste from the source of generation to disposal site. The Physic-chemical parameters measured show that other than the pH, total hardness, electrical conductivity, TDS, iron, fluoride odor, and taste, all other concentration values exceeded the Ethiopia minister of water and irrigation guidelines for drinking water and WHO guideline. The presence of a high load of bacteria in both surface and groundwater samples means that leachate is altering the water quality of water in the vicinity of the dumpsite. The bacteriological concentration of water from all sampling sites exceeded the Ethiopian minister of water and irrigation standards. Hence the surface and sub-surface water in the neighborhood of the dumpsite presents a significant threat to public health.
Determination of Heavy Metal Concentration and Physico-Chemical Properties of Selected Paint Factories Effluents and their Impact on the Germination and Growths of Vegetables
(Addis Ababa University, 2021-09-02) Rebuma, Mekwanint; Chebude, Yonas (PhD)
Effluents from the paint industry have been a major source of environmental pollution. The paint industry generate wastewater, primarily due to cleaning operations of mixers, reactors, blenders, packing machines and floors. There is a need to investigate the compliance of wastewater discharged from paint industries with regulatory standards. In response, this study evaluates the physicochemical parameters of both raw and treated wastewater, the wastewater treatment plants (WWTPs) efficiencies as well as the compliance level of three selected paint manufacturing companies in Addis Ababa, Ethiopia, with some regulatory standards: Ethiopian Standard and World Health Organization (WHO). A study on the impact of a paint industry effluents on the vegetables solanum lycopersicum (tomato) and D. carota (carrot) was also carried out. Analysis of physico-chemical and heavy metal parameters of selected paint factories’ samples in Kadisco (CA), Zemilli (ZE), and Nifas Silk (NS) were performed to investigate the concentration of status of the parameter. In this study, physicochemical and heavy metal parameters such as pH, TDS, EC,COD, BOD, PO43-, NO3-, SO42+, NH3, NH4+, Cr+6,Zn+2, Cd and Pb of the fourteen wastewater samples were analyzed using, standard methods. The values of pH, electrical conductivity (EC) and total dissolved solids (TDS) levels were in the range of 6.80-8.50, 858.00 - 2540.00 mS/m and 410.00- 1270.00 mg/L, respectively. The range of other parameters include ammonia; 0.35-0.42mg/l, biological oxygen demand (BOD); 6.40 – 35.76mg/L, chemical oxygen demand (COD); 283.00–485.0 mg/L, nitrates; 0.68-12.50 mg/L, phosphate; 1.31-1.52, sulfate; 32.33–188.33 mg/L, lead; 0.01–0.06 mg/L, zinc 0.01-0.02 mg/L while cadmium and chromium were below detection limits. The results indicated that the WWTPs of the studied paint factories were ineffective in reducing the pH, TDS, and EC to acceptable limits. Wastewater samples were collected from two paint factories (Kadisco paint and Nifas Silk paint factory) and their impacts on the germination and growth of (vegetables solanum lycopersicum (tomato) and D. carota (carrot)) have been studied. The obtained results revealed that wastewater from Cadisco paint factory did not affect seed germination except a minor inhibition in solanum lycopersicum (tomato). Effluents from Nifas Silk factory stimulated seed germination in both solanum lycopersicum (tomato) and D. carota (carrot). It can be concluded that paint factories wastewater may have different effects on growth of different vegetables, depending up on the nature of wastewater and sensitivity of a plant species to wastewater.
Effectiveness of Uv-Disinfection Against Cercaria at Selected Wavelegnth Using Uv-Leds (for Schistosomiasis Control)
(Addis Ababa University, 2021-06-14) Eritrea, Eden; Zewge, Feleke (PhD); Templeton, Michael (Professor)
Due to a lack of water and sanitation, schistosomiasis is a neglected tropical water-based chronic illness that kills. It is spread to people through contact with cercariae-infected water on the skin while bathing, swimming, or in any other way. In earlier research, various studies, including UV irradiation, have been conducted to eradicate the diseases-causing pathogenic parasite known as cerceriae. However no studies were carried out using the newly emerging UV-technology such as UV-LEDs. Hence the objective of this study was to investigate the effectiveness of UVC-LEDs (with a wavelength of 255nm, 265nm and 285nm) to disinfect Schsitosoma cercariae. Snails which an intermediate host for Schsitosoma cercariae were collected from Hawassa (Tikur Wiha River) and also from Lake Ziway. The collected snails were prepared for shading cercariae and 100-120 cercariea were prepare in 200μL. The disinfection of cercarea was examined using UVC-LEDs at a wavelength of 255 nm, 265 nm and 285 nm respectively. Using fluence (UV-dose) of 1 mJ/ cm2, 20 mJ/ cm2 ,40 mJ/ cm2, 60 mJ/ cm2, 80 mJ/ cm2, 100 mJ/ cm2, 120 mJ/ cm2,160 mJ/ cm2, 200 mJ/ cm2 and 300 mJ/ cm2. Under controlled settings, the experiment was repeated three times in a solution containing 200μL of cercariae-infested water and 3.6 ml of bottled water.All fluence (UV-dose) showed no significance cercariae disinfection at a wavelength of 255 nm. But Wavelengths 265 nm and 285 nm showed significance cercariae disinfection. 1 log reduction was achieved at a fluence of 300 mJ/ cm2 and wavelength of 265nm and 1.5 and 2 log reduction was achieved at fluence of 200 mJ/ cm2 and 300 mJ/ cm2 at wavelength of 285nm. It took 300 mJ/ cm2 fluence (UV-dose) to achieve 2 log reduction which is high compared to fluence used in different studies to disinfect other pathogenic parasite. Therefore, in this study UVC-LEDs used is a promising technology to disinfect schsitosoma cercariae but requires further studies. Therefore, more research and different methodology is needed to enhance its use and effectiveness.
Performance Assessment of Wastewater Treatment Plant in Ethio-leather Factory using GPS-X Wastewater Modeling and Simulation Software
(Addis Ababa University, 2021-11-17) Agiza, Kibrework; Kebede, Shimelis (PhD)
Ethio-leather industry (ELICo) is one of the most important factories in Ethiopia, located in Addis Ababa’s Akaki Kality sub-city, with an annual capacity of 6600 tons. The company generates a maximum of 1200 m3/day of wastewater effluent. Company uses raw water at a rate of 2000 m3/day on average, equivalent to 90 m3 of water per ton of finished leather goods. This research investigated the efficiency of the tannery wastewater treatment plant for water recycles as a substitute for groundwater. It has also evaluated the performance of the wastewater treatment plant using Hydromantis GPS-X, a commercially available wastewater treatment plant modeling and simulation software tool. For this task Physicochemical laboratory analysis, field measurement and secondary data, were used to acquire the input data for process modeling and simulation. It tested all parameters using the Water and Wastewater Standard Method from the Physico-chemical analysis of the wastewater generated from the plant. This paper understands, effluent water quality found below the standard discharge limit by Ethiopian Environment, Forest and Climate change Commission. According to physico chemical characteristics treatment plant has 93.6% of COD, 97.44% of BOD5 and TSS of 98.8% removal efficiency this is some of conducted parameters. In this research, the GPS-X model was run after a sensitivity analysis calibration and validation phase. According to the result of the steady-state and time dynamic sensitivity analysis, the model was sensitive to changes in input and good enough to be used as a parameter prediction. This research successfully validated the developed model while meeting the assumption of the models’ constant stoichiometry and kinetic coefficients for any plant influent characteristics. Model validation also shows that it is 76.11 percent accuracy in predicting plant performance and the simulation result shows a satisfactory effluent water quality parameter. Therefore, this research discovered that it can be recycle in some parts of the tannery process. The findings of the physicochemical characterization and process simulation evaluation substantiated this.
The Impact of Hydrological Parameters and Climate Inputs on Extreme Streamflow Simulation in Upper Awash River Basin
(Addis Ababa University, 2021-06-08) Mezgebu, Metsihet; Kidane, Hadush (PhD)
Quantifying possible sources of uncertainty in simulations of hydrological extreme events is very important for better risk management in extreme situations and water resource planning. The main objective of this research work is to identify and address the role of input data quality and hydrological parameter sets, and uncertainty propagation in hydrological extremes estimation. This includes identifying and estimating their contribution to flood and low flow magnitude using two objective functions Nash-Sutcliffe efficiency for flood and Log Nash-Sutcliffe efficiency for low flow, 20, 000 Hydrological ByransVattenBalansa Vdelning hydrological parameter sets, and three frequency distribution models (Log-Normal, Pearson-III, and Generalized Extreme Value). The influence of uncertainty on the simulated flow is not uniform across all the selected three catchments due to different flow regimes and runoff generation mechanisms. The result shows that the uncertainty in high flow frequency modeling mainly comes from the input data quality. In the modeling of low flow frequency, the main contributor to the total uncertainty is model parameterization. The total uncertainty of QT90 (extreme peak flow quintile at 90-year return period) quintile shows that the interaction of input data and hydrological parameter sets has a significant role in the total uncertainty. In contrast, in the QT10 (extreme low flow quintile at 10-year return period) estimation, the input data quality and hydrological parameters significantly impact the total uncertainty. This implies that the main factors and their interactions may cause considerable risk in water resources management and flood and drought risk management. Therefore, neglecting these factors and their interaction in disaster risk management, water resource planning, and evaluation of environmental impact assessment is not feasible and may lead to big risk.
Evaluating the Land Use and Land Cover Change Impact on Streamflow Kulfo Catchment
(Addis Ababa University, 2021-10-27) Anja, Assebe; Abebe, Adane (PhD)
Streamflow is one of the key components of the hydrological cycle that can be altered and/or modified by a variety of variables. One of the key variables is the change in LULC. In kulfo cathement, in Ethiopia's southern region, suitable LULC detection techniques were not addressed and evaluated yet, and also the changing of the exesting LULC is the main stress in the streamflow of the Kulfo catchment. As a result, the impact of LULC change on streamflow was assessed in this study using the soil and water assessment tool model. Sensitivity, calibration, and validation were also performed using historical streamflow data in SWAT-CUP (Calibration and Uncertainty program) using sequential uncertainty fitting–version 2 (SUFI-2). There were four different algorithms applied to classify the LULC change. The best performing of four distinct algorithms (SVM, CART, RF, and Navia's) available in the Google Earth Engine were compared, and the best performing was chosen to generate the time-series LULC maps of the research area (1986, 2000, 2016, and 2020). GCPs gathered in the field were used to assess the accuracy of these algorithms. To train and evaluate the LULC maps generated from the Google Earth Engine platform, high resolution (30m) Landsat imagery from the thematic mapper (TM), enhanced thematic mapper plus (ETM+), and operational land imager (OLI) were employed, along with historical trends and ground-based data. As a result, the SVM method outperformed the other algorithms in this study when it came to LULC classification. During the study's period, the area covered by vegetation declined from 18.81 % to 3.1 %, while agricultural land increased from 19.44 % to 57.12 % and shrub land decreased from 34.18 % to 14.73 %. As a result, the impact of these LULC variations on streamflow was assessed using the Soil & Water Assessment Tool (SWAT) model, and over the study's period, substantial mean monthly and seasonal streamflow variability was observed. Monthly, these variabilities were raised from 6.72 % to 7.85%. The year has been divided in to three seasons Kiremt, Belg, and Bega. Seasonally, streamflow has dropped for all seasons (Kiremt, Belg, and Bega) from 2016 to 2020, but it has increased from 2000 to 2016. (Kiremt, Belg, and Bega). The calibration results showed an acceptable range between observed and simulated streamflow (0.6, 0.8, 0.75, and 0.75 for NSE and 0.75, 0.76, 0.79, and 0.81 for R2). Validation findings for observed and simulated streamflow were similarly within acceptable limits (0.72, 0.6, 0.74, and 0.75 for NSE and 0.8, 0.75, 0.73, and 0.8 for R2).
Hydrological and Hydrodynamic Modelling of Flows to Support Establishment of Flood Adaptation Strategies for River Malaba Sub-Catchment in Uganda
(Addis Ababa University, 2022-03-22) Mubialiwo, Ambrose; Abebe, Adane (PhD); Onyutha, Charles (PhD)
Many people tend to live in the floodplains along River Malaba due to fertile soils which support agriculture. However, heavy rains in the highlands of Mount Elgon often lead to floods which end up affecting especially the local population in terms of loss of lives and destruction of infrastructure within the low-lying areas of River Malaba sub-catchment in Uganda. This research aimed at presenting a platform for understanding the impacts of flooding on the socio-economy while investigating perceived effectiveness of establishing flood adaptation strategies for predictive risk-based water resources management in the study area. The study had four specific objectives including; (i) to analyse changes in historical rainfall and potential evapotranspiration (PET), (ii) to perform hydrological modelling of extreme peak flows, (iii) to estimate impacts of flooding given the spatial extents of flooding inundations, and (iv) to analyse community willingness-to-pay (WTP) for flooding adaptation strategies. Changes in terms of trends and variability were analysed using nonparametric approach based on the cumulative sum of the difference between exceedance and nonexceedance counts of data points. The second specific objective consisted of determining which hydrological model could best reproduce observed extreme peak flows. Hydrodynamic modelling was performed using a two-dimensional Hydraulic Engineering Center’s River Analysis System model. Double-bound dichotomous choice contingent valuation method was applied to assess the local population’s WTP for flooding adaptation measures. The number of days with rainfall intensity > 5 mm/day and 10 mm/day had insignificant (p>0.05) decreasing trend. The sum of rainfall with intensities > 5 mm/day exhibited a significant (p<0.05) decreasing trend. However, annual maxima rainfall increased (p>0.05), indicating less frequent rains but some events having very high intensity. Variability of rainfall sub-trends was insignificant (p>0.05) and had a common pattern. PET had an insignificant (p>0.05) positive trend. The amplitudes in PET variability were insignificant (p>0.05) and though of generally common pattern. The Australian Water Balance Model exhibited the best performance in reproducing extreme peak flows and it had Nash–Sutcliffe efficiency (NSE) of 0.837. Land-use change had insignificant (p>0.05) influence on determining flood inundation extents. Inundation of rice gardens by the most severe 100-year flood was found to lead to an economic loss of about US$ 39 million. Amongst the infrastructure, churches showed the highest economic losses of US$ 1,623,832 due to flooding of 100-year return period. In general, the local community was aware of the flood citing rainfall variability and longer rainfall durations as main cause of flooding. Post- flood strategies were more efficient than those practiced before- and during-floods. Among the suggested structural and non-structural strategies, “river training structures” and “flood forecasting and early warning” were highly preferred, respectively. 55% of the households expressed WTP an individual amount between Uganda shillings (UGX) 5,000 (US$ 1.35) to UGX 500,000 (US$ 135.14). Several demographic, social and institutional factors had significant (p<0.01) positive impact on community WTP. This study findings are relevant in supporting policy makers regarding predictive planning and development of flood risk adaptation pathways given the established destructions within the sub-catchment due to flooding.
Watershed Regionalization for Regional Flood Frequency Analysis in the Rift Valley Lake Basin Ethiopia
(Addis Ababa University, 2021-03-17) Sime, Abdisa; Abebe, Adane (PhD)
The use of regional information to predict magnitude of flow both at site and ungauged catchments are useful for planning and management of water resources. The main objective of this study was to regionalize watersheds in the Rift Valley Lake Basin (RVLB) and flood frequency analysis for the delineated homogeneous regions. In regionalization of the watersheds; Physiographic, drainage, meteorological, soil cover, land-use pattern characteristics and geographical location attributes have been used. Cluster analysis was done by Hierarchical clustering to obtain number of clusters, and final clustering by K-mean method. Accordingly four regions have been identified and checked using homogeneity tests. Using goodness of fit tests (Chi-square test, Kolmogorov–Smirnov, and Anderson–Darling), the best fit distribution models have been selected. Generalized extreme value distribution is the best fit for region I, Log-normal (2P) is selected for region II, Wakeby distribution is found to be the best for region III, and Generalized pareto is chosen for region IV. For the selected distributions efficient parameter estimation technique was selected by performing standard error analysis. Thus, method of moment (MOM) is the one with the lowest error so, selected for region I, and maximum likelihood (ML) method is found the most efficient method for the regions II to IV. For each region unique regional frequency curve is developed with standardized annual maximum flow series (AM), which is a crucial to estimate flood quantile in ungauged areas of the basin. Regional regression model was developed for all region except for region I which consists only one gauged catchment based on their R2 values. Accordingly 0.82, 0.83, and 0.79 of R2 values respectively for all the three regions. For checking performance of the model, validation of regional model was carried out by computing the relative errors, over five gauged watersheds that is representative for each region considering as pseudo ungauged. The relative errors between observed and estimated mean annual maximum flows resulted all regional model performs good having maximum of 10.6% of relative error. So, for any current and future water resources developments in the area, the developed regional model can be applied.
Sustainability Assessment of Urban Water Distribution System a Case of Bahir Dar City Ethiopia
(Addis Ababa University, 2021-10-11) Antehun, Yirged; Alemayehu, Esayas (Professor); Mekonnen, Andualem (PhD)
One of the most fundamental requirements of human life is water. As a result, everybody should have access to adequate and safe water on a continuous basis. For adequate and safe water supply, proper design and execution of the new distribution and the operation of the existing distribution network is needed. The study aimed to assess the sustainability of Bahir Dar City's pressure zone-1 water supply distribution system. For assessing the hydraulic sustainability, an analytical model (WaterGEMS V8i) was used to model the WDN and produce hydraulic parameters (velocity and pressure). Sustainability indicators (reliability, resilience, and vulnerability) were calculated based on these parameters and used to determine the sustainability index. The WaternetGEN tool was used to assess the distribution network's hydraulic performance. A geographic positioning system (GPS) and Arc GIS 10.4.1 was used to check the existing layout and to generate the study area. The results showed that; the distribution system has overall sustainability indexes of 0.71 for the current peak hour demand, with sustainability indexes of 0.97 and 0.43 for pressure and velocity, respectively. Based on the result of this analysis the distribution network sustainability is acceptable for current demand. However, the overall sustainable indexes for forecasted demand has been reduced to 0.32, which is in the medium range but unacceptable. It is found that also Pressure in a WDN had a technical performance index of 86.53 %, while the performance indexes of velocity in the distribution system is 57.86% after optimization of the hydraulic parameters in WDN. Water age was determined at low demand hour. Analysis for water age was based on assumption that the distribution system was loaded with continuous flow. The maximum water age in the distribution system is 19.93 hour which is less than a day and acceptable. In general, the result of this study showed that the current distribution network is sustainable for the current water demand.
Peak Flow Projections Under the Influence of Climate Change Impact and Uncertainty Evaluation in the Upper Awash River Basin Ethiopia
(Addis Ababa University, 2021-09-17) Berhane, Tarikua; Kidane, Hadush (PhD)
Modelling climate change impact on peak flood is subject to considerable uncertainty that comes from the climate model discrepancies, climate bias correction methods, and hydrological model parameters. These factors play a crucial role in flood risk planning and extreme event management. With the advent of the Coupled Model Inter comparison Project Phase 6 (CMIP6), flood managers and water resource planners are interested to know changes in catchment flood risk are expected to alter relative to previous assessments. A catchment-based projected change in peak flood quantiles for Upper Awash catchment was quantified. Conceptual hydrological model, three downscaling techniques, and an ensemble of hydrological parameter sets were used to examine changes in peak flood quantile magnitude and frequency under climate change in the mid and end of the 21st century. The results show that projected annual extreme precipitation and peak flood quantiles could increase substantially in the coming decades by 30%-55% in all the selected catchments. The associated uncertainty in future peak flood quantiles was quantified using aggregated variance decomposition and the result confirms that climate change is the dominant factor in Akaki (55%) and Awash H (51%) catchments, whereas the bias correction approaches in Awash B (58%) and Kela (50%) catchments. In Awash catchment both climate models and bias correction methods (45% and 49%, respectively) are the most dominate factors in projected peak flood magnitude. The hydrological parameter sets are identified as least important factor in the flood projections. Moreover, these results may add some significant information in the range of plausible changes expected for policy-relevant flood indices, and the tailoring of adaptation plans to account for the new generation climate model outputs.
Analysis of Hydraulic Performance and Water Loss Status using Water Balance Software in the Water Supply Distribution System of Yeka Abado Condominium in Addis Ababa
(Addis Ababa University, 2021-10-13) Dejene, Emebet; Kebede, Andinet
Water is a valuable resource that must be managed holistically in order to avoid scarcity. This study was carried out as part of the management to analyze hydraulic performance and water loss status in the water supply distribution system of Yeka Abado Condominium in Addis Ababa using water balancing software. To analyze water loss components and evaluate the system's performance, water balancing software was employed. The condominium's present water supply coverage was assessed using statistical analysis, and the hydraulic performance of the water distribution system was assessed using WaterGEMS V8i software. It was also used to add pressure-reducing valves to the system and assess the pressure reduction after they were installed. The average daily per capita water consumption and level of connection per family, according to the analysis, were 65 l/p/d and 17.3 percent, respectively. This demonstrates a lack of water supply coverage for condominium residents, which is mostly impacted by water scarcity. The findings of the water loss analysis, on the other hand, revealed that the overall water loss in the study area water supply system was 24.6 percent of the system input volume, with 96 percent of this being true loss and only 4% being apparent loss. The results revealed that the water loss value was modest, indicating that the system is in good working order. The WaterGEMS model, on the other hand, found that a number of junctions had pressures exceeding the maximum permissible pressure of 60 m. Pressure lowered valves were installed in the system to solve the high-pressure problem and reduce pipe leakage, and the changed pressures were within the standard's optimum level. As a result, maintaining appropriate pressure in the system to meet customer demands is necessary, as is restricting the optimal values to prevent leakage flow rate and the risk of pipe burst or fracture.
Assessment of Effluent Characteristics and Wastewater Management Practices in Selected Hospitals of Addis Ababa Ethiopia
(Addis Ababa University, 2021-09-11) Bekele, Biniyam; Tekola, Beteley (PhD)
Pollutants from hospital wastewaters are becoming serious issue in both developing countries of the world. There is a need to evaluate the quality of wastewater discharged from hospitals with regulatory standards. In response, this study investigates the wastewater generation, characteristics and sewage management practices in seventeen selected hospitals in Addis Ababa, Ethiopia. Descriptive study was employed to understand the status of wastewater management practices. Wastewater sampled weekly from August 10/2020 to August 24/2020. Two public hospitals were used to analysis of heavy metals, bacteriological and other physico-chemical wastewater parameters were analyzed using standard methods and the results were compared with effluent permissible limit standard of the City (AACGEPGD). pH, Conductivity, Turbidity and Total coliform levels were in the range of 6.8-7, 1058-1390 μS/cm, 60-152 NTU and >2400 MPN, respectively. The range of other parameters include total suspended solids; 100-550 mg/L, total solids; 692-1528 mg/L, total dissolved solids; 410-1428 mg/L, chemical oxygen demand; 93-443 mg/L, biological oxygen demand; 29-118 mg/L, total organic carbon; 2-9 mg/L, total nitrogen; 1-18 mg/L, total phosphate; 13-40 mg/L and sulfate; 16-48 mg/L, mercury; 0.003-0.21 mg/L, manganese; 0.05-0.93 mg/L, zinc; 0.02-0.85 mg/L and iron; 0.7-4.89 mg/L, were investigated. The results indicated that the effluent quality of the presented hospitals for most wastewater parameters such as; EC, TSS, TDS, BOD5, COD, TP, TN and Total coliforms were above the standard permissible limit of the city (AACGEPGD). Therefore, the surveyed hospitals must need to adopt preferable wastewater treatment plant up to the existing standards.
Determination of 2,4-Dichlorophenoxyacetic Acid in Water Sediment and Soil Using High Performance Liquid Chromatography
(Addis Ababa University, 2021-07-09) James, Stella; Ele, Estifanos (PhD)
2,4-Dichlorophenoxyacetic acid (2,4-D) is a widely used herbicide throughout the world to control broad-leaved herbs in various crops. Despite widespread use in a number of countries, studies have revealed that 2,4-D is a possible carcinogen and has a number of neurotoxic effects. The purpose of this study was to develop a method for extracting and determining 2,4-D acid from the soil, sediment, and water, as well as to investigate the compound's stability in water. The analysis was performed using high-performance liquid chromatography with UV detection at 230 nm. The performance of the developed analytical method was evaluated by extracting the analyte from spiked soil and water samples; recoveries ranged from 88 to 100%. A calibration curve for the method using known concentrations of 1, 10, 20, 40, 60, 80, and 100 mg/L of the analyte showed good linearity (R2 ≥ 0.9996). The LOD of the developed method was determined to be 0.45 μg/mL while the LOQ was 2 μg/mL. From the analysis of the samples, no 2,4-D was detected in sediment or soil samples from the Wafiko or Kontola sites, respectively. 2,4-D concentrations in soil samples from Bochessa and water samples from Wafiko and Sher site were generally high and exceeded USEPA regulatory agency standards. On the nature of the compound in water, a 45-day experiment on spiked water samples from Lake Koka demonstrated that the acidic form of 2,4-D is stable in water. An average recovery 73.46 ± 2.00% was achieved in this study. Thus, this study suggests that the developed method can be used to quantitatively extract 2,4-D residues and other chemical pollutants with similar physicochemical properties from contaminated samples originating from various sources.
Recovery and Removal of Phosphorus via Struvite (MgNH4PO4. 6H2O) Crystallization in Fluidized Bed Reactor from Domestic Wastewater
(Addis Ababa University, 2021-09-20) Tamru, Eskinder; Kebede, Shimelis (PhD); Feleke, Adey (PhD)
Phosphorus is a vital nutrient for food production which is produced from limited, non-renewable resource called phosphate fossil. At the present rate of utilization, the world’s reserve of phosphate fossil will be exhausted soon. However, wastewater contain huge amount of phosphorus which can be recycled to reduce depletion of phosphate fossil. Beside this fact, phosphorus should be removed from wastewater before discharging it into water bodies, to avoid eutrophication. One of the promising methods of phosphorus recovery in to useful end product is struvite crystallization. The present study focuses on recovery of phosphorus via struvite crystallization from domestic wastewater in fluidized bed reactor. Response surface experimental design was implemented to optimize process parameters such as pH (8 – 12), ammonium to phosphate molar ratio (1 - 4), magnesium to phosphate molar ratio (0.5 – 2.5) and reaction time (1hr. – 5 hr.) using model solution. The optimized value for pH, ammonium to phosphate molar ratio, magnesium to phosphate molar ratio and reaction time were found to be 10, 2.9, 1 and 4 hr. respectively. Under this optimized value 81% and 74% phosphorus removal efficiency was achieved from model solution and domestic wastewater respectively. Similarly, 1.29 and 2.9 gram of struvite yield was obtained from 10 litter of model solution and domestic wastewater respectively. Although higher amount of struvite yield (2.9 gram) was obtained from domestic wastewater, struvite crystal purity was lower (68.7%). Elemental composition of crystals precipitated under optimized condition indicate that octahedral struvite crystals was the dominant compound which was further identified by scanning electron microscope, Fourier transform infrared spectroscopy and X-ray diffraction. This study also investigated the potential of Basaka Lake water as locally available magnesium source for struvite crystallization. Seventy nine percent (79%) and sixty eight percent (68%) phosphate removal efficiency were achieved from model solution and domestic wastewater respectively by employing Basaka Lake water as a source of magnesium. Overall, struvite crystallization from domestic wastewater is a sustainable eco-friendly approach for removal of phosphorus via struvite which can be used as fertilizer in agricultural sector.
Evaluating the Effect of DEM and Boundary Condition Data for Hydrodynamic Flood Modeling in a Data Scarce Area Akaki Catchment
(Addis Ababa University, 2021-07-08) Negussie, Abel; Tamiru, Alemseged (PhD)
Accurate flood inundations mapping is challenged by data availability for model calibration and validation. In this regard, evaluating the effect of input data for improving flood inundation mapping is necessary. In this study, a high-resolution digital elevation model (DEM) of 5m × 5m was obtained from the Ethiopia Geospatial information institute. However, the high-resolution DEM (5m) was found to have some limitations in capturing the river channel geometry of Akaki. As a result, field-measured (fifteen cross-sections) data was merged with DEM to improve the accuracy of the DEM. To fill the gap of boundary condition data, water depths of a flood event were measured at upstream (for simulating the model) and middle (for evaluated simulated water levels) parts of the model domain. For the tributary river, a stage hydrograph was developed based on community consultation and channel characteristics. HEC-RAS was used in this study to perform one-dimensional (1D) flood modeling of the Akaki floodplain and HEC-GeoRAS 10.4 was used for the processing of geospatial data and analysis of water surface profile results. The limitation of the DEM to capture the channel geometry was significantly improved by using field-collected cross-sections. The type of downstream boundary condition is found significant error source in modeling the flood of Akaki. Error statistics for model simulations show that the mean absolute error of water level is 1.65m when using the uncorrected DEM as model input. However, this was reduced by half as a result of correcting the DEM. The model results show that the two tributaries have a large contribution to the flood inundation of the study area. Overall, this study demonstrates how input data source and associated errors significantly affect the accuracy of flood characteristics that are simulated by a hydrodynamic flood model. As a result, researchers and concerned institutions should develop strategies to develop data gaps for enhanced understanding of flood hazard in the Akaki catchment.
Synthesis and Characterization of Graphitic Carbon Nitride for the Removal of Methylene Blue Dye from Wastewater
(Addis Ababa University, 2021-10-30) Ayalkibet, Eyerusalem; Kebede, Shimelis (PhD)
Graphitic carbon nitride (g-C3N4) has received much attention for its potential application in pollutant degradation due to its unique optical and physicochemical properties. Various technologies have been developed to remove pollutants, but efficient and economical wastewater treatment remains a challenge in terms of energy and treatment costs. Herein, a visible-light active and robust semiconductor, g-C3N4 was synthesized from low-cost precursors like urea using pyrolysis at 500 ºC and 550 ºC. Herein, the as-synthesized material was characterized by UV-vis spectrophotometer to show the catalyst optical characteristics and can consider the best reaction temperature to obtain graphitic carbon nitride with maximum visible light response. Likewise, Fourier transform infrared spectroscopic (FT-IR) analysis was required to confirm the structure and the presence of C=N or functional groups. Sample morphology and structure were characterized by scanning electron microscopy (SEM), nitrogen adsorption-desorption isotherm analysis, X-ray diffraction (XRD). In this research important photocatalytic degradation procedure, the factors that affect the efficiency of photocatalytic degradation of organic pollutants, and the effects of different reaction parameters are highlighted. The photo-catalytic degradation of methylene blue (MB) was evaluated under visible light irradiation. As prepared sample having a specific surface area of 54.9 m2/g, the photo-catalytic activity under visible light irradiation performed and it takes 120 min for 96% degradation methylene blue. The Freundlich and Langmuir adsorption models were used to elucidate the adsorption efficiency of g-C3N4. The kinetic data depicts the pseudo first, second, and inter-particle diffusion model. Adsorption and kinetic isotherm showed that the adsorption process could be well described by pseudo-first -order kinetic model, with an adsorption capacity of 552 mg MB per gram adsorbent determined by Langmuir isotherm. These results provide some idea for the design and development of g-C3N4-based high activity photo catalysts, which is an effective strategy for organic pollutants degradation and solar energy conversion.

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