Africa Center of Excellence for Water Management

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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 Drinking WaterQuality from Source to Point Use (The Case of Mojo Town, Oromia Regional State of Ethiopia)
(Addis Ababa University, 2020-07-25) Mohammed, Fedila; Mogess, Beshah (PhD); Zewege, Feleke (PhD)
The quality of drinking water has deteriorated due to insufficient treatment plant, direct discharge of untreated wastewater, and ineffective management of piped water distribution systems. The study was conducted on assessing drinking water quality from source to point of use in Mojo town in Oromia region. To achieve the goal of this study, fourteen water samples were collected from different sources and from a household tap, using the purposive sampling method. The pH, turbidity, total dissolved solids (TDS), iron, ammonia, residual free chlorine, fluoride, nitrates, sulfates, total hardness, and Microbiological (total coliforms and faecal coliform bacteria) parameters were determined using laboratory analysis. Laboratory results of bacteriological analysis indicated 66.67% of household tap water samples in kebele two and 60% of water samples in kebele one indicating the presence of total coliforms. On average, 25% of the total household tap shows the presence of faecal coliforms. This is due to a poorly maintained distribution network, improper waste management and broken piping materials. Based on the laboratory results, a large proportion of the community gets the ammonia concentration. 75% of household and 60% of borehole water samples were exceeding the recommended value by the World Health Organization and the national standard. The highest temperature was recorded at BH1, BH2 and BH3 (25,31,29) respectively which is 60% of the total borehole water samples. Turbidity measurements taken from tap water samples especially around kebele one namely HH4, HH5 and HH6 were found to be higher than the recommended value. In addition, a relatively high level of fluoride was observed in BH5. 21.43% of the water sample of the total Iron above WHO recommended level (0.3 mg/l). In addition, a high amount of nitrate concentration was observed in most of the household and borehole samples. All remaining physical and chemical parameters were safe and within acceptable drinking water quality range. In conclusion, poor sanitation, low level of hygiene, and uncontrolled disposal of solid and liquid waste were among the causes of water pollution in the study area. In addition, it is also recommended that the current state of the Mojo water quality system be improved, the proper management of both liquid and solid wastes, the promotion of improved sanitation practices and the constant inspection of water quality.
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.
Assessment of Land Use Cover Change Impact on Stream Flow and Sediment Yield Case Study on Gilgel Gibe III Reservoir Omo Gibe Basin
(Addis Ababa University, 2021-11-17) Berihun, Rediet; Kidane, Hadush (PhD)
Land use/land cover (LULC) change is an important landscape process capable of altering the fluxes of water, sediment, contaminants and energy. In this study, Soil and Water Assessment Tool (SWAT) model was used to examine the effects of LULC on the hydrological process of Gibe III Watershed in the Omo-Gibe basin. The performance of the model was evaluated through sensitivity, uncertainty analysis, calibration and validation. The LULC change analyses for two periods (2009 and 2019) were used for estimation of stream flow and sediment yield. The result has shown that during the study period most parts of the forest land were converted into cultivated land with an increase of cultivated land by 6.97%, which resulted in an increase of stream flow and sediment yield by 4.7 m3/s and 0.53 ton/ha/year respectively. The Nash sutcliff efficiency (NSE), coefficient of determination (R2) and percent of bias (PBIAS) were used for evaluating the model performance. The model results have shown a good and satisfactory agreement with the observed values with NSE > 0.51, R2 > 0.63, and PBIAS < 6.45. values. Based on the validated sediment yield results of 2019 land use, high potential source of spatial variability of sediment yield identified within the watershed. Hence, for the critical sub-watersheds, the design and development of three best management practices (BMPs) were performed. These best management scenarios include: S1 (filter strip), S2 (terrace/ bund) and S3 (reforestation). Based on these scenarios, the findings have shown a sediment yield reduction by 41.56%, 32.49% and 53.77% with the implementation of S1, S2 and S3 respectively. Therefore, based on the findings, implementing S3 is the best management strategy as compared to other options and hence, such intervention should be encouraged at a wider scale for efficient sediment reductions of Gibe III watershed
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.
Assessment of the Effect of Artisanal Gold Mining on Heavy Metals Concentrations and Associated Potential Public Health Risk: The Case of May Sieley River of the Shire , Tigray, Region Ethiopia
(Addis Ababa University, 2021-02-19) Elias, Habineza; Kifle, Demeke (PhD)
Artisanal gold mining (AGM), in third world countries including Ethiopia has become a livelihood diversification strategy, which makes significant contribution to poverty alleviation. Although artisanal gold mining provides enormous economic benefits, the mining activities are carried out at the expense of the environment and public health due to pollution with heavy metals (HMs). The protection of public health and aquatic resources necessitates the availability of scientific information on pollution with heavy metals. The present study was, therefore, conducted to investigate the efffect of artisanal gold mining on the levels of selected heavy metals in May Sieley River (Tigray) and evaluate the potential human health risk. Surface sediment and water samples were collected from upstream, midstream and downstream sites (USS, MSS &DSS) respectively, during the dry and post-rainy periods and were analyzed for Pb, Cd, Cu, As, Cr, Hg, Ni, and Zn by Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES). The concentrations of heavy metals in water samples were compared with WHO and Ethiopian standards for drinking water and assessment of human health risk was made following the guidelines provided by the US Environment Protection Agency. Temperature, pH and dissolved oxygen were measured insitu and were found to be within acceptable ranges and did not show large variations. The differences in HMs concentrations in water among sampling sites during both seasons were not marked except for Cu and Zinc in dry season, although Zn, Cu, Hg, Cd and Pb were higher at the MSS suggesting the association of their levels primarily with AGM. The differences in the concentrations of all HMs in water samples between seasons were marked. The concentrations of HMs in sediment samples varied markedly between the two seasons. The differences in HMs concentrations in sediments among sampling sites during dry seasons were marked for Cu, Zn, Pb and As while in post-rainy season, differences were not marked except for Ni and Pb. The concentrations of all HMs except Nickel in sediment samples of the dry season were higher at the MSS, while they were higher at USS during the post-rainy season. The present results suggest that both AGM and natural sources associated with the weathering of rocks have made contributions to the metal pollution of May Sieley River. Hg and As were above WHO and Ethiopian standards for drinking water in the dry season in all sampling sites, while Cr, Cd, Pb and As were above the same standards for drinking water in the post-rainy season in all sites, except Hg (in one sample of MSS) and Ni (in one sample of DSS). The HQ values for As, Pb, Hg and Cd for both age groups were at unacceptable non-carcinogenic potential health risk levels (HQ>1), while As and Cd for adults and As, Cd and Hg for children, are likely to have chronic effects (Q>10). The Sum of HQs (HI) of analyzed metals was far greater than 1 for both age groups, children being at greater risk. This raises concern about the non-carcinogenic adverse health effects of using the river water for drinking and other household purposes. The results of the ILCR assessment for Arsenic, Lead, Cadmium, Chromium and Nickel indicated that the carcinogenic effect associated with these metals is not acceptable. The study has revealed that the river water is not safe due to HMs pollution, AGM should be managed to reduce its contribution to the pollution of water bodies with heavy metals. The government needs to assist and empower the miners so that they can carry out their activities sustainably and in an environmentally friendly way. Further monitoring of the impact of traditional gold mining on HMs pollution by considering aquatic organisms in order to assess their biomagnification along the food chains is also recommended.
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.
Carbon Storage and Fluxes from a Tropical Freshwater Wetland in Uganda: Implications for Climate Change Mitigation
(Addis Ababa University, 2021-06-26) Were, David; Kansiime, Frank (Professor); Fetahi, Tadesse (Professor)
Natural wetlands have been shown to be among the most important ecosystems in climate change mitigation, through carbon (C) sequestration. However, natural wetlands also act as C sources, emitting part of the sequestered C back into the atmosphere, in form of carbon dioxide (CO2) and methane (CH4). Storage and emission of C are of interest in tropical wetland studies because the high and relatively stable temperatures year-round enhance both primary productivity and organic matter decomposition. However, most of the studies on C sequestration and emission have mainly focussed on temperate and boreal wetlands. Further, many natural tropical freshwater wetlands are increasingly being converted into rice paddies, with limited knowledge on its impact on wetland C balance. This study investigated soil organic carbon (SOC) storage and emission of CO2 and CH4 from a tropical freshwater wetland in Uganda, under natural and rice paddy conditions. The natural section is dominated by Cyperus papyrus (Papyrus), Typha latifolia (Typha) and Phragmites mauritianus (Phragmites) vegetation communities. Soil samples for determination of SOC were obtained up to 50 cm depth, using a Russian peat borer, while CO2 and CH4 gas samples were obtained using static flux chambers. Within the natural wetland section, SOC content (123.7±2.6 [mean±SE] g C kg-1 dry soil) in Papyrus was significantly higher (p < 0.05) than those obtained in Typha and Phragmites. On the other hand, there was no significant variation (p > 0.05) in SOC contents of Typha and Phragmites. Comparing SOC contents of the natural and rice paddy wetland sections, all the three vegetation communities of the natural section had SOC contents (Papyrus = 123.7±2.6, Typha = 85.3±1.1 and Phragmites = 78.2±3.4 g C kg-1 dry soil) significantly higher (p < 0.05) than that recorded in the rice paddy section (39.7±0.7 g C kg-1 dry soil). Considering fluxes of gases from the wetland, variation among the vegetation communities of the natural section was only noticed in Phragmites during the dry season. During this season, Phragmites showed significantly higher flux (p < 0.05) of CO2 (871.8±56.7 mg C m-2 h-1) and lower (p < 0.05) flux of CH4 (8.7±0.5 mg C m-2 h-1) than those measured in both Papyrus and Typha. No significant variation in gas fluxes (p > 0.05) occurred among the vegetation communities during the wet season, for both CO2 and CH4. Further, comparing the natural and rice paddy wetland sections, variabilities in gas flux rates were observed. CO2 fluxes (mg C m-2 h-1) from the rice paddy section during the dry and wet seasons were 1045.4±46.6 and 804.4±50.2 respectively, both significantly higher (p < 0.05) than those obtained in all the three vegetation communities of the natural section. However, CH4 fluxes from the rice paddy section during the dry and wet seasons were 2.1±0.4 and 5.1±0.5 mg C m-2 h-1 respectively, both significantly lower (p < 0.05) than those observed in all the three vegetation communities of the natural section. Nevertheless, considering total C flux (summation of CO2 and CH4 fluxes), it was observed that the rice paddy wetland section emitted significantly higher (p < 0.05) C than the natural section. Plant biomass density, and soil physico-chemical characteristics: bulk density, salinity, pH and temperature significantly correlated (p < 0.05) with SOC, while water level had a significant correlation (p < 0.05) with CO2 and CH4 fluxes in both sections of the wetland. The observation of significantly higher SOC content and significantly lower total C flux from the natural wetland section compared to the rice paddy section suggests that conserving a natural tropical freshwater wetland is a better climate mitigation option than converting into a rice paddy wetland.
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-
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.
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.
Development of a Point of Use Drinking Water Purifier Using Aluminium Oxide Based Flocculent Disinfectant Composite
(Addis Ababa University, 2021-07) Namate, Patricia; Zewge, Feleke (PhD)
The United Nations officially declared access to clean drinking water and sanitation to be a human right in 2010. Despite this, one in every three people in the world still lacks access to clean drinking water. A lot of people suffer from water-borne diseases as a result of contaminated drinking water. Aside from microbiological pollution, high fluoride content in drinking water is one of the most serious problems in African countries. The present study aimed to contribute to the availability of clean water by developing a point of use drinking water purifier using aluminium oxide-based flocculent-disinfectant composite. The study involved the preparation of aluminium oxide (AO) prepared from locally available aluminium sulphate (alum) using a standard method. This was followed by batch experiments to investigate different parameters that affect the efficiency of fluoride removal and E. coli log reduction by the developed method. A dose of 75mg/L AO, 800 mg/L alum, 35% lime and 1.5 mg/L calcium hypochlorite achieved 95% fluoride removal efficiency and 5 log 10 reduction of E. coli using 15 mg/L as initial fluoride concentration and 105 CFU/100 mL E. coli concentration. The optimum contact time was found to be 30 minutes. Initial fluoride concentration affected fluoride removal but showed no effect on E. coli inactivation. The optimum pH of the solution for both fluoride removal and E. coli log reduction was found to be in the range of 4-8. E. coli concentration did not affect fluoride removal. The fluoride removal efficiency and E. coli log reduction were tested on real water samples from the Ethiopian Rift Valley. The results showed that water samples from Rift Valley required a high dose of alum, AO and calcium hypochlorite and a low dose of lime. Three prototypes were developed as high dose, medium dose and low dose for treating water samples with 5 mg/L, 10 mg/L and 15 mg/L fluoride concentrations. The prototypes are powdered form packed in sachets. The high, medium and low doses weigh 11.9 g, 10.6 g and 9.9 g, respectively. The prototypes were tested on real water samples from the Ethiopian Rift Valley and the results were found to be within the drinking water standards. The present study showed that the developed product has the potential to purify drinking water contaminated with fluoride and disease-causing microorganisms. This study suggests that the product should be tested at a pilot scale and upon its success, the product could be manufactured at a larger scale to which communities without access to portable water would use the product for treating drinking water at a household scale.
Distillery Stillage Water Pollution Control: An Integrated Approach for Efficient Treatment and Recovery
(Addis Ababa University, 2021-05-26) Dagnew, Getachew; Alemayehu, Esayas (Professor); Chebude, Yonas (Professor); Mekonnen, Andualem (Professor)
In spite of the increasing demand for potable and fuel ethanol, the distillery industries continue to be a major source of surface water and soil pollution, especially to developing nations, due to the release of a highly organic and complex byproduct- the stillage. Stillage contains solids, recalcitrant organics, persistent color, sulfate, chlorides, phosphorus and nitrogen, whose recovery and treatment plays a major role in environmental sustainability. In most cases, the application of single stillage treatment technology did not succeed. The objective of this study was to quantify molasses and stillage byproducts in Ethiopia and examine the feasibility of an integrated treatment approach towards sustainability. Standard methods were applied, beginning from a systematic literature review through primary data collection, stillage sampling and conducting a series of experiments. The trials were set-up based on a sound design followed by standard analytics and a statistical analysis of the results. The experiments started with determining the biochemical methane potential (BMP) test and then undertaking a mild iron oxide coated sand (IOCS) based wet air pretreatment (WAp) through anaerobic digestion (AD), adsorption and a polishing aerobic degradation. From a quantitative characterization study, Ethiopia currently produces close to 1.8 million tons of cane sugar, with the release of over 300,000 tons of molasses as a by-product. Using cane molasses as a raw material and with the release of 431,000 m3 of stillage into the environment, the potable ethanol industry in the country produces over 33,000 m3 of ethanol annually. According to the BMP test run for 45 days at mesophilic condition, molasses stillage has the potential of giving 139 NmlCH4/g-COD with 68% purity. A mild IOCS based WAp of the stillage sample at 3.5% IOCS loading, a temperature of 60 oC, which was held for four hours at atmospheric pressure brought the desirable effect in detoxification. The result observed following comparison of raw and treated stillage from E. coli incubation at 37 oC and 86 revolutions per minute of shaking demonstrated a statistically significant difference (p-value = 0.02) in toxicity. Successively, the consequence of a mild, IOCS based WAp on the methane (biogas) yield as well as the biochemical oxygen demand (BOD) and COD removal was compared with the raw counterpart using batch mesophilic (35±2 oC) AD of stillage. Further, the effect of applying scoria (a highly vesicular igneous rock) support on AD process stability and performance was assessed for the first time. Consequently, a statistically significant (p-value < 0.05) difference in the cumulative specific raw without scoria support, raw with scoria support and WAOp scoria supported stillage AD subsequently. The soluble COD (CODsol) after AD of stillage with scoria, without scoria and with scoria and WAp in mg/l was 30041.7, 30666.7, and 13375.0 respectively. With the WAOp and scoria supported stillage AD a BOD and COD reduction of ≈100% and 92% were achieved. These achievements are unique in stillage recovery and pollution remediation findings so far. Further, the biogas yield with respect to the reaction days (within 18 days) with a relatively stable process (average pH=7.7, 6.8 and 6.7 for pretreated and untreated stillage with scoria and without scoria) was hastened due to pre-treatment. Regarding the adsorption trial on stillage after the batch AD, all the significant COD removals were observed after three hours of contact time for all doses of the treated scoria adsorbent. Maximum removal rate was at 0.03 mg/ml of scoria dosing and in three hours contact time whereby the final COD of the stillage did go lower only to 7500 mg/l. In a related experiment, the effect of organic loading rate (OLR) and stillage WAp was studied in a continuous AD in scoria-packed column reactors. The removal of stillage COD was significantly better (p-value = 0.036), with an average of 13% difference, due to pre-treatment of stillage with an increased OLR to 2000 mg/L-d. In a further polishing aerobic treatment trial of the effluent from the stillage batch AD, a complete removal of the BOD and significant removal of COD, with an average effluent COD of 2278 mg/L was achieved. In fact, 68% of the COD removal occurred within eight hours of digestion. Despite the persistence of color, the removal of organics with bioenergy recovery from integrating the WAp, the batch AD and the aerobic remediations (˜99% COD and 100% BOD removals) of stillage appear to be a promising technique in its sustainable management while adhering to the regulators’ discharge limits.
Diversity, Relative Abundance and Socio-economics of Fish and Fisheries in the Western Part of Lake Tana, Ethiopia
(Addis Ababa University, 2020-11-15) Tegegne, Sewunet; Getahun, Abebe (Professor)
The fishery resource in Lake Tana has significant socio-economic contribution through generating income, employment and used as a cheap protein source for local people. However, diversity, relative abundance and socio economics of fisheries in the western part of Lake Tana were not well studied. So the aim of this study was to investigate diversity, relative abundance and socio economic value of fisheries in the western part of Lake Tana. The study was conducted from December 2019 to August 2020. Data were generated from field sampling, fishermen catch observations, key informant interviews, focus group discussions and through questionnaires. At the sampling sites, physico-chemical parameters were measured using MPS. Fish weights were measured from the fishermen catch at the landing sites. Data were analyzed by (PAST), SPSS software and by various descriptive statistics. A total of 6118 fish specimens were collected at all sampling sites. Thirteen fish species were identified with species diversity value 1.6. The evenness value in the western part of Lake Tana was J=0.62. All the fish species were present in all sampling sites, except that L. gorgorensis was absent at the sites of Kunzila and Delgi. O. niloticus (46.24%) was the most abundant species in number and C. gariepinus (28.39%) was the second and L. gorgorensis (0.6%) the least abundant species. From the value of (% IRI), Oreochromis niloticus was the most important species during the dry season with value of 22.48 % and C. gariepinus was the most important species with the IRI value of 32.67% during the wet season. L. crassibarbis was the least important species with the IRI value of 0.23% during the dry season and L. gorgorensis was the least important species in the wet season with the IRI value of 0.31%. 18.16 % of variance was positively correlated with environmental variance with C. gariepinus, L. nedgia, L. truttiformis, L. tsanensis and O. niloticus. The total fish catch composition in the study area were O. niloticus (54.3%), C. gariepinus (23.4%) and Labeobarbus spp. (22.3%). The fishing activities in the study area were 87.8% fishing alone and 12.2% fishing in groups. The majority of fishermen were used monofilament gillnets (64%) and only 36% used multifilament gillnets. The fishermen who fished alone and those in groups had an average income of 1907.75 and 3210.42 ETB, respectively (P< 0.05). The average income who had owned modern and traditional boats were 3300.00 and 1907.75 ETB, respectively: (P<0.05). The current fishing trends in the study area and the fishery conditions were threatened. Therefore, appropriate management action should be taken especially to control monofilament fishing gears in order to sustain the fishery resources in Lake Tana.
Drinking Water Quality and Management Practices From Source to Household: The Case of Kombolcha Town, Ethiopia’
(Addis Ababa University, 2020-06-13) Tesfaye, Bezawit; Alemayehu, Esayas (Professor); Zewge, Feleke (PhD)
This research focuses on investigation of the existing drinking water quality of Kombolcha town from the source to points of household tap in relation to safety and acceptability for users concerning water quality parameters. The town gets its water supply from groundwater sources. A total of 45 water samples were selected and collected from boreholes, reservoirs, distribution mains and households. The pH, Turbidity, Total Dissolved Solids (TDS), Electrical Conductivity (EC), Temperature, Total hardness, free chlorine residue, Manganese, Nitrate and Iron and Microbiological (Total Coliform and fecal Coliform) parameters were determined. The result was then compared with the WHO and Ethiopian water quality standards. The results obtained show that for physical analysis except temperature the rest all parameters were within the WHO permissible limit. The results for temperature were found between the ranges of 22.5°C - 26.1°C. Based on laboratory analysis of chemical parameters the result shows that total hardness is above the permissible limit set by the guidelines. Also, all chlorine residual of the samples were found to be below the recommended values of WHO and national guidelines except seven of samples. However manganese, iron and nitrate were within the permissible limit. The result of bacteriological analyses indicated that Fecal coliform of all samples were zero meeting WHO and national guidelines. But Total coliform of nine samples were above the guideline`s limit ranging between 1-4 CFU/100ml. In summary, with regard to the Physico-chemical parameters the water is safe and there is no significant effect on the health of the users. The results of bacteriological analyses have shown that some of the sample points are at risk. To overcome these problems regular chlorination is recommended. It is also recommended that sampling and monitoring at different times is essential and analysis of additional water quality parameters should be undertaken.
Ecological and Socio-economic Impacts of Ecohydrological Interventions on the Wetlands along the Southeastern Shore of Lake Tana, Ethiopia
(Addis Ababa University, 2020-10-18) Asnakew, Eshete; Mengistou, Seyoum (Professor); Wondie, Ayalew (PhD); Zerihun, Yohannes (PhD)
Information regarding the ecological and socio-economic impacts of ecohydrology based intervention approach in the wetland ecosystem plays an indispensable role in increasing biodiversity, improve water quality and enhance ecosystem services. Although ecohydrological solutions have been proposed by various studies for immediate, nature based, management to prevent degradation from imminent developments, a comprehensive study on the impacts of ecohydrology intervention in relation to biological, physico-chemical and socio-economical aspects are limited. Such information is very important for the management of degraded shore wetlands of Lake Tana. Thus, the aim of this study was to investigate the impacts of ecohydrological intervention in relation to physical, chemical and biological attributes and assess the most common socio-economic benefits of the wetlands in Lake Tana shore. Ecological and socioeconomic impacts of ecohydrological intervention on the wetlands in the shore of Lake Tana were studied in November 2019 and April 2020. Physico-chemical data were measured on each sampling point. Sediment and water samples were measured and analyzed onsite and in the laboratory and most of the Physico-chemical parameters were significantly different (p<0.05) across the sampling sites. The quadrat/transect method was employed to collect macrophyte and macroinvertebrate data. Quantitative characteristics of macrophyte sampling were conducted using transect and quadrat method along vegetation and water depth gradients. A total of 24 quadrats of 1m×1 m size were employed using the species-area curve method for all sampling sites. A total of 12 major macrophytes species were recorded from all sampling sites. The abundance of macrophytes varied between sampling sites and season and this might be attributed to the differences in protection status, human disturbances, physico-chemical parameters and level of awareness of the community. Based on the Shannon diversity index (H' = 0), the Agid kirgna wetland could be grouped under the least diverse followed by Gedromesk wetland (H' = 1.00) and Gumetirs wetland (H' = 1.24). A total of 975 macroinvertebrate individuals belonging to 15 families were collected using a D-frame net from all sampling sites during the study period. Based on the biological indices, H' = 2.39 and HFBI=4.68, the Gumetirs wetland might be grouped under a good ecological condition. Both phytoplankton and zooplankton samples were collected using a 15μm mesh size plankton net. A total of 23 phytoplankton and 9 zooplankton taxa were collected. Numerical density and diversity of zooplankton and phytoplankton taxa varied along the sampling sites, habitats and seasons which could be linked with food availability, degree of disturbance and physico-chemical conditions. Qualitative and quantitative data were collected from 90 households head (HHDs) on several variables through structured questionnaire, interview and observation to assess the socio-economic benefits of the wetlands. Overall results of this study confirmed that biological, physico-chemical conditions and wetland benefits were associated with the intensive human activities carried out in and around the wetlands, and level of awareness of the local communities. Therefore, emphasis should be given to the factors which may lead to the degradation of wetland resources within and its catchment especially recession farming, overharvesting, overgrazing and invasion of water hyacinth. Immediate ecohydrology based intervention approaches should be implemented to conserve and minimize further degradation and ensure sustainable livelihoods of wetlands along the shore of Lake Tana.
Effect of Soil Tillage Systems on Soil Hydrological Processes in Common Bean (Phaseolus Vulgaris L.) Farms in Mukono District, Uganda
(Addis Ababa University, 2021-07-13) Fatumah, Nakiguli; Tilahun, Seifu A. (PhD)
Goal 15 of the United Nations 2030 Agenda for Sustainable Development addresses the protection, restoration, and promotion of sustainable use of terrestrial ecosystems by halting and reversing land degradation. Soil tillage is one of the main factors causing land degradation in sub Saharan Africa. In this study, the effect of soil tillage systems on infiltration rate, soil moisture content, soil water storage, surface runoff volume, suspended sediment concentration, and sediment yield in common bean (Phaseolus Vulgaris L.) farms, at Goma and Kimenyedde experimental sites in Mukono District, Uganda was evaluated. The study also assessed the effect of soil tillage systems on grain yields, water use efficiency, and economic returns of the common beans. The study further evaluated the performance of the Agricultural Policy/Environmental eXtender model in the simulation of surface runoff volume and sediment yield. The soil tillage systems were: no-tillage, stubble-mulching, deep tillage, and conventional tillage. Field experiments were arranged in Complete Block Design under four soil tillage systems, consisting of two tillage directions: tillage down the slope and tillage perpendicular to the direction of slope during three wet seasons. The results showed the highest and lowest infiltration rate and soil moisture content under no-tillage and conventional tillage, respectively. No-tillage and stubblemulching improved soil water storage by 46 and 45%, respectively, compared with conventional tillage in the 0-100 cm soil depth over the 16 months. The highest surface runoff volume was observed during the third season at Goma site under conventional tillage with tillage down the slope (1082 mm), while the lowest surface runoff volume was observed during the second season in Kimenyedde site under no-tillage (165 mm). Tillage perpendicular to the direction of slope reduced surface runoff volume by the range of 5-15%, relative to tillage down the slope. The highest and lowest suspended sediment concentration were observed under conventional tillage (2.65 ± 0.5 g L-1) at Goma site during the third season and no-tillage (0.43 ± 0.1 g L-1) at Kimenyedde site in the second season, respectively. Sediment yield was highest under conventional tillage at Goma (183.01 kg ha-1) during the third season and lowest under no-tillage (9.19 kg ha-1) at Kimenyedde site, during the second season. Soil tillage systems significantly (p < 0.05) affected water use efficiency, with water use efficiency values generally greater under no-tillage and stubble-mulching than under deep tillage and conventional tillage. Grain yield was highest under no-tillage and stubble-mulching than deep tillage and conventional tillage, with over 5, 38, and 43% higher grain yield under no-tillage than under stubble-mulching, deep tillage, and conventional tillage, respectively. Seasonal precipitation distribution considerably influenced crop yield, soil water storage, and water use efficiency. The net profit was three and five times higher under no-tillage than under conventional tillage and deep tillage, respectively. No-tillage and stubble-mulching were the optimum soil tillage systems for increasing infiltration rate, soil water storage, enhancing water use efficiency, improving grain yield and economic returns in central Uganda. Evaluation of Agricultural Policy/Environmental eXtender model performance for surface runoff volume and sediment yield simulation provided good results. For both calibration and validation periods, Nash-Sutcliffe efficiency values were > 0.5, coefficient of determination > 0.6, and percent bias values were within ±20% for surface runoff volume and sediment yield. The Agricultural Policy/Environmental eXtender model can be a useful tool for evaluating surface runoff volume and sediment yield for different management practices in Mukono District. Adopting no-tillage and stubble-mulching would be efficient strategies for controlling excessive surface runoff and sediment in the region.
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.
Effects of Water Hyacinth-based (Eichhornia Crassipes) Vermicompost Tea (Aqueous Extract) Supplement on Growth Performance of Lettuce Under Non-Circulating Hydroponics and Aquaponics System
(Addis Ababa University, 2020-11-14) Ruth, Upile; Geremew, Akewake (PhD)
The study was conducted to determine the effects of water hyacinth-based (Eichhornia crassipes) vermicompost tea (aqueous extract) supplement on growth performance of lettuce under the non-circulating hydroponics system. Water hyacinth is nutrient-rich and can undergo vermicomposting and be used in hydroponics or aquaponics production systems. The purpose of this study was to investigate the potential use of water hyacinth-based vermicompost tea material in a hydroponics system for an improved product of lettuce and management of water hyacinth through utilization. The study used a systematic random sampling design to obtain the sample size of a total of 33 plants per unit. To compare the effect of various dilutions of water hyacinth based vermicompost tea and the growth performance of lettuce in non-circulating hydroponic and aquaponic systems leaf area, shoot length, root-shoot ratio, growth rate, moisture content analysis, were used. Ash and digesting methods were used to determine the effect of various dilutions of hyacinth-based vermicompost tea on the concentration of selected nutrients and heavy metals in lettuce. Lettuce dosed with hydroponics nutrient solution were significantly different at (P<0.05) from lettuce supplied with water hyacinth-based vermicompost extract dosed at 30%, 40% and 60%, the plants had a higher growth rate, shoot length and moisture content, large leaf area and a small root-shoot ratio. Lettuce dosed with vermicompost tea was resistant to aphid and fungi attack, while the ones dosed with synthetic solutions were attacked. Yield from hydroponics and aquaponics system was not significant. Lettuce dosed with WHBVCT were short in nutrient content in their solutions while the ones with synthetic solutions had enough nutrient supply. Lettuce dosed with WHBVCT had nutrient and heavy metal concentrations within the permissible limit, except for treatment dosed at 30% and 40% which showed a higher Pd and Zn values. WHBVCT is rich in chitinase, phenols and alcohol which digest the chitin of insects and phenol and inhibit the growth of fungus and spread of insects which made lettuce with WHBVCT more resistant than the others. Therefore, WHBCVT can be used to control aphids and fungus, but it cannot be used for lettuce production non-circulating hydroponics and trials have to be made on fruiting vegetables to observe its performance.
Evaluating Methods and Polarizations of S-1 Sar for Time-Series Flood Hazard Mapping Akaki Catchment
(Addis Ababa University, 2021-06-06) Worku, Tilaye; Tamiru, Alemseged (PhD)
Lack or absence of data is the main limiting factor for studying flood hazard and risk in many basins across the globe. The Google Earth Engine (GEE) has a potential to narrow data gaps by providing ease of access to remote sensing data and enabling automatic and rapid generation of flood inundation map for Near Real-Time monitoring. In this study, GEE was used to assess and analyze the Sentinel-1 (S-1) Synthetic Aperture Radar (SAR) dataset for flood inundation mapping in the Akaki catchment which hosts Addis Ababa city in the central part of Ethiopia. Ground Control Points were collected at the time of satellite overpass for evaluating the accuracy of the generated flood inundation maps. Change detection and Histogram thresholding methods were compared using co-polarized (VV) and cross-polarized (VH) images. A new method which is Root of Normalized Image Difference (RNID) was developed for change detection. Major flood affected roads in Addis Ababa city and Land Use Land Cover (LULC) classes were detected from April to November of 2017 to 2020. The result shows the RNID method performed better than the histogram thresholding for flood inundation mapping in the study area. The VH polarization performed better than the VV polarization to detect the lower signal backscatter intensity generated from the flooded surface. An overall accuracy of 95% and kappa coefficient 0.86 was obtained when applying the RNID method and VH polarization. In the Akaki catchment, the remote sensing mapping showed that the flood commonly starts in May and recedes in November, but flood was frequent and widespread from June to September. At the downstream of the new expressway, the riverine and pluvial flood frequently occurred in the past four years. The flood inundation map also showed that several major roads of Addis Ababa are affected by flooding. The irrigated and built-up area were the most affected land use classes with an inundation extent of 1057.05 ha (21.28% of the total irrigated land) and 544 ha (1.44% of the total urban area) respectively. The S-1 SAR was found useful for time series flood inundation mapping and the new change detection method (RNID) performed better in urban and peri-urban flood mapping, but the accuracy of the flood map varies with the flood detection method and the image polarization.

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