Search Results (35)

Elevated fluoride levels in drinking water pose a significant health risk for communities relying on groundwater in the Ethiopian Central Rift Valley. This study aims at characterizing real groundwater samples from the Ethiopian Central Rift Valley and evaluating the performance of an integrated membrane process based on reverse osmosis (RO) and membrane crystallization (MCr) for fluoride removal and its recovery as mixed fluoride salts. Groundwater analysis revealed fluoride concentrations of 20.8 mgL⁻¹ at the Meki-01 site and 22.7 mgL⁻¹ at the Meki-02 site, both exceeding the WHO guideline of 1.5 mgL⁻¹. In addition, total dissolved solids exceeded 1000 mgL⁻¹ at both sites, classifying the water as brackish. A commercial RO membrane demonstrated excellent fluoride and ion rejection, with fluoride removal rates exceeding 99%. The total dissolved solids (TDS) removal efficiency reached 89%. The mean water permeability of the membrane was 4.52 Lm⁻²h⁻¹bar⁻¹. The retentate produced in the RO unit reached a concentration of 70 mgL⁻¹, which was then treated using osmotic membrane distillation–crystallization (OMD-Cr) and/or vacuum membrane crystallization (VM-Cr). This process facilitated the recovery of mixed salts while achieving an almost zero-liquid discharge. The study confirms the successful removal of fluoride and its recovery as mixed salt, along with the recovery of water in an environmentally friendly and manageable way. Full article

Biological treatment processes at low or neutral pH are ineffective for gold mine wastewater treatment. The aim of this study was to develop a new cyanide-rich gold mine wastewater treatment system using alkaliphilic microbial consortia from the Ethiopian Rift Valley soda lake, Lake Chitu. The treatment setup incorporates aerobic and anoxic reactors connected in series and operated for about 200 treatment days. Simulated gold mine wastewater was formulated in the laboratory. Colorimetry was used to measure residual cyanide and reactive nitrogen molecules derived from cyanide biodegradation. Flocks and biofilms developed in the reactors during the acclimatization process. Using sodium cyanide at 200 mg/L as an initial concentration, the consortia degraded to 99.74 ± 0.08% of cyanide, with no significant variation (p > 0.05) occurring when the dose was increased to 800 mg/L. However, changes were observed (p < 0.05) at 1000 mg/L. Acetate was the preferred carbon source for the consortia. The established consortia effectively degraded cyanide to levels below the permissible discharge limit set by the International Cyanide Management Institute (ICMI). This study provides insights into the effectiveness of alkaliphilic microbial consortia derived from soda lakes for treating cyanide-polluted wastewater. Full article

Sustainable management of groundwater resources highly relies on the accurate estimation of recharge. However, accurate recharge estimation is a challenge, especially in data-scarce regions, as the existing models are data-intensive and require extensive parameterization. This study developed a process-based hydrologic model combining local and remotely sensed data for characterizing recharge in data-limited regions using a Basin Characterization Model (BCM). This study was conducted in Raya and Kobo Valleys, a semi-arid region in Northern Ethiopia, considering both the structural basin and the surrounding mountainous recharge areas. Climatic Research Unit monthly datasets for 1991 to 2020 and WaPOR actual evapotranspiration data were used. The model results show that the average annual recharge and surface runoff from 1991 to 2020 were 73 mm and 167 mm, respectively, with a substantial portion contributed along the front of the mountainous parts of the study area. The mountainous recharge occurred along and above the valleys as mountain-block and mountain-front recharge. The long-term estimates of the monthly recharge time series indicated that the water balance components follow the temporal pattern of rainfall amount. However, the relation of recharge to precipitation was nonlinearly related, showing the episodic nature of recharge in semi-arid regions. This study informed the spatial and temporal distribution of recharge and runoff hydrologic variables at fine spatial scales for each grid cell, allowing results to be summarized for various planning units, including farmlands. One third of the precipitation in the drainage basin becomes recharge and runoff, while the remaining is lost through evapotranspiration. The current study’s findings are vital for developing plans for sustainable management of water resources in semi-arid regions. Also, monthly groundwater withdrawals for agriculture should be regulated in relation to spatial and temporal recharge patterns. We conclude that combining scarce local data with global datasets and tools is a useful approach for estimating recharge to manage groundwater resources in data-scarce regions. Full article

Land degradation is a pivotal environmental concern, bearing substantial impacts in the Gidabo river basin (GRB) in Ethiopia, prompting a critical need for effective mitigation strategies. In this study, we aimed to assess the dynamics of land degradation pathways in the context of change in climate and land use. The identification of potential erosion hotspots and the appraisal of management strategies was also carried out. The Soil and Water Assessment Tool (SWAT) and the Good Practice Guidance (GPG) framework was employed. The results revealed a compelling synergy between land use dynamics and climate changes, asserting joint and individual prevalence in influencing surface runoff and sediment yield. The past simulation revealed 4–5.9% and 24–43% increments in mean annual runoff and sediment yield, respectively. While the near (2021–2040) and mid (2041–2060) future scenarios displayed varying trends under RCP4.5 and RCP8.5. Furthermore, sub-basins prone to soil erosion risk were identified, thereby enabling targeted conservation efforts. The assessment of trends in land degradation neutrality (LDN) unveiled the expansion of land degradation trajectories (by 26%) from 1985–2003 to 2003–2021. This might be attributed to the dynamic interplay between climate and land use land cover (LULC) change, with croplands and bare land emerging as high-risk degraded areas. Addressing these concerns, soil/stone bund, terracing, contour farming, and reforestation practice can significantly reduce the annual sediment yield in the future. The integration of soil erosion indicators with LDN sub-indicators can provide a more comprehensive approach that can lead to more effective land management and restoration strategies to achieve the LDN goal. The findings of this study could contribute crucial insights and substantial implications for policymakers, land managers, and conservationists. Moreover, future efforts should be directed to expand investigations into diverse land degradation pathways and mitigation measures. Full article

Since the mid-1970s, natural resource management package programs have been implemented mainly in the northern Ethiopian Highlands (Amhara and Tigray regions), providing participants with food-for-work (FFW) supported by donor agencies. Meanwhile, the government has sporadically implemented such programs in the Ethiopian Lowlands, including the semi-arid Ethiopian Rift Valley (the study area). Local villagers took the initiative to manage various natural and life resources. In this study, the following factors were determined: (i) the type of village organization that manages common-pool resources (CPRs) and controls collective work, and (ii) the kind of institutional arrangements that should be implemented in participatory CPR management and small-scale village infrastructure development programs. These issues were investigated using mixed methods research, combining multivariate analyses, interviews, and field observation. The analyses were compared specifically with advanced participatory CPR management in Tigray, northern semi-arid Ethiopia. Tigray has an indigenous labor quota system (baito) and a collective grazing land management system (hizati) at the hamlet (qushet) level. Since 1991, the Tigray government has incorporated hamlets into the local administration system and supplied FFW and other incentives to participants with a high participation rate in the baito collective work. Those institutional arrangements helped reduce soil erosion rates and restore grass and tree biomass in the area. In the study area, user groups and youth and women’s associations were (and still are) institutionally fragile CPR organizations (e.g., no bylaws). In contrast, an iddir is a robust CPR organization at the hamlet (gott) level having a labor quota system (iddir system) and funds. The requirements for sustainable participatory rural development in the two regions of semi-arid Ethiopia are, first, to institutionalize a local administration system that links the district, village, and hamlet; and second, to use various incentives provided by donor agencies to strengthen their indigenous labor quota systems. Full article

Smallholder farmers who rely on home garden agroforestry are experiencing significant impacts from climate change. To mitigate these effects, it is crucial for farmers to have access to various adaptation strategies. This study collected data from 384 randomly selected respondents in 18 kebeles over three districts, using descriptive statistics and a multivariate probit model to evaluate the factors influencing smallholder farmers’ decisions on their adaptation strategies against climate change. In Ethiopia’s Gedeo zone, this study found that smallholder farmers employ a range of adaptation methods, including expanding their agroforestry system, implementing modern agriculture techniques, conserving soil and water, diversifying their livelihoods, and employing various coping mechanisms. By analyzing data using the multivariate probit model, this study found several factors that had a significant impact on smallholder farmers’ choice of adaptation options. These factors include social network, age, education level, farming experience, household size, cultivated land size, annual income, and livestock holding. In addition, factors such as perception of climate change, previous experience of crop failure, recurrent drought, and access to information about climate change, occurrence of frost, agricultural extension contacts, access to farmer-to-farmer extension services, and perception of land infertility also influence their decision-making process. Our findings highlight the importance of improving institutional services in rural areas, promoting education on climate change, and strengthening social networks to enhance the ability of smallholder farmers to cope with the effects of climate change. Full article

As is the case elsewhere in the world, water governance in Ethiopia is a by-product of a complex set of various global and local socio-political, economic, and ecological discourses and narratives. However, the many competitive and often conflicting discourses on shaping water governance in the Ethiopian Central Rift Valley (CRV) have not been examined and chronicled. This paper investigates the different discourses, narratives, and debates of water governance and their implications for satisfying the growing demand for water. The study was grounded in political economy and political ecology theoretical frameworks. Data were collected through literature surveys and intensive fieldwork, and were analyzed following a discourse analysis and using narrative analysis techniques. The study found that the dominant competing discourses that have greatly influenced water governance in the CRV focus on decentralization, water-centered development, marketization, land/water degradation, climate change, water scarcity, and weak water governance. We suggest that the analysis and documentation of the diverse narratives and discourses from multiple perspectives could help to unravel the complex nature of water governance in the CRV and lay the foundation for attempts to implement sustainable water resource management in the region. Full article

Studies on smallholders’ determinants of soil fertility management practices have become increasingly important for boosting agricultural productivity, particularly in cereal-based farming systems in sub-Saharan Africa. In these parts of Africa, farmers preferentially apply organic and inorganic fertilizers to the fields close to their housing compounds (infields). In addition, they prefer to use more fertilizers to grow cash crops rather than food crops. Many researchers suggested that farmers use limited nutrient resources in their hot-spot fields, e.g., infields and/or cash-crop fields. Recent econometric case studies have suggested using a model that considers a complementarity or substitutability between organic and inorganic fertilizers use. This study employed bivariate probit models to analyze 524 plot data collected from the northern semi-arid Ethiopian Rift Valley. A K-means cluster analysis divided the sample data into two subdatasets, representing food-crop-based cropping system (FCCS) and cash-crop-based cropping system (CCCS). Based on narrative inquiry interviews and the cluster analysis, this study considered reflecting the structure of the local farming system in modeling: a data segmentation approach and dummy variable method. Bivariate and univariate probit analyses showed that, first, the farmers’ determinants differed between the FCCS and CCCS. Second, the correlation between organic and inorganic fertilizers use was independent. Farmers’ determinants were primarily governed by the biophysical features of the plots (commuting distance to the plot, plot size, type of the plot, etc.), which narrowed down the feasible soil fertility management options in the plot to one or two; farmers’ more specific decisions on soil fertility management practices depend on individual farmers’ socioeconomic endowments (farm holding, livestock ownership, etc.). Full article

Estimating the spatial and temporal patterns of groundwater recharge through integrated water balance modeling plays an important role in sustainable groundwater resource management. Such modeling effort is particularly essential for data-scarce regions, such as the Rift Valley Lake basin in the Basement Complex of Ethiopia, which has shallow aquifers, a proliferation of wells, and poor groundwater monitoring networks. A spatially distributed water balance model (WetSpass), along with GIS and remote sensing tools, was used for groundwater recharge estimation for its suitability and efficiency in data-scarce hydrogeological regions. The WetSpass model depicted a very good performance in simulating the groundwater recharge in the Upper Gelana watershed within the Rift Valley Lake basin. The water balance analysis revealed that about 7% of the mean annual rainfall is converted to groundwater recharge, and the remaining rainfall amounts are partitioned into surface runoff (19%) and evapotranspiration (75%). The model simulation outputs are also used to investigate the relative influences of biophysical driving factors on the water balance components. While the land use types had a greater influence on the actual evapotranspiration processes, the soil texture classes were the dominant factors in the surface runoff and groundwater recharge processes in the watershed. The groundwater recharge rates were found to be higher than 400 mm/yr in the central parts (Fisehagenent, Tore, and Gedeb) and lower than 165 mm/yr in the southern parts (Hageremariam) of the watershed. The areal proportions of the low, medium, and high recharging parts of the watershed are, respectively, estimated as 15%, 68%, and 17% of the watershed area. Therefore, the spatial and temporal patterns of groundwater recharge should be taken into consideration in developing a sustainable groundwater resources management plan for the Upper Gelana watershed. Managed aquifer recharge can be adopted in high and medium groundwater recharging parts of the watershed to capture stormwater runoff during the wet season to improve the groundwater supply during dry months. Furthermore, monthly groundwater withdrawals should be regulated according to the spatial and temporal patterns of the groundwater recharge in the watershed. Full article

Quantifying uncertainties in water resource prediction in data-scarce regions is essential for resource development. We use globally available datasets of precipitation and potential evapotranspiration for the regionalization of model parameters in the data-scarce regions of Ethiopia. A regional model was developed based on 14 gauged catchments. Three possible parameter sets were tested for regionalization: (1) the best calibration parameters, (2) the best validation parameter set derived from behavioral parameters during the validation period, and (3) the stable parameter sets. Weighted multiple linear regression was applied by assigning more weight to identifiable parameters, using a novel leave-one-out cross-validation technique for evaluation and uncertainty quantification. The regionalized parameter sets were applied to the remaining 35 ungauged catchments in the Ethiopian Rift Valley Lake Basin (RVLB) to provide regional water balance estimations. The monthly calibration of the gauged catchments resulted in Nash Sutcliffe Efficiencies (NSE) ranging from 0.53 to 0.86. The regionalization approach provides acceptable regional model performances with a median NSE of 0.63. The results showed that, other than the commonly used best-calibrated parameters, the stable parameter sets provide the most robust estimates of regionalized parameters. As this approach is model-independent and the input data used are available globally, it can be applied to any other data-scarce region. Full article

Like many other lakes in the world, the interconnected Abaya and Chamo lakes in the Southern Main Ethiopian Rift are affected by rapid sediment accumulation. Although land degradation is a well-known issue in this part of the African continent, the main sediment sources, their spatial distribution and interaction in the Abaya–Chamo lakes’ basin have not yet been documented. Here, we present a systematic inventory, characterization, and spatial analysis of landslides and gullies as concentrated sediment sources, for four representative river catchments impacted by landscape rejuvenation. Using Google Earth imagery and field surveys, we mapped with high accuracy a total of 7336 gullies and 430 landslides. Recent landslides observed during the last decade were few, small and shallow, and appear to have played a minor role in the current sediment dynamics. Large landslides are old and inactive. Although they do not contribute to the current sediment budget, they contribute indirectly to landscape dynamics by favoring the occurrence of gullies. Overall, large percentages of severe to extremely degraded areas of gully erosion are located in rejuvenated landscapes, especially at the level of the old landslides. Many active gullies are connected to the river network, as such acting as the source of sediment. Our analysis is a step towards understanding the nature and control of anthropic activities on sediment production in the region. We also highlight the importance of considering the interactions between sediment sources and the connectivity of the geomorphological system. Full article

Increasing pollutant emissions in the Lake Hawassa watershed (LHW) has led to a severe water quality deterioration. Allocation and quantification of responsible pollutant fluxes are suffering from scarce data. In this study, a combination of various models with monitoring data has been applied to determine the fluxes for Chemical Oxygen Demand (COD), Biochemical Oxygen Demand (BOD₅), Total Dissolved Solid (TDS), Total Nitrogen (TN), Nitrate and Nitrite-nitrogen (NOx-N), Total Phosphorous (TP) and phosphate (PO₄-P). Water, wastewater and stormwater samples were collected and analyzed at eight monitoring stations from rivers and point sources and six monitoring stations of stormwater samples. The flow simulated with soil and water assessment tool (SWAT) could be very well calibrated and validated with gauge data. This flow from SWAT model, measured flow during monitoring and pollutant concentrations were used in FLUX32 to estimate pollutant fluxes of main rivers and point sources in LHW. The formulas provided by Ethiopian Roads Authority and Gumbel’s theory of rainfall frequency analysis was employed to determine the 2-years return period rainfall depth for the City of Hawassa. The integration of HEC-GeoHMS and SCS-CN with the catchment area enabled to determine stormwater pollution load of Hawassa City. The estimated pollutant flux at each monitoring stations showed that the pollutant contribution from the point and nonpoint sources prevailing in the study area, where the maximum fluxes were observed at Tikur-Wuha sub-catchments. This station was located downstream of the two point sources and received flow from the upper streams where agricultural use is predominant. Furthermore, Hawassa city has been identified as a key pollutant load driver, owing to increased impacts from clearly identified point sources and stormwater pollutant flux from major outfalls. Agricultural activities, on the other hand, covers a large portion of the catchment and contributes significant amount to the overall load that reaches the lake. Thus, mitigation measures that are focused on pollutant flux reduction to the lake Hawassa have to target on the urban and agricultural activities. Full article

Fluorosis is a major public health problem in the Rift Valley of Ethiopia. Low calcium (Ca) intake may worsen fluorosis symptoms. We assessed the occurrence of fluorosis symptoms among women living in high-fluoride (F) communities in South Ethiopia and their associations with dietary Ca intake. Women (n = 270) from two villages provided clinical and questionnaire data. Dental fluorosis examination was done using Dean’s Index, and skeletal and non-skeletal fluorosis assessment was carried out using physical tests and clinical symptoms. Daily Ca intake was estimated by a food frequency questionnaire. Food, drinking water and beverage samples were analyzed for F level. Many subjects (56.3%) exhibited dental fluorosis. One-third of the women were unable to perform the physical exercises indicative of skeletal fluorosis; about half had ≥2 symptoms of skeletal/non-skeletal fluorosis. The average F level in drinking water sources was ~5 mg/L. The F content in staple food samples varied from 0.8–13.6 mg/kg. Average Ca intake was 406 ± 97 mg/day. Women having ≤400 mg/day Ca intake had ~3 times greater odds of developing skeletal rigidity with joint pains [AOR = 2.8, 95%CI: 1.6, 5.0] and muscular weakness [AOR = 2.9, 95%CI: 1.3, 6.3] compared to those with higher intakes. No association of calcium intake was seen with dental fluorosis. As low dietary Ca intake was associated with symptoms related to skeletal and non-skeletal fluorosis, this warrants nutritional intervention on calcium intakes in this setting. Full article

Several studies have shown the presence of fluoride levels much higher than the 1.5 mg/L threshold concentration recommended by WHO in the spring waters and wells of the Ethiopian Rift Valley. Available defluoridation techniques can be costly, present complicated technical aspects, and show limited effectiveness. Therefore, it is necessary to devise innovative, sustainable, and effective solutions. This study proposes an alternative method of intervention to the known techniques for removing fluoride from water, particularly suitable for smaller rural communities. In particular, in this work, the possibility to use electromagnetic fields as a physical method for removing the excess fluoride was investigated. The study was carried out by developing a multiphysics model used for studying and envisaging the design of a device. In this framework, the combination of this approach with the use of highly reactive smectite clay was numerically studied. The results obtained, although preliminary, indicate that the proposed system could significantly impoverish the waters of the Rift Valley from fluoride, with the consequence of obtaining a resource suitable for human consumption, in particular for rural communities. However, further theoretical investigations and experimental phases will be necessary to achieve the desired results. Full article