Kulfo River Research Articles

Landslide susceptibility modeling in the Kulfo river catchment, rift valley, Ethiopia: An integrated geospatial and statistical analysis

Landslides occur when debris, rocks, or soil particles move downward. Examining the susceptibility of landslides is essential for safeguarding human well-being and assessing the consequences of landslides on the natural surroundings and ecosystems. This study utilized the frequency ratio technique to evaluate the probability of landslides happening in the Kulfo River watershed, situated in the Rift Valley area of Ethiopia. In order to ensure a comprehensive analysis, many data sources were employed, including satellite images, geological data, and historical records of landslides. This study developed a systematic approach to assess the probability of landslides by considering ten (10) influential factors: land use/land cover, slope, aspect, elevation, curvature, lithology, proximity to lineament, and normalized difference vegetation index (NDVI). The ten influential elements were prioritised based on literature review, expert knowledge, and preliminary study area analysis. The aforementioned causal elements are integrated with a comprehensive landslide inventory map. The sensitivity of the study's area to landslides was mapped using a frequency ratio (FR) model. Subsequently, it was classified as representing various degrees of vulnerability, spanning from extremely minimal to quite significant. The effectiveness of the suggested model was measured by evaluating the accuracy of the generated map of landslide susceptibility by the area under the curve (AUC) technique. Based on the most recent study results, the success rate curve has an area under the curve (AUC) of 79.6%, which indicates a highly satisfactory level of performance. Policymakers may utilize the findings of this study to make educated decisions on how to mitigate the risks of landslides in relation to land use and preparedness for disasters.

Pollution potential of dumping sites on surface water quality in Ethiopia using leachate and comprehensive pollution indices.

Municipal solid waste disposed of in illegal dumpsites pollutes the surface and groundwater. However, accurately determining these pollution levels is typically challenging for practitioners and decision-makers in developing countries. The purpose of this study is to use the leachate pollution index (LPI) to assess the contamination potential of uncontrolled dumping sites along the course of the Kulfo River in Arba Minch, Ethiopia. The comprehensive pollution index (CPI) approach was also utilized to assess the suitability of Kulfo River water quality for aquatic species. Leachate samples were collected from four uncontrolled dumping sites along the Kulfo River's course and analyzed for fifteen leachate characteristics necessary to quantify the LPI sub-indices. Water samples were taken from three monitoring stations along the river and examined for aquatic species suitability. When the leachate parameters were compared to the Indian limit for discharge of treated leachate, it was found that dumping sites posed a considerable risk of pollution to adjacent water resources. The overall LPI ranged from 23.34 to 27.35, which is higher than the discharge standard LPI of 5.69, indicating that dumping sites can threaten the surrounding water resources and human health. Based on the rating scale of CPI, at all monitoring stations, the river resulted severely polluted. Finally, appropriate strategies to reduce the pollution and the related mismanagement of solid waste were discussed. Combining LPI and CPI methods can represent a crucial tool for experts and decision-makers in developing countries to evaluate the pollution potential of dumping sites and water resource monitoring.

Developing a DEM and Elucidating through SWAT to Conserve Soil in Kulfo Watershed of Rift Valley Basin, Ethiopia

Due to uninterrupted erosion and transportation, huge volume of sediments carried away by streams and rivers are finally deposited on the meanders, lakes, and reservoirs when the velocity of the surface water flow decreases. Kulfo River in the southern part of Ethiopia faces a challenge due to massive deposit of sediments. Hydrometeorological and spatial data of Kulfo watershed from the observed stream flow data series near Kulfo bridge and four meteorological station data were used to assess the depositional environment of Kulfo watershed. The data length covers the period from 2000 to 2019. Geomorphic parameters of the watershed were developed by using a 30m × 30m digital elevation model (DEM). The spatial distribution of sediment yield of the study area was estimated using SWAT, the soil and water assessment tool. Scenarios were developed to assess the effectiveness of watershed management interventions provided at the watershed and critical subwatershed level. The model genuinely replicated the observed discharge and sediment with an overall performance of 0.75 as measured by NSE. Twenty-one subbasins were created, and the observed average sediment yield was calculated as 11.9 ton/ha/y. The observed average sediment yield reduction at the hotspot subwatershed level postapplication of contouring, filter strip, terracing, and strip cropping were 40.79%, 57.94%, 66.02%, and 62.93%, respectively. By intricately analyzing, it can be referred that terracing is the best conservation measure to be incorporated into the affected subbasins.

Remote sensing, GIS, and RUSLE in soil loss estimation in the Kulfo river catchment, Rift valley, Southern Ethiopia

Quantification of soil is crucial for maximizing the advantages of land resources while minimizing the negative consequences of land degradation in the long term. It will also make it possible to identify locations that need immediate soil erosion management. The present study was carried out in the Kulfo river catchment, Rift valley, Southern Ethiopia. The Revised Universal Soil Loss Equation (RUSLE) method was utilized to estimate the mean yearly soil loss in the research region using remote sensing, other collateral data. The RUSLE model inputs were mapped and integrated into the ArcGIS software, and the results show that 0 and 1211 t ha−1year−1 are the minima and maximum soil loss in the present study area. Soil erosion-prone regions were divided into three categories: 0-42 t ha−1year−1 (low), 43-128 t ha−1 year−1 (medium), and > 128 t ha−1 year−1 (high). And the average rate of soil erosion is 68.47 t ha−1year−1. Low, medium, and high soil erosion areal extent and area percentages in the current research area is 270 km2 (77 %), 61 km2 (17 %), and 19 km2 (6%), respectively. A high rate of soil erosion was found where high steep slope, barren land, and high precipitation occurred in the present study area. The current study's outcomes were confirmed by comparing soil loss estimates in the same geo-environmental conditions found in Ethiopia's highlands. The outcome of this study is important for decision-makers and policymakers.

Computing the sediment and ensuing its erosive activities using HEC-RAS to surmise the flooding in Kulfo River in Southern Ethiopia

Purpose The change in sediment transport phenomenon and morphological characteristics of Kulfo River in the southern part of Ethiopia is estimated using one-dimensional hydraulic modelling. The purpose of this study is to predict erosion and sedimentation using hydrological engineering center-river analysis system (HEC-RAS) model. Design/methodology/approach Geometrical survey data of 2005 and 2019 were used to assess the impact of flood depth with 100 years of return per period on the morphology of the river. The bed and bank materials at selected sites of the river were sampled to estimate the grain size using manning roughness coefficient. Discharge and suspended sediment concentration were sampled thrice per day for a stretch of three months to develop a rating curve. Findings HEC-RAS model indicates that flood depth with 100 years return period had a significant inundated area during 2019 in comparison to 2005 demonstrating a temporary change in the morphology of the river. Acker and White method in HEC-RAS was used extensively to calculate the sediment load and subsequently calibrated. In the upper reach of the study area, there was aggradation and degradation, whereas the only degradation was noted in the middle to the downstream reach of the channel. Seasonal flood during peak flow due to a rise in bed level is most prevalent during the aggradation period. Originality/value Comparison of a flood depth inundating the catchment and sediment deposition has been intricately analyzed by using HEC-RAS model.

Heavy metal concentration in vegetables and their potential risk for human health

This study assesses heavy metal levels in the water, soil, and vegetables (swiss chard, lettuce, cabbage, collard green, tomato, green pepper, and carrot) irrigated with wastewater in Gamo, Ethiopia. The samples of soils, waters, and vegetables were randomly collected, processed, and analyzed for heavy metals using atomic absorption spectroscopy. The results obtained show that the mean concentrations of Cd, Cr, and Ni had the highest concentration, and Pb, Zn, and Cu had the lowest concentration in irrigation waters. The levels of Cd in the Kulfo river area and Chamo Lake area and Cu in most of the farm soils were also found to be higher than the guideline values. The study also revealed that the mean levels of Cd in most vegetables and Cr and Pb in some vegetables were higher than the maximum recommended limits set by the World Health Organization / Food and Agriculture Organization 2001. Among the vegetables, cabbage had the highest heavy metal content followed by Swiss-chard, carrot, tomato, collard green, green pepper, and lettuce. The Hazard quotient of Cu, and Ni of all samples of vegetables and Cd in some samples vegetables obtained exceeded unity. It signifies that there are potential health risks to the consumers. This study recommends regular monitoring of heavy metals in soils, waters, and foodstuffs to prevent excessive accrual in the food chain.

Концентрация тяжелых металлов в овощах с ирригационных полей, использующих сточные воды, и потенциальный риск здоровью населения

This study assesses heavy metal levels in the water, soil, and vegetables (swiss chard, lettuce, cabbage, collard green, tomato, green pepper, and carrot) irrigated with wastewater in Gamo, Ethiopia. The samples of soils, waters, and vegetables were randomly collected, processed, and analyzed for heavy metals using atomic absorption spectroscopy. The results obtained show that the mean concentrations of Cd, Cr, and Ni had the highest concentration, and Pb, Zn, and Cu had the lowest concentration in irrigation waters. The levels of Cd in the Kulfo river area and Chamo Lake area and Cu in most of the farm soils were also found to be higher than the guideline values. The study also revealed that the mean levels of Cd in most vegetables and Cr and Pb in some vegetables were higher than the maximum recommended limits set by the World Health Organization / Food and Agriculture Organization 2001. Among the vegetables, cabbage had the highest heavy metal content followed by Swiss-chard, carrot, tomato, collard green, green pepper, and lettuce. The Hazard quotient of Cu, and Ni of all samples of vegetables and Cd in some samples vegetables obtained exceeded unity. It signifies that there are potential health risks to the consumers. This study recommends regular monitoring of heavy metals in soils, waters, and foodstuffs to prevent excessive accrual in the food chain.

Application of hydrodynamic models for designing structural measures for river flood mitigation: the case of Kulfo River in southern Ethiopia

Flood is one of life-threatening events in different parts of Ethiopia. The causes of flood might vary from place to place, for instance, rates of deforestation, agricultural expansion, urbanization, wetland drainage, climate change, siltation of river bed, and several other types of land use change might be the cause for flood in different rivers banks. This study aims to assess, investigate, and design suitable river training works on lower Kulfo river reach. The study reach has been seriously affected by extreme floods due to the above reasons. For minimizing the loss due to flood, and to use the advantage of flood for different developmental activities various flood control measures should be adopted. The flood control measures which should more correctly be termed as “flood management” can be planed either through structural engineering measures or non-structural measures. Structural measures comprise retarding structures which store flood water, channel improvements which increase flood-carrying capacity of the river, embankments, and levees which keep the waterway from flood-prone area, detention basin which retards and absorbs most of the floodwater. Within the identified 6 km reach, field investigation including secondary data collection has been done to predict the flood extent using 1D hydrodynamic model, HECRAS and HEC Geo RAS. Estimated flood depth and extent helped us in fixing the dimension of different river training structures selected. The modelling result indicates a maximum channel bed flood depth of 4.3 m and flood plain flood depth 2.3 m obtained using a 100-year return flow. Analysis of soil samples indicates that the lower reach of Kulfo river is gravel and sand dominated meandering river, with estimated scour depth up to 3.41 m along the river course. Levees have been designed in conjunction with Groynes to protect the Upstream farm located at the prison and upper part of the Limat households. Frequent floods happening near both bridges shall be reduced by using Guide banks without influencing the bridges and diversion structures. Consideration is given for the ecosystem to stay in equilibrium, by providing suitable outer slopes so that plantation is possible on the top and side slope of the levees and guide banks.

Characteristics of hydrological extremes in Kulfo River of Southern Ethiopian Rift Valley Basin

Hydrological extreme events such as floods and drought are common in Ethiopia which eventually causes environmental hazards. Kulfo River is one of Southern Ethiopian Rift Valley Basin that has experienced flooding for years. Therefore, this study aimed characteristics of hydrological extremes (1985–2014) in the Kulfo River, which is important for effective drought and flood monitoring and early warning systems. The hydrological drought was assessed using the streamflow drought index (SDI). Flood frequency distribution (FFD) software package was deployed to determine the flood frequency curve of the Kulfo River. The goodness-of-fit test results showed that the Generalized Extreme Values (GEV) distribution was found the best-fit probability distribution model in the Kulfo River, while the results of SDI values showed that extreme drought events were observed in 1991, 1992, and 2014 with magnitudes ranging from − 2.04 to − 2.7, − 2.0 to − 2.3, and − 2.10 to − 2.24, respectively, which cause reduction of lake level, lowing of groundwater level, and decreased the amount of river flow. SDI value indicated 6-year drought duration has occurred with the relative frequency of 20% in the 3- and 6-month timescales. The flood frequency results show the lowest probability of having flood magnitude has affected the river morphology. The study provides valuable information for policy and decision makers to implement different adaptation and mitigation measures for extreme hydrological events in the Kulfo River.

Mapping of soil erosion-prone sub-watersheds through drainage morphometric analysis and weighted sum approach: a case study of the Kulfo River basin, Rift valley, Arba Minch, Southern Ethiopia

In the present study, soil erosion prioritization of sub-watersheds of the Kulfo River basin was conducted by adopting a drainage morphometric analysis along with a statistical correlation matrix-based weighted sum approach. The drainage network extracted and sub-watershed boundaries were demarcated through GIS techniques using advanced space-borne thermal emission and reflection–digital elevation model (ASTER–DEM). The Kulfo River basin was separated into six sub-watersheds (SW-1 to SW-6), and different morphometric criteria were calculated using the standard formula. And, morphometric parameters like drainage frequency, bifurcation ratio, drainage density, form factor, circulatory ratio, drainage texture, elongation ratio, compact coefficient, and length of overland flow have been considered for sub-watershed prioritization. Based on the results, the Kulfo River basin’s sub-watersheds were categorized into five priority classes: very low, low, medium, high, and very high. The results illustrate the sub-watersheds (SW-1, SW-2, SW-3, and SW-6) that approximately 65% of the Kulfo River basin’s total area fall under the very high, high, and medium soil erosion-prone areas, respectively. Therefore, the above-mentioned four sub-watersheds can be a value for the consideration of the soil protection plan. The outcomes derived from this study will be valuable information for several partners like agriculturists, surface and groundwater wealth administrators, and decision-makers for improving the soil management process. The current research shows that ASTER–DEM data, GIS approach, and a statistical correlation matrix-based weighted sum approach are vibrant tools for watershed prioritization in data-scarce regions.

Local Scour at Bridge Piers: the Case of Failure of Kulfo River Bridge at Arba Minch, Southern Ethiopia

The scouring of the streambed around bridge piers can be caused by the characteristics of the stream itself, due to the contraction of the flow by the bridge crossing and/or due to other human interference upstream and downstream of the crossing. Kulfo River Bridge failure in October 1997 due to excessive scour under one of the piers after a flood event is one typical case. It was known that excessive sand/gravel was being extracted for construction purposes prior to the failure. To determine the extent and specific cause of the failure, river survey, bed material sampling and simulation of the pier scour under different river bed scour scenarios were conducted. From the bed material sampling, the grain size was found to vary from very fine sand to small cobbles, showing that the bed is in the coarse-grained class – gravel bed alluvial river. Simulation of the pier scour was done using BRI-STARS (Bridge Stream Tube Model for Alluvial River Simulation) model. The model was calibrated in two phases: (i) calibration of hydraulic parameters, and (ii) calibration of sediment transport parameters.Measured water surface elevations and Manning’s roughness coefficient were used as calibration parameters. Among the two gravel/sand mining scenarios (wet-pit mining from the active channel, and bar skimming or scalping above low water level) simulated, the wet-pit mining resulted in maximum scour under the bridge pier when it is followed by a 100-year flood and consequent failure. This result shows that sand/gravel extraction operations within or near the streambed have direct impact on the stream morphology and river structures.

Predicting the Impact of Climate Change on Kulfo River Flow

Assessment of the potential impact of climate change on hydrology and water resources of rivers is important for future planning and management of water resources. The objective of this paper is to predict the impact of climate change on stream flow of Kulfo River. This study used Soil and Water Assessment Tool (SWAT) model and hypothetical climate change scenarios based on the fifth assessment report of Intergovernmental Panel on Climate Change (IPCC) and by review different research papers on climate change to investigate the current and two future scenarios 2050s and 2080s stream flow magnitude in the River. The SWAT mode was calibrated and Validated against stream flow and attained coefficient of determination 0.81 and 0.92, and Nash Sutcliffe Efficient of 0.68 and 0.78 during calibration and validation respectively. The hypothetical climate scenarios were compared to the observed baseline period (1987-2014) and the potential impact of climate change on stream flow quantified as, the average annual stream flow of Kulfo River is projected to increase by 5.42%, in 2050s. In contrast it was found to give the maximum decrease in discharge by -8.2% in 2080s. Increasing temperature by 0.5°C decreased stream flow rates by 2.99% in 2050s while 10% drops in rainfall resulted in a stream flow reduction by 5.28% in 2080s. Overall, the results show that stream flow in the Kulfo River will be more sensitive to change in precipitation than change in temperature.

Multivariate Rainfall - Runoff Modeling of Kulfo River

Multivariate Rainfall - Runoff Modeling of Kulfo River

English

Irrigation is a common agricultural practice for farmers in the periphery of flowing rivers in Ethiopia. In the south west Ethiopia, fruits and vegetables are majorly produced under irrigation where the mode of irrigation is by pumping water from flowing rivers. Irrigated agriculture has only been linked to the availability of water in physical terms, while the quality of water is significantly important for sustainable agricultural production. A study was conducted to assess the water quality parameter of the Kulfo River in South West part of Ethiopia. Accordingly, the concentration of calcium cation (21 g/L) is the highest concentrated followed by sodium (8.3 g/L), magnesium (5 g/L) and potassium (1.8 g/L) is the least concentrated in the Kulfo River. The concentration level of the chloride ion has significantly (25 mg/L) increased from what it was reported (3 to 12 mg/L) in 2004. More importantly, both the electrical conductivity and the sodium adsorption ration are relatively low, implicating the water is non saline and can safely be used for irrigation. Key words: Electrical conductivity, irrigation water, pumping, sodium absorption ratio, river.

Techno-Economic Feasibility of Small Scale Hydropower in Ethiopia: The Case of the Kulfo River, in Southern Ethiopia

This paper presents the technical and economic feasibility of grid connected small scale hydropower construction in selected site of the Kulfo River in southern Ethiopia. In doing so the paper presents the general overview of Ethiopia electric power situation; small scale hydropower situation and barriers and drivers for its development; site assessment and cost estimation methods and at the end presents techno-economic analysis of small scale hydropower development on the Kulfo River in southern Ethiopia. The technical and economic feasibility of the site have been studied by using HOMER, RETscreen, and SMART Mini-IDRO software. The result of simulation shows that the construction of small scale hydropower in the Kulfo River is technically and economically feasible with total net present cost of$13,345,150, cost of energy$0.028/kWh, simple payback period of 12.4 year, and internal rate of return 12.9%. The result also shows that construction of hydropower curtails greenhouse gas emissions such as carbon dioxide by 96,685,45 kg/year, sulfur dioxide by 4,1917 kg/year, and nitrogen dioxide by 20,500 kg/year.

Time series modeling and forecast of river flow

Changing climate, human interventions to natural water flow pattern, haphazard urbanization etc., are the reasons for intense flood even after development of so many structural measures of overflow control. Kulfo River basin is situated in relatively dry southern area of the Ethiopia and is still under geographical modification with hilly topography and impervious soil texture. The concern of the present research is to simulate flood episode in order to develop flood management strategies to reduce disaster. The complexicity of natural hydrological phenomenon and dependent random variables can be better expressed considering it as stochastic process. Flood (maximum river flow) forecasting on the Kulfo River with monthly runoff data using stochastic ARIMA, Time Series model was developed for warning purposes. The analysis of seasonally varying time series of discharge data has revealed that a higher order ARIMA model may produce excellent results for three to six months forecast.

Cytotaxonomy of Simulium soderense sp. nov. and a redescription of the ‘Kulfo’ form (Dunbar, 1969) of Simulium damnosum s.l. (Diptera: Simuliidae) as Simulium kulfoense sp. nov. in Ethiopia

The exact taxonomic identity of members of the Simulium damnosum Theobald complex in Ethiopia was not known until recently. A cytotaxonomic analysis of larval chromosomes from the Kulfo River area in southern Ethiopia, from where the ‘Kulfo’ form was reported, and from the Awash River at Sodere in central Ethiopia has revealed the existence of two newly recognized species, namely Simulium kulfoense and Simulium soderense. Although three fixed and 11 floating inversions in the chromosomes of the ‘Kulfo’ form were described in an idiogram, in the present study four fixed and 17 floating inversions were observed, out of which only seven floating inversions were the same as Dunbar's, indicating that the remaining 10 inversions were either missed or misinterpreted. Though both species share many inversions, S. kulfoense sp. nov. has a diagnostic inversion on chromosome II, IIL-E6, with no sex-linked chromosomal arrangement, while S. soderense sp. nov. has a sex-linked inversion, IIS-3, which warrants it as a distinct species. Both of these new species also share many inversions with the recently described new species from south-western Ethiopia, Simulium kaffaense, including the fixed inversions IIL-E1 and E3. Since both the study sites are known to be free of onchocerciasis, and the flies are not anthropophilic, both the species are not presumed to be vectors of human onchocerciasis. The presence of IS-1 and a complex inversion possibly involving IL-3 strongly indicates that the two species belong to the ‘Nile’ phylogenetic group of S. damnosum s.l.