Rwanda Journal of Engineering, Science, Technology and Environment <p>The <em>Rwanda Journal of Engineering, Science, Technology and Environment</em> (RJESTE) is a peer-reviewed journal published bi-annually by the University of Rwanda - College of Science and Technology. The journal aims at publishing original research articles, review articles, and selected conference articles on the latest developments in the fields of engineering, science, technology, environment and related. The publications should either demonstrate a significant new discovery or other contribution that has been established to fairly rigorous scientific standards. The Journal will publish articles written in standard British English.</p> University of Rwanda, College of Science and Technology en-US Rwanda Journal of Engineering, Science, Technology and Environment 2617-2321 <span lang="EN-GB">The copyright for articles published in this journal is owned by the journal.</span> On-site and Off-site Effects of Soil Erosion: Causal Analysis and Remedial Measures in Agricultural Land - a Review <p>Soil erosion is one of the main factors causing land degradation. Furthermore, loss of soil nutrients ultimately causes worldwide reduction of agricultural productivity and water quality deterioration. Therefore, soil erosion control measures are required as an aspect of catchment management. The general purpose of this paper review is to make an overview of soil erosion throughout the world in order to highlight required studies on which to be based when proposing appropriate erosion control measures for agricultural fields. Different scientific documents including journal articles, internet materials, conference papers and books were used as research materials to achieve the objectives of the present work. This methodology enabled the researcher to make a synthesis of various researchers’ views on this topic. Principally, this review focused on the effects and remedial measures of soil erosion. The research findings highlighted that soil erosion affects greatly the agricultural land, human properties and aquatic ecosystem. Both on-site and off-site effects are analyzed. Sediment transport in rivers resulted from soil erosion impacts on bridges, hydropower plants, water treatment plants and water bodies such as lakes and water reservoirs. The present review article strongly recommends the followings: (1) Performance improvement of the existing erosion control measures; (2) Promotion of new soil erosion adaptive measures; (3) Farmers trainings on Best Management Practices of soil erosion control and (4) Sensitization of governmental institutions and Non-governmental organizations (NGOs) to be extensively involved in soil erosion management.</p> <p><strong>Keywords</strong>: Erosion causes, erosion effects, erosion control measures</p> Félicien Majoro Umaru Garba Wali Omar Munyaneza François-Xavier Naramabuye Concilie Mukamwambali Copyright (c) 2020-07-14 2020-07-14 3 2 10.4314/rjeste.v3i2.1 Assessment and Prevention Strategies of Soil Surface Crusting Caused by Rainfall Events: Case Study of Sebeya Catchment Agricultural Land in Rwanda <p>The history of soil erosion is an integral part of the agriculture. All over the world, wherever human being started the agricultural operations, there exists the problem of soil erosion in some extent. Soil erosion leads to the reduction of water infiltration rate and enhances runoff and soil degradation. This study focuses on Sebeya catchment located in the Western part of Rwanda. The main objective of this study was to assess various preventive measures against soil surface crusting and development of runoff coefficients in order to minimize the soil loss in Sebeya catchment agricultural fields. The proposed methodology was much concerned with the efficiency analysis of soil conservation practice of mulching in maize cover crops. The names of the three experimental field plots sited are Maize-Fertilizer-Mulching (MFM), Maize-Fertilizer (MF) and Bare Soil (BS) which were set in Rugerero Sector of Rubavu District. Each of these 3 plots was constructed with its runoff collecting tank and they were under similar conditions except land cover. Samples of soil from field plots and water from runoff collecting tanks were tested for soil classification and soil loss estimation from each plot respectively. The analysis of results showed that soil of the experimental plots is a gravelly sand with (sand:56.27%; clay and silt: 3.24% and gravel: 40.49%). Also, the results showed that the plot coded as MFM, has high moisture content with low runoff and soil loss compared to 2 other plots. This research revealed that soil conservation practices such as surface mulching and vegetative cover reduce runoff, soil loss and are well recommended for preventing and controlling soil surface crusting.</p> <p><strong>Keywords:</strong> Soil erosion, mulching, soil crusting, field experiments, Rwanda</p> Félicien Majoro Umaru Garba Wali Omar Munyaneza François-Xavier Naramabuye Concilie Mukamwambali Copyright (c) 2020-07-14 2020-07-14 3 2 10.4314/rjeste.v3i2.2 Heavy Metal Concentrations in Water Samples from Lake Kivu, Rwanda <p>Heavy metals are among the pollutants threatening the living organisms including human beings. The presence of heavy metals in water is of great concern due to their toxicity to aquatic organisms, humans and ability to accumulate in food chains. Thus, there is a need to regularly monitor heavy metal levels in aquatic medium. The present study was conducted to assess heavy metal concentrations in Lake Kivu water. Water samples from Lake Kivu were taken from three sites, namely: Rusizi, Karongi and Rubavu. Heavy metals in the samples were analyzed using Atomic Absorption spectro-photometer (SHIMADZU AAS-6800) and Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES).Copper, lead, cadmium, chromium, manganese, mercury and arsenic concentrations were determined. Copper ranged from 3.24 to 10.01 μg/l, lead varied from 8.81 to 37.44 μg/l, cadmium ranged from 5.01 to 14.01 μg/l,chromium was between 139.5 and 226.6 μg/l, manganese varied from 598.3 to 795.7 μg/l, mercury ranged from 0 to 0.047 μg/l, while arsenic was not detected in any of the analyzed water samples. Except for arsenic, all the other heavy metals exceeded the EPA (US Environment Protection Agency) maximum permissible limit for class III surface water intended for fish consumption and recreation. Thus, there is a need to establish the sources of lake water pollution by heavy metals in order to design further strategies limiting the amounts of heavy metals entering Lake Kivu.</p> <p><strong>Keywords</strong>: Cadmium, chromium, copper, lead, manganese, mercury</p> Antoine Nsabimana Valens Habimana Gaidashova Svetlana Copyright (c) 2020-07-14 2020-07-14 3 2 10.4314/rjeste.v3i2.3 Performance Assessment of Erosion Remediation Measures and Proposal of The Best Management Practices for Erosion Control in Sebeya Catchment, Rwanda <p>Soil erosion is an environmental concern that affects agriculture, wildlife and water bodies. Soil erosion can be avoided by maintaining a protective cover on the soil to create a barrier to the erosive agent or by modifying the landscape to control runoff amounts and rates. This research is focused on Sebeya catchment located in the Western Province of Rwanda. Sebeya catchment is one of the most affected areas by soil erosion hazards causing loss of crops due to the destruction of agricultural plots or riverbanks, river sedimentation and damages to the existing water treatment and hydropower plants in the downstream part of the river. The aims of this research were to assess the performance of erosion remediation measures and to propose the Best Management Practices (BMPs) for erosion control in Sebeya catchment. Using literature review, site visits, questionnaire and interviews, various erosion control measures were analyzed in terms of performance and suitability. Land slope and soil depth maps were generated using ArcGIS software. The interview results indicated that among the 22 existing soil erosion control measures, about 4.57% of farmers confirmed their existence while 95.43% expressed the need of their implementation in Sebeya catchment. Furthermore, economic constraints were found to be the main limitative factors against the implementation of soil erosion control measures in Sebeya catchment. Also, the majority of farmers suggest trainings and mobilization of a specialized technical team to assist them in implementing soil conservation measures and to generalize the application of fertilizers in the whole catchment. Finally, soil erosion control measures including agro-forestry, terraces, mulching, tree planting, contour bunds, vegetative measures for slopes and buffer zones, check dams, riverbanks stabilization were proposed and recommended to be implemented in Sebeya catchment.</p> <p><strong>Keywords</strong>: Erosion control measures, Sebeya catchment, Rwanda</p> Félicien Majoro Umaru Garba Wali Omar Munyaneza François-Xavier Naramabuye Concilie Mukamwambali Copyright (c) 2020-07-14 2020-07-14 3 2 10.4314/rjeste.v3i2.4 Water Physico-Chemical Characteristics of the Lakes Burera and Ruhondo, Rwanda <p>Rwanda possesses multiple lakes, whose properties were rarely described. The present study assessed physico-chemical characteristics of water in Burera and Ruhondo lakes located in highly populated area with steep slopes, which are under extensive agriculture, thus water quality monitoring is important. Both lakes were alkaline with high content of Mg, while Ruhondo had higher electrical conductivity than Burera. Phosphorus and nitrogen exceeded Class III EPA standards indicating that both lakes are at risk of eutrophication.</p> <p><strong>Keywords:</strong> water quality, lakes Burera and Ruhondo, Rwanda</p> Valens Habimana Antoine Nsabimana Copyright (c) 2020-07-14 2020-07-14 3 2 10.4314/rjeste.v3i2.5 Assessment of Cohesive Soil - Cow Dung Mortar Properties as Replacement of Cement Mortar for Simple Plastering Works <p>The development of local construction industry has resulted in the high demand for cement, used not only for structural but also non structural applications, such as finishing. As a consequence cement has been far from being an affordable material for the good part of the population, especially in the rural areas where financial means are still limited. Regarding the finishing exercise, those people have been using soil mortar alone or reinforced with grasses without any strategy about mixture content. The objective of this study was to assess the performance of cohesive soil mortar mixed with cow dung and establish recommended mix content for plastering works. Twelve samples of soil mortar with 10%, 20%, 30% and 40% of cow dung, were prepared and subjected to drying period of 28 days before they were tested for water absorption, shrinkage, weathering resistance, specific gravity and Atterberg limit tests. The tests showed good results for checked properties with 20% of cow dung, and therefore it could be considered as a low-cost alternative plastering material to cement mortar for some structural members under normal weather conditions. In order to avoid the earlier shrinkage and cracks in this mortar due to spontaneous drying by sun, the mortar should be protected and not be left in open area at earlier stage.</p> <p><strong>Keywords:</strong> Cohesive Soil, Cow dung, Mortar, Shrinkage, Water absorption, Weathering resistance</p> Leopold Mbereyaho Dieudonné Irafasha Etienne Habumugisha Julius Musabirema Copyright (c) 2020-07-14 2020-07-14 3 2 10.4314/rjeste.v3i2.6 In Silico Studies on Structural Function of Melanin Concentrating Hormone Receptor 1 Through Docking Approach, Towards Designing Drug for Treating Obesity <p>Melanin concentrating hormone receptor 1 is a G-protein coupled protein receptor expressed in the lateral hypothalamus and zona incerta, part of the nervous system that regulates feeding behavior and energy homeostasis. It is involved in the stimulation of appetite, this was seen when synthetic MCHR1 or MCH was administered to mice and it resulted in induced obesity due to the enhanced feeding. Many researchers have successfully find out the functions of several proteins, using computational approach. It is in this context that in this study the structural function of melanin concentrating hormone receptor 1 through docking studies has been done to make sure that those who are working to address the problem of obesity while trying to discover the effective drugs gain much insight about this receptor. The <em>in silico</em> methods have been used to predict the model of melanin concentrating hormone receptor 1. The template used for model prediction was human delta opioid receptor with the accession number 4N6H. The predicted model has been evaluated and found to be of good quality. Docking was done to investigate the interaction between the ligand; a bifunctional peptide ‘1-<em>oleoyl-r-glycerol</em>’ and the predicted model of melanin concentrating hormone receptor 1 which showed that fourteen residues interacted between the predicted model and ligand. Among interacting residues, it was realized that some of them are involved in sugar metabolism. Thus this study suggests a potential candidate for drug design against cancer and diabetes.</p> <p><strong>Keywords</strong>: obesity, MCHR-1, docking, structural function, 3D structure, phylogenetic analysis, interacting residues</p> Mutangana Dieudonne Musafili Narcisse Nyurahayo Jean Gaetan Munyampundu Jean Pierre Copyright (c) 2020-07-14 2020-07-14 3 2 10.4314/rjeste.v3i2.7