Civil and Water Engineering
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- ItemA flux-correct Green element model of quasi three-dimensional multiaquifer flow.(American Geophysical Union, 2000-12) Taigbenu, A.E.; Onyejekwe, Okey O.Transient flow in multiply layered aquifers, separated by connecting layers of aquitards which provide hydraulic interactions between the aquifers, is solved by the Green element method (GEM) in a manner that reveals one of its strengths of being able to correctly model the leakage flux without resorting to adjusting the grid representing the one-dimensional (l-D) flow in the aquitards, as done in the finite element method (FEM). The hydraulic approach of approximating the flow is adopted so that flow in the aquifer takes place in two dimensions and that in the aquitards takes place in the one-dimensional vertical direction. The 1-D Green element (GE) model earlier developed for transient diffusion and referred to as the transient GE (TGE) formulation [Taigbenu and Onyejekwe, 1999] is used in modeling the flow in the aquitards, while the 2-D GE model developed for linear and nonlinear transient diffusion [Taigbenu and Onyejekwe, 1998] is used for calculating the flows in the confined and unconfined aquifers. Both models are coupled to solve regional flow problems in multiaquifer systems of arbitrary geometry which receive point and distributed recharge of arbitrary strengths. The solution procedure, which is iterative, provides information on the hydraulic heads and fluxes in the aquifers and aquitards at various specified times. Because GEM is founded on the singular integral theory, singularities that arise from water abstractions at wells (point recharge) are naturally captured in the singular Green's function, thereby making it possible to use a more coarse grid for problems in which there exist active wells. Furthermore, the implementation procedure of GEM achieves sparsity of the coefficient matrix so that less amount of computing resources is required for its decomposition. The superiority of the current approach over FEM in predicting the leakage flux through the aquitards and achieving comparable accuracy for well problems with coarser grid is demonstrated
- ItemImpacts of Solid Waste Management Practices on Environment and Public Health: A Case of Bahawalpur City, Pakistan(2016) Mohsin, M.; Chinyama, A.Safe and secure disposal of solid waste is now becoming a major issue for most of developing countries with accelerating urbanization and increasing pressure of populations. A study was conducted in Bahawalpur City; Pakistan. The main objective of the study was to investigate the sources and impacts of solid waste management practices on the surrounding environment and public health. This was achieved by specifically identifying the sources and types of solid waste in the city by identifying the different solid waste management practices and their impacts on the environment and human health. Data about solid waste generation, collection, disposal and their impacts on human health and environment was collected in Model Town C using a structured questionnaire from 80 randomly sampled respondents as well as by field observations. Secondary data from institutional records was also collected. Statistical analysis in the form of descriptive statistics and chi-square test were applied to the data. It was found that the environment in study area was highly polluted with open dumping of solid waste in open spaces and vacant plots. Households contributed the most solid waste generation and open dumping. The solid waste generated at household level consisted of organic waste, plastics and polythene bags. Institutionally, Tehsil Municipal Administration (TMA) and later Bahawalpur Waste Management Company (BWMC) were found to be responsible for solid waste management in the city but the overall situation is not satisfactory. The impacts of poor solid waste management practices were found to be: land degradation, creation of breeding grounds for disease carrying vectors such as mosquitoes, rats, rodents, decrease in land values; and different severe diseases. Furthermore, it was found by statistical analysis, that there was a significant relationship between the poor solid waste management practices and environmental and health problems faced by the community
- ItemPerformance Based Water Loss Management for Gweru, Zimbabwe(2017) Makaya, E.Different water utilities use different performance indicators to assess their performance. Although these indicators are peculiar to particular situations, it is paramount that each indicator is applied consistently among utilities as this is good for benchmarking purposes. Besides being well documented, performance indicators have not been well reviewed from the perspective of developing countries. Furthermore, there is limited understanding of the application of performance indicators among developing countries. Therefore this paper reviewed performance indicators for physical water loss management. The African Development Bank self-assessment matrix was applied to the City of Gweru, Zimbabwe. Furthermore, the infrastructure leakage index was used to assess the performance of the water utility. The self-assessment approach showed a 62% level of implementation of NRW strategies by the city. This means that the city was poorly managing its non-revenue water. The city had an infrastructure leakage index of 9.7. This index is in Category C of the International Water Association physical loss matrix meaning that the city was managing its non-revenue water poorly. Therefore the city must be proactive in the management of its physical water losses as well as maintain its infrastructure consistently.
- ItemPredictive Leakage Estimation using the Cumulative Minimum Night Flow Approach(2017) Makaya, ESeveral methods have been used in estimating leakages. Although the minimum night flow analysis method has been widely used in leakage estimation, the cumulative minimum night flow method is one method that can yield comparatively good leakage estimates. This paper applies the cumulative minimum night flow method to estimate water leakage in a water distribution system. The cumulative minimum night flow method develops a model from empirical night flows which is used to estimate mean minimum night flows and hence estimate leakages. The result was compared with the South Africa minimum night flow analysis methodology. It was found out that the model developed from the cumulative minimum night flow method yielded good result, (R2 =0.9998). Thus, the cumulative minimum night flow method could be relied on in predicting leakage estimates in water distribution systems. Furthermore, the model could be used in other locations other than that described in this paper.
- ItemPrevalence of Persistent Organic Pollutants in Blantyre - Malawi(2017) Makaya, E; Tanyanyiwa, VThe industrial and agricultural revolutions have led to the development of a variety of chemicals ranging from insecticides, pesticides, fungicides and bactericides. However the demand for these chemicals led the manufacturers to manufacture the chemicals without considering the sustainability of using such chemicals. During the last half of the 20th century, the global environment has become contaminated with a number of persistent and fat-soluble chemical contaminants, commonly referred to as the Persistent Organic Pollutants (POPs). These compounds generally have low water solubility, do not degrade readily in the environment, bio-accumulate in food chains, and have been linked to adverse health effects in both humans and wildlife. In order to develop appropriate strategies and institutional responses, it is pertinent to assess the prevalence of the variety of organic pollutants and the people’s understanding and awareness of POPs that pose a threat to the biophysical aspect of the environment, if used or disposed of in unsupervised means. Thus, this study sought to assess the inventory of POPs, level of awareness and measures used in dealing with the chemicals in Blantyre, Malawi. The researchers used a qualitative research design. The research instruments used were a questionnaire, key-informant interviews and observations. The study focused on Ndirande peri-urban area comprising Mulanje, Thyolo, Zomba, Chiradzulu and Njuli. A random sample of sixty-four respondents was selected and a total of 64 questionnaires administered. The survey covered 5 sites that included markets, agro-dealers, hardware shops, estates and chemical companies. Descriptive statistics were obtained from key- informant interviews and observations. Findings revealed that despite the banning of POPs in Malawi as a signatory to the Stockholm Convention of 2001, the illegal usage and selling of banned POPs was rampant with hardware shops, agro-dealers and vendors. The survey also revealed low level of awareness and knowledge about POPs pesticides especially among the general public in Ndirande Peri-urban. There was presence of Chlordane as the most common pesticide used to control termites and was mainly sourced by the local farmers from the market vendors, hardware shops and Agro-dealers. The pesticide DDT was identified as resurfacing with its source into the country linked to Mozambican traders. The majority of the farmers cited DDT as the main pesticide used to control termites and protect crops such as maize after harvest. In addition the survey revealed the presence of a power utility with a number of obsolete transformers suspected to be contaminated with PCBs still waiting to be disposed for incineration at Blantyre West Sub-station. The researchers observed that this placed at high risk the workers at the power utility of PCBs due to lack of adequate protective wear. It was observed that children were mainly exposed through improperly disposed obsolete pesticides, insecticides and chemical containers. The study concluded that there is need for education of people to ensure their awareness of the dangers associated with the illegal pesticides usage. Integrated Pest Management was recommended as the best alternative approach in peri-urban agriculture
- ItemResearch Funding Needs for African Engineers: Challenges and Perceptions(2017) Makaya, E.Africa and sub-Saharan Africa in particular, with the exception of South Africa, have lately lagged behind in postgraduate research, an issue attributed to lack of research funding for engineering sciences. This paper investigated the funding needs of engineering sciences in Africa. Specifically, it established the funding needs of African engineering sciences, factors affecting higher learning institutions in securing research funding and assessed the prevalent engineering research needs for Africa. Key informants to this paper were postdoctoral candidates drawn from Cameroon, Ethiopia, Ivory Coast, Kenya, Nigeria, Tanzania, Uganda and Zimbabwe. Through a questionnaire survey, the study found out that Africa has the capacity to carry out high profile engineering researches but the funding needs are not fully met resulting in frustration, whose ripple effects culminate in brain drain. Institutional frameworks in many African countries have been found not favouring engineering sciences. Although efforts are being made, as evidenced by increase in scientific publications, the growth of Engineering Sciences lags behind other disciplines. Thus, the international community of research funders should forge partnerships and collaborations with engineering institutions in Africa for availing and putting to good use research funding.
- ItemA time-dependent Green’s function-based model for stream-unconfined aquifer flows(Water research commision, 2004-07-01) Taigbenu, A.E.A numerical formulation that is based on the Green element method (GEM), which incorporates a time-dependent Green’s function, is used to solve transient two-dimensional flows of stream-unconfined aquifer interaction. The Green’s function comes from the fundamental solution to the linear diffusion differential operator in two spatial dimensions. In classical boundary element applications, this Green’s function has found use primarily in linear heat transfer and flow problems; its use here for the nonlinear stream-unconfined aquifer flow problem represents the computational flexibility that is achieved with a Green element sense of implementing the singular integral theory. The nonlinear discretised element equations obtained from numerical calculations are linearised by the Picard and Newton-Raphson methods, while the global coefficient matrix, which is banded and sparse, is readily amenable to matrix solution routines. Using four numerical examples, the accuracy of the current formulation is assessed as against an earlier one that incorporates the Logarithmic fundamental solution. It is observed that comparable accuracy is achieved between both formulations, indicating that the current formulation is a viable numerical solution strategy for the stream-aquifer flow problem.
- ItemUnderstanding the Poor Performance of Urban Sewerage Systems:A Case of Coldstream High Density Suburbs, Chinhoyi, Zimbabwe(UPDR, 2013-09) Chinyama, Annatoria; Toma, TendaiThe population of Coldstream High Density Suburbs in Chinhoyi, Zimbabwe is increasing and the sewerage system shows signs of poor performance. The frequency of reported sewerage system blockages in the suburb increased from 43 per month to 65 per month between April 2012 and March 2013. The suburb has also been experiencing water shortages. An increasing population and low water supply versus overflowing sewage is a potential health risk. The main objective of this paper was to investigate the causes of the sewer system poor performance. This was achieved by assessing the sewer system infrastructure as well as the operation of the system. The impact of the behaviour of residents on the performance of the system was also discussed. The main components of the infrastructure (manholes and sewers) were physically checked for soundness. The operation of the system was assessed by a hydraulic analysis of discharge, depth of flow and velocity of flow in the sewers. Questionnaires were used to investigate the impact of the behaviour of residents on the performance of the sewer system. It was found that 4% of the components of the sewer system infrastructure were below standard and the collector main sewer was the one mainly affected. 68% of the sewers along the collector main had velocity of flow below 0.6m/s and all the sewers had depth of flow below 50%. Of the residents interviewed, 90% dumped solid wastes in the sewers and 43% did so because they were unaware of the impact. It was concluded that the sewer system failed to meet standard because the sewer system fails to self-cleanse the solid waste dumped by residents in the sewers due to water shortages. It is recommended that the municipality raises awareness among residents and some of the infrastructure should be rehabilitated.
- ItemWater governance challenges in rural South Africa: exploring institutional coordination in drought management(2020) Makayaa, E.; Rohseb, M.; Dayc, R.; Vogeld, C.; Mehtae, L.; McEwenf, L.; Rangecroftg, S.; Van Loonh, A.F.Droughts have severe direct impacts on the livelihoods of rural populations. Thus, the management of water for communal agriculture and water supply should be well coordinated to enhance drought resilience. Notwithstanding the interrelations among water management institutions in South Africa, there are complexities in the way these institutions work together, both in preparation for, and during drought times. In this article, we examine the governance of water resources in South Africa with a view to understanding institutional coordination in drought management at different operational scales. Using a qualitative approach, the roles and relationships between water actors at the local and regional level were analyzed for their adequacy in building local level drought resilience in a village in the Limpopo province, South Africa. Key informant interviews conducted revealed operational drought management challenges that emanate from communication barriers, coordination inconsistencies, and undefined, unclear actor roles and responsibilities during disasters. The top-down approach to disaster management, while of some value, currently constrains the effectiveness of the local-level institutions implementing local drought risk reduction efforts. Achieving more successful water and drought governance endeavors could be enhanced by greater and wider engagement with community-based actors and water management institutions.