Engineering & Technology

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Developing a Surface Water - Groundwater Interaction Model for Letaba River System in South Africa
(KATAMBARA, 2006) Katambara, Z.; Ndiritua, J.G.
There is a constant increase in water demand and a pressing need to conserve the environment in the Letaba River system. This is leading to a situation where the demand for water may have outstripped the capacity of the existing resources to sustainably meet them. In the past dams were constructed and boreholes drilled as a strategy of reconciling demand and supply and this is evidenced by the numerous dams and boreholes in the Letaba River system. There are five major dams; three of which have a capacity exceeding 60 million cubic meters and also more than 3000 boreholes in the river basin. Currently, all the dams are stressed and the releases from Tzaneen Dam, intended to meet the water requirements of downstream users including Kruger National Park fail to meet these requirements substantially. Although these demands are high and probably exceed the system’s capacity, it is likely that the reliability of supply can be improved significantly if the surface water - groundwater (sw/gw) interactions within the basin are modelled comprehensively and then incorporated into system operation. This paper reports on an ongoing development of a sw/gw model of the Letaba River System. The model development intends to maximize the use of the relevant available information and data and recognizes the existence of an interaction zone which forms a major link of many of the processes that will be included in the model. It has been found that the scale of monitoring processes in the river system is inadequate and is a significant constraint to the development of the model that is expected to impact on the level of confidence in model implementation and application. Incorporation of uncertainties will therefore be an integral part of the modelling.
Adaptive Iir Filters For Single Interference Suppression In A BPSK DS CDMA System In Rayleigh Fading Channel
(University of Dar es Salaam, 2007-07-01) Mvuma, Aloys N.
In this paper, effect of a single narrow-band interference (NBI) on bit error rate (BER) performance for a binary phase shift keying (BPSK) synchronous direct-sequence code-division multiple access (DS CDMA) communication system operating in a frequency nonselective Rayleigh fading channel is analyzed. Second-order adaptive infinite impulse response (IIR) notch filters with plain gradient algorithm (GA) for suppression of NBI in the DS CDMA system are proposed. A general closed-form BER expression for the DS CDMA system with NBI suppression second order adaptive IIR notch filters is derived based on the standard Gaussian approximation (SGA) method. BER expressions are then derived for the allpass filter-based adaptive IIR notch filter and adaptive IIR notch filter with constrained poles and zeros, the two structures that are commonly found in literature. It is observed that both adaptive IIR notch filter structures exhibit comparable BER performance. Extensive computer simulation results are presented to verify the accuracy and limitations of the analysis.
A Fuzzy Inference System for Modelling Streamflow: Case of Letaba River, South Africa.
(Elsevier, 2008-07-10) Katambara, Zacharia; Ndiritu, John
Stream flow modeling of Letaba River in South Africa is complicated by several factors including the existence of dams and other storage structures whose releases are intermittent and based on rules of thumb depending on the irrigation demands and the need to maintain the flow required in the Kruger National park (KNP). The KNP is located about a hundred kilometers downstream of the main storage and water flows through an alluvial aquifer where complex surface–groundwater interactions occur. Farmers abstract water intermittently along the route directly from the river or indirectly from the alluvial aquifer complicating the flow patterns even more. Consequently, the stream flow series in the river shows very little similarity to what would be considered as natural. The actual abstractions are not measured and only monthly estimates of the abstractions currently exist. Like in many other basins in South Africa, stream flow, groundwater level, rainfall and evaporation data in Letaba is sparse and not very reliable. The Takagi–Sugeno fuzzy inference system using subtractive clustering, an approach which is capable of dealing with vague and inadequate information and data has therefore been used to develop a daily stream flow model for Letaba River. In order to take into account the spatial variability and to maximize the use of the available data, the model is applied in a semi-distributed manner consisting of three river reaches. The shuffled complex evolution (SCE-UA) optimizer has been used to calibrate the model. Six years of data from March 2002 to April 2008 has been used for model calibration and verification. To maximize the Nash-Sutcliffe efficiency, the minimum number of clusters required was found to be 10 for 1000 data points in calibration. An analysis of the location of the cluster centers, the coefficients relating the inputs with the simulated stream flow, and the degrees of membership indicates that no single cluster can be associated to the simulation of a specific hydrologic process or component of the stream flow hydrograph (e.g. high flows or low flows). The fuzzy model does not therefore provide any evidence that it is not a pure black box. The Nash–Sutcliffe efficiency results obtained in calibration and verification showed average values of 0.658 and 0.535 with poor values on the first river reach. Very low percent bias values averaging to _0.4% and _2.7% in calibration and verification are obtained highlighting the model’s potential for applications where mass balance considerations are most important.
An Artificial Neural Network Model of the Crocodile River System for Low Flow Periods.
(Wits, 2009-01-21) Sebusang, Nako M.
With increasing demands on limited water resources and unavailability of suitable dam sites, it is essential that available storage works be carefully planned and efficiently operated to meet the present and future water needs.This research report presents an attempt to: i) use Artificial Neural Networks (ANN) for the simulation of the Crocodile water resource system located in the Mpumalanga province of South Africa and ii) use the model to assess to what extent Kwena dam, the only major dam in the system could meet the required 0.9m3/s cross border flow to Mozambique. The modelling was confined to the low flow periods when the Kwena dam releases are significant. The form of ANN model developed in this study is the standard error backpropagation run on a daily time scale. It is comprised of 32 inputs being four irrigation abstractions at Montrose, Tenbosch, Riverside and Karino; current and average daily rainfall totals for the previous 4 days at the respective rainfall stations; average daily temperature at Karino and Nelspruit; daily releases from Kwena dam; daily streamflow from the tributaries of Kaap, Elands and Sand rivers and the previous day’s flow at Tenbosch. The single output was the current day’s flow at Tenbosch. To investigate the extent to which the 0.9m3/s flow requirement into Mozambique could be met, data from a representative dry year and four release scenarios were used. The scenarios assumed that Kwena dam was 100%, 75%, 50% and 25% full at the beginning of the year. It was found as expected that increasing Kwena releases improved the cross border flows but the improvement in providing the 0.9m3/s cross border flow was minimal. For the scenario when the dam is initially full, the requirement was met with an improvement of 11% over the observed flows.
A TIME-DEPENDENT GREEN ELEMENT FORMULATION FOR SOLUTION OF POTENTIAL FLOW PROBLEMS IN 3 DIMENSIONAL DOMAINS
(University of the Witwatersrand, Johannesburg, 2010) Nyirenda, Edwin
In this work we develop a generalised methodology for the solution of the time dependent second order parabolic differential equation of potential flow in heterogeneous media using the Green element method. Parabolic differential equations are one class of differential equations, the others being elliptic partial differential equations and hyperbolic differential equations. Since elliptic differential equations generally arise from a diffusion process that has reached equilibrium, they can also be solved using the methodology developed, and represent a simplification because of the steady state situation. Potential flow problems are of great interest in many engineering applications such as flow in aquifers, heat transfer processes, electro-magnetic field problems, etc. Traditionally, the finite difference method and the finite element method have proved to be powerful techniques to solve such potential flow problems, but each has limitations and challenges which have led to continued research in numerical methods. The finite difference method is more applicable to domains with regular boundary, and the finite element method, though extremely versatile, exhibits unacceptable inaccuracies with coarse meshes, thus requiring fine meshes with the associated high computation costs. In view of some of the limitations with these earlier methods, several numerical schemes are now being developed as viable alternatives to these conventional methods. Among such methods are the boundary element method, the finite volume method, and the analytic element method. The boundary element method has been particularly promising because of its domain-reduction feature and the second order accuracy that can generally be achieved. The domain-reduction feature of the boundary element method, though achieved for restricted class of problems, lends it to efficient grid generation algorithm, while its second-order accuracy ensures reliability and consistency of the numerical solutions.-iv _________________________________________________________________ The boundary element method in its original formulation is unable to deal with heterogeneities in the domain. For physical problems, especially in groundwater flow, heterogeneities and anisotropy are a natural and frequent occurrence, and this has fuelled research into boundary element techniques that are capable of accommodating these features. The Green element method is one technique which is based on the boundary element theory and which has been proven to be very effective in handling heterogeneities and anisotropy in 1D and 2D domains. However, development of techniques to implement the Green element method in 3D domains has remained largely unexplored. This work represents an effort in this direction. We have investigated the adoption of the general tetrahedral and hexahedra elements for use with the Green element method, and found that the large number of degrees of freedom generated precludes retention of the internal normal direction as in 1D and 2D formulations. Furthermore, some of the complicated surface and domain integrations with these elements can only be addressed with quadrature methods. The compatibility issues that arise between element faces, which present considerable challenges to multi-domain boundary element techniques, are innovatively addressed in the computer code that has been developed in this work. The Green element method is implemented for steady and time-dependent problems using regular hexahedra elements, and the results show that the performance is slightly better than the results obtained using FEMWATER. FEMWATER is an established finite element method software. No attempt is made to compare the computation efficiencies of the 3D GEM code and FEMWATER because the two codes were not developed on a common platform.
QPSK DS-CDMA System over Rayleigh Channel with a Randomly-Varying Frequency Narrow-Band Interference: Frequency Tracking Analysis.
(Scientific Research., 2010-03) Mvuma, Aloys N.
This paper analyzes frequency tracking characteristics of a complex-coefficient adaptive infinite-impulse response (IIR) notch filter used for suppression of narrow-band interference (NBI) with a randomly varying frequency in a quadriphase shift keying (QPSK) modulated direct-sequence code-division multiple-access (DS-CDMA) communication system. The QPSK DS-CDMA signals are transmitted over a frequency non-selective Rayleigh fading channel. The analysis is based on a first-order real-coefficient difference equation with respect to steady-state instantaneous frequency tracking error from which a closed-form expression that relates frequency tracking mean square error (MSE) with the number of DS-CDMA active users and NBI power is obtained. Closed-form expressions for the optimum notch bandwidth coefficient and step size constant that minimize the frequency tracking MSE are also derived. Computer simulations are included to substantiatethe accuracy of the analyses.
BER of OFDM System With Multiple NBI Rejection Cascade Complex Coefficient Adaptive IIR Notch Filter
(Scientific Research, 2012-08-16) Mvuma, Aloys N.
In this paper, rejection of multiple narrowband interferers in a binary phase shift keying modulated orthogonal fre- quency division multiplexing (BPSK-OFDM) system is investigated. The BPSK-OFDM system in consideration oper- ates in an additive white Gaussian noise (AWGN) channel. A cascade complex coefficient adaptive infinite impulse response (IIR) notch filter with gradient-based algorithm is used to reject the interferers. Bit error ratio (BER) perform- ance of the system is studied and a general closed-form expression is derived assuming negligible steady-state leakage NBI and by estimating the decision variable as Gaussian distributed based on Central Limit Theorem (CLT). Depend- ence of the BER performance on the notch bandwidth coefficient is demonstrated by the analysis. Extensive simulation results are included to substantiate accuracy of the analysis.
Mapping the Distribution of Digitate and Tabulate Acropora Corals in Selected Reefs of Zanzibar
(Mbeya University of Science and Technology, 2013) Mwakalapa, Eliezer. Brown
Mapping the boundaries and distribution of reef corals, especially at growth form level, is an important coastal zone management step. Digitate and tabulate Acropora are growth forms of stone corals associated with abundance of reef fishes and are important in building reef framework. In this study boundaries of coral reefs and the distribution of digitate and tabulate Acropora around Bawe and Mnemba Islets, Zanzibar Island were mapped and results compared with environmental parameters. Data were collected by manta tow technique, line intercept transect, belt intersect transect, GPS unit and an underwater camera. Geo-referenced data was processed using ArcMap 9.3 software. The border line was set where live coral cover was above 5%. At the boundaries reef corals are intermixed with seagrasses, sand, rock and algal mats. The estimated area of coral reef was 1.9 km2 at Bawe Island and 20 km2 at Mnemba Island. Tabulate Acropora were aggregated on Bawe and Mnemba coral reefs, while digitate Acropora were aggregated on the reef flats, randomly distributed on Bawe and dispersed on Mnemba reef slopes. Small sized colonies of 11 to 40 cm and 21 to 60 cm diameters dominated the distributions of digitate and tabulate Acropora respectively. Higher contribution of digitate Acropora (2.07 cm) were observed in terms of coral cover as compared to tabulate Acropora (0.03 cm). The study also revealed that the distribution of tabulate and digitate Acropora is influenced by depth, turbidity and habitat type. This study provides useful information on the location and distribution of digitate and tabulate Acropora and provides recommendations for management and future studies on ecosystem changes and vulnerability.
Estimation of Extreme Flows in Nkana River to Verify the Adequacy of Naming’ongo Bridge Waterway.
(Scientific Research, 2013-02-05) Katambara, Zacharia; Msambichaka, Joseph J.; Mkisi, Joseph
The response by the government of Tanzania to food security and poverty alleviation in the Naming’ongo area in Mbozi District has been to develop Naming’ongo irrigation scheme as well as construct a bridge across River Nkana to connect the farms and other parts of the district to facilitate a reliable transportation of the produce to the market. The Australian Water Balance Model was calibrated by using 10 years data from a nearby sub-catchment of Mbarali. The Naming’ongo Sub-catchment was delineated form a 30 m digital elevation model. The observed rainfall was obtained from Mbozi Meteorological station. The study approximated the peak flows in River Nkana for a return period of 50 years to be slight above 560 m3 /s. This was considered to be adequate for the proposed structure. The study recommends that when undertaking human activities such as deforestation and cultivation an account for soil and environmental conservation should be considered. While it is necessary to establish a monitoring system within the catchment, the designs of future hydraulic structures should incorporate stream flow measuring facilities.
Adopting the System of Rice Intensification (SRI) In Tanzania: A Review
(SciRes., 2013-06-02) Katambara,Zacharia; Kahimba, Frederick C.; Mahoo, Henry F.; Mbungu, Winfred B.; Mhenga, Fikiri; Reuben,Paul; Maugo, Muyenjwa; Nyarubamba, Anthony
The demand of water for irrigation purposes in Tanzania outstrips the amount of water available for irrigation and other demands. On the other hand, the demand for more food to feed the growing population is increasing, calling for the need to have technologies and farming practices that ensure more food production while minimizing water uses. Rice is among cereal crops grown in Tanzania, and it can assist in meeting the food demand for the nation. Majority of rice producers in Tanzania and Sub-Saharan Africa (SSA) are subsistence farmers and they practice continuous flooding, a technique that requires much water. In addition to using large amounts of water, the conventional practices of growing paddy using local varieties transplanting process are implemented when seedlings are more than 21 days old, and 3 - 4 seedlings are transplanted in one hole. This practice results in low yields, and low water productivity and water use efficiency. The system of rice intensification (SRI) on the other hand, is a promising new practice of growing paddy rice that has proven to be very effective in saving water and increasing rice yields in many parts of the world. SRI practice is spreading fast and it has been adopted in many countries. The SRI practice has been introduced in Tanzania during the last 3 years as such it is not widely practiced. This paper reviews SRI practice at global, regional and country (Tanzania) level, and evaluates the challenges, opportunities and implications for its adoption in Tanzania. Knowledge gaps at each level have been identified and discussed as well as suggestions for researchable areas.
Positioning Mbeya University of Science and Technology in Tanzania in the Systems of Innovation Perspective.
(Scienetific Research, 2013-10-06) Katambara, Zacharia
The chronological development of universities ranges from the state at which universities are considered to be knowledge accumulators followed by knowledge factories and finally the knowledge hubs. The various national systems of innovations are aligned with the knowledge hubs and it involves a substantial amount of research activities. The newly established Mbeya University of Science and Technology is recognized as a knowledge hub in some particular niches. However, there are a limited number of research activities conducted at the university and this study is an attempt to identify the reasons that limit research activities. Well-structured research questionnaires were designed and distributed to academic staff members and thereafter the respondents were analyzed by using SPSS software package. The lack of knowledge, skills and funds as well as equipment was earmarked as the reason that hindered the research activities. Therefore, resources are required to improve the capabilities of the staff members and the study recommends on the need for deliberate efforts to improve the knowledge of the staff members with respect to research activities.
Positioning Mbeya University of Science and Technology in Tanzania in the Systems of Innovation Perspective
(Mbeya University of Science and Technology Journal of Research and Development (MJRD), 2013-11-13) Katambara, Z
The chronological development of universities ranges from the state at which universities are considered to be knowledge accumulators followed by knowledge factories and finally the knowledge hubs. The various national systems of innovations are aligned with the knowledge hubs and it involves a substantial amount of research activities. The newly established Mbeya University of Science and Technology is recognized as a knowledge hub in some particular niches. However, there are a limited number of research ac activities conducted at the university and this study is an attempt to identify the reasons that limit research activities. Well-structured research questionnaires were designed and distributed to academic staff members and thereafter the respondents were analyzed by using SPSS software package. The lack of knowledge, skills and funds as well as equipment was earmarked as the reason that hindered the research activities. Therefore, resources are required to improve the capabilities of the staff members and the study recommends on the need for deliberate efforts to improve the knowledge of the staff members with respect to research activities.
Evaluation of Local Ceramic Materials for High Voltage Insulation Application
(Nelson Mandela African Institution of Science and Technology, 2014) Moyo, Moses George
This study investigated the Tanzanian local ceramic material for their potential as raw materials for production of high voltage insulators based on the mix proportion of raw materials and firing temperatures. The raw materials used were: Pugu kaolin, quartz supplied by the Kilimanjaro Industrial Development Trust (KIDT), and Kilimanjaro feldspar. The study characterised both individual raw materials and the blends produced from these raw materials. A total of six batches were prepared by varying the proportion of raw materials. Cylindrical samples of 10 and 60 mm diameter were produced by slip casting method and fired at the maximum temperature of 1100, 1200 and 1300 ºC. Fired samples were tested for insulation resistance, bending strength, and bulk properties. The X-ray diffraction (XRD) analysis showed that on heating Pugu kaolin produces mullite phase which is very important for mechanical and dielectric properties. Furthermore, the highest trend in insulation resistance and bending strength is revealed to samples fired at 1200 ºC with lower values for those fired at 1100 and 1300 ºC. The optimum mix proportion and firing temperature, which compromise both insulation resistance and bending strength is with 33 wt% Pugu kaolin, 11 wt% Kilimanjaro quartz, and 56 wt% Kilimanjaro feldspar at the firing temperature of 1200 ºC. With this mix proportion and firing temperature at maximum insulation resistance of 205800 MΩ at the injection of 1000 V is achieved. The bending strength and water absorption for this mix proportion and firing temperature is 65.358 MPa and 0.01 %, respectively. These results correspond to the standard specifications for ceramic insulators.
Ubiquitous Mobile Sensing for Water Quality Monitoring and Reporting within Lake Victoria Basin
(Scientific Research, 2014-12) Faustine, Anthony; Mvuma, Aloys N.
As the human population growth and industry pressure in most developing countries continue to increase, effective water quality monitoring and evaluation has become critical for water re sources management programs. This paper presents the ubiquitous mobile sensing system for water quality data collection and monitoring applications in developing countries. The system was designed based on the analysis of the existing solution. Open source hardware and software was used to develop the prototype of the system. Field testing of the system conducted in Nkokonjero, Uganda and Mwanza, Tanzania verified the functionalities of the system and its practical applica tion in actual environment. Results show that proposed solution is able to collect and present data in a mobile environment.
Influence of Number of Access Points for Fingerprinting Indoor Positioning Accuracy
(International Journal of Research in Advanced Engineering and Technology, 2016-05) Mrindoko, Nicholaus R.
The indoor positioning services based on fingerprinting mostly depend on the available access points in vicinity area. This paper explores the impact of number access points (APs) in indoor positioning accuracy based fingerprinting. The analysis is based on deterministic approach. The measurable analysis of test results demonstrates that, the positioning accuracy is highly affected by the number of access points. If the number of APs increased with well distribution positioning error is minimal. Hence, considering the adequate number of APs is guaranteeing an accuracy of an indoor positioning. The analysis could empower indoor positioning designer to enhance positioning performance and to model location fingerprinting based indoor positioning systems
An Investigation for Energy Sustainability in Cement Industries in Tanzania: The Case of Mbeya Cement
(Technische Universität Berlin Institut für Energietechnik, 2017) John, John Pius
Cement production processes are facing crucial sustainability issues such as inefficient en‐ ergy and raw material use, product supply, production cost and environmental pollution. High energy and material use dominated by inefficient characteristics of cement production processes, in turn, lead into depletion of non‐renewable resources, increased production costs as well as environmental degradation due to emissions. The main objective of the study was to investigate performance of cement industry in Tanza‐ nia relative to sustainable energy utilization. Most of past researches have evaluated the per‐ formance of cement production processes using first law of thermodynamics alone (mass and energy balances) with the objective of improving energy efficiency. Although this ap‐ proach sheds light on the question of improvement of energy use in the processes, it has some limitations. The limitations are imposed by the internal irreversibility due to combustion and other physico‐chemical nature of reactions dominating the whole processes. The current emerging approach, which overcomes limitations imposed to the first law approach is ex‐ ergy‐based method, relatively new in evaluation of performance of cement production pro‐ cesses. However, owing to complexity of cement production processes, applying an exergy‐ based method manually is very difficult and complex. The current study proposes combined approach of exergy based method and modeling as well as simulation. The model was successfully developed, validated using real plant data and was used to predict the performance of the cement dry rotary kiln system of Mbeya Cement production processes. Data obtained from modeling and simulation were further used to evaluate the performance of processes, individual components, sub‐systems and overall kiln system at large using exergy based method. The approach not only simplifies the analyses but also gives detailed insight of real processes, source and type of real imperfections, its magnitudes and how imperfections can be minimized. Major findings indicated that the rotary kiln sub‐systems and the overall kiln system have poor exergetic performance, suggesting that potential for improvement exists. The overall exergy efficiency of the kiln system is around 33 %. Also results indicated that the rotary kilns have the lowest exergetic efficiency of about 14 % followed by the clinker cooler with exergetic efficiency of about 41.11 %. The highest source of irreversibility encompassed chemical reactions, especially calcination and clinker burning processes with exergy destruc‐ tion of 2,813.75 kJ⋅kgcl−1 and 1,148.17 kJ⋅kgcl−1. Results from parametric analysis suggested that if measures for improvements of processes, components and sub‐systems are taken, a significant amount of fuel and specific energy could be saved. Furthermore, it was confirmed that if the avoidable exergy destruction is minimized, processes, system components and sub‐systems performance could be improved from exergetic point of view.
Optimizing the Conjunctive Use of Surface Water and Groundwater in Water Stressed River Basins: Case of Olifants River Basin, South Africa
(Tshwane University Of Technology, 2017) Kifanyi, Gislar Edgar
One of the new techniques currently used to address water shortage problems in the developed countries is the optimum conjunctive water use. Optimum conjunctive water use demands that the surface and subsurface reservoirs are fully characterized if deterministic methods are to give reliable results. However, in real world phenomena, full characterization of surface – groundwater reservoirs is neither practically nor economically feasible. This research, therefore, aimed at developing a combined simulation-optimization quantitative conjunctive water use management model which can sustainably manage water resources taking into account input parameter uncertainty. Response matrix technique was used to combine simulation model with optimization model (procedure). The novelty of this research work is that determination of optimum conjunctive water use was determined under scanty data and uncertain condition. Surface water and groundwater conceptual models were developed, and integrated to form a conjunctive water use conceptual model which was converted into numerical simulation model for both deterministic and stochastic simulations. MODFLOW 2000 and RIVER Package (RIV) (together referred to as conjunctive water use simulation model) supported in Visual MODFLOW 2014.2 Classical Interface was used to determine aquifer system responses (drawdowns). These drawdowns were assembled as response matrices and then incorporated into an optimization management model as drawdowns constraints coefficients. The simulation optimization problems were solved and analysed through “Active-Set” (Sequential Quadratic Programming (SQP) optimizer (algorithm)) implemented under the MATLAB 2014a environment. The Retrospective Optimization Approximation (ROA) method was used for solving the stochastic optimization problem and to v investigate the impact of uncertainty on optimal management strategies. ROA procedure solves and evaluates a sequence of optimization sub-problems in an increasing number of realizations. Results indicated that the study area aquifer has potential groundwater resource which is undeveloped. Deterministic approach underestimates the water withdrawal rates. The optimal withdrawal rates designed based on ROA approach were relatively higher than those designed based on deterministic approach. Moreover, the overall percentages of contribution of surface water and groundwater sources to the total water demand obtained through ROA approach was about 58% and 42%, respectively while the overall percentages contribution obtained through deterministic approach was about 85% and 15%, respectively. This is about ±27 % variation (i.e., Differences between the approaches realized) of percentages of contribution of the two water sources to the total water demand. Furthermore, findings indicated that ROA conjunctive water use management technique has potential to ensure sustainability of limited water resources of river basins. Through ROA approach the expected total optimal objective function value converged to its maximum value within a relatively few iterations (6 to 8 iterations) in about 2.30 Hrs computational time. In conclusion, results demonstrated that the ROA approach is a promising technique for use in managing conjunctive water use under uncertainty conditions. It is recommended that guidelines for determination of the sequence of sample sizes for use in ROA method framework should be established. The use of parallel computer processors to enhance computational time efficiency for large optimization problems should be explored. Quantitative methods for determination of weights for estimating values of objective functions should be investigated. The application of the ROA approach to multi-objectives optimization problems should be explored.
Synthetic Determination of Specific Density, Specific Surface Area and Particle Size Distribution of Cementitious Powder Materials
(International Journal of Sciences: Basic and Applied Research (IJSBAR), 2018) Dr. Chengulaa, Duwa Hamisi; Prof. Msambichaka, Joseph J; Prof. Middendorf, Bernhard
The use of cementitious materials for construction of buildings and structures started during ancient civilization. Science of modifying physical and chemical properties of cementitious materials is a continual process which is because of a need to increase reactivity and improve strength and durability properties of binders. Due to increasing demand of modern infrastructures and continual depleting of binder sources the scientist, engineers and researchers work hard on improving binding properties of cementitious materials for construction of low cost and durable structures. Among of the factors which affect binding properties of cementitious properties are densities, surface areas and particle size distribution. Several methods and procedures have been developed to determine these physical properties on which other require huge capital investment and others takes long time to complete a test which hinders further investigation and improvement of alternative binders. This study investigated that there exists an ‘S’ curve similar to particle size distribution curve when time air flow against weights of sample measured using Blaine apparatus is drawn.
Effect of Ipomoea Hildebrandtii and I. Kituiensis on Loss of Native Herbages of Maasai Steppe Rangelands in Simanjiro District
(The University Of Dodoma, 2018) Ndaki, Manyanza
Sustainability of many rangelands including Simanjiro Maasai steppe rangelands is limited in part by invasive plant species. A study was conducted among two selected village rangelands (Terrat and Sukuro) of the Simanjiro district aimed to (1) determine the effect of Ipomoea hildebrandtii and I. kituiensis on herbage species composition, richness, and basal cover; and (2) determine the effect of Ipomoea hildebrandtii and I. kituiensis on herbage biomass productivity. Other objectives were to (3) assess the distribution of Ipomoea hildebrandtii and I. kituiensis across grassland and woodland habitats, and (4) evaluate the available mitigation measures among the Maasai pastoralists on the effects of Ipomoea hildebrandtii and I. kituiensis on their rangelands. A total of 10 plots of 70 m2 each with 9 quadrats of 1 m2 each in the invaded and non-invaded grazing-lands coupled with point sampling technique. Purposeful sampling involved 10 key informants’ interviewees; 24 participants for focus group discussions. Simple random sampling involved 30 hamlets representatives for questionnaire surveys. Data on herbage species composition, richness, basal cover, biomass productivity; distribution of invasive Ipomoea spp; and mitigation measures for effects of invasive Ipomoea spp. were analysed using STATA, Microsoft Excel and SPSS, respectively. Non-invaded grazing-lands had a higher basal cover (54.71%±1.95% for grasses, 45.29%±1.95% for forb) than invaded grazing-lands (29.38%±1.34% for grasses, 24.70%±1.20% for forb), (P0.05). Non-invaded grazing-lands had higher biomass productivity (0.289±0.03 t DM/ha) than invaded grazing-lands (0.202±0.02 t DM/ha), (P
Uncertainty Reduction in Climate and Hydrological Models Predictions at Catchment Scale In the Upper Great Ruaha River Sub-Basin, Tanzania
(Sokoine University of Agriculture, 2019) Mutayoba, Edmund Ishengoma
Water resources have become scarce in most tropical areas of Tanzania due to climate change. Any changes to the hydrological cycle may have significant effects on the water resources in the river basins of Tanzania. The impact of climate change on water resources in Tanzania have been studied using General Circulation Models (GCM) which run at low spatial resolutions of 100-300 km. The resolution is too coarse to provide useful information about climate change impact in small catchments as many physical processes which control local climate e.g.; vegetation, hydrology, topography is not fully parameterized and hence results on uncertainty in model prediction. The main aim of this research was to quantify the uncertainty in model predictions for the Mbarali River Sub-catchment of the Upper Great Ruaha River Sub-basin in the Rufiji River Basin, Tanzania. Three research objectives were analyzed; the first objective was to evaluate the performance of the Coordinated Regional Downscaling Experiment Regional Climate Model (CORDEX, Regional Climate Models) in simulating rainfall characteristics of the Mbarali River Sub catchment. The area weighted average method was used to calculate the average rainfall from the CORDEX RCMs and from ERA-Interim reanalysis over the entire Mbarali River sub-catchment. Comparison between rainfall data from CORDEX RCMs and ERA-Interim reanalysis was done to test the ability of the CORDEX RCMs to reproduce the annual cycles, interannual variability, annual total and trends of rainfall as presented by the ERA-Interim reanalysis. The second objective assessed the impact of climate change on hydrological characteristics using the Soil and Water Assessment Tool (SWAT) model. The ability of the SWAT model to simulate catchment processes was assessed through a calibration and iii validation process, which was a key factor in reducing uncertainty and increasing user confidence in its predictive abilities. The SWAT model was driven by high resolution climate simulations for historical climate condition (1971-2000) as well as future climate projections (2011-2040, 2041-2070 and 2071-2100) for two Representative concentration Pathways (RCPs): RCP 4.5 and RCP 8.5. Furthermore, Ensemble of RCMs was applied into SWAT to simulate water resources availability and the results were compared with individual models (HIRHAM5, CCLM4, RACMO22T, RCA4). The Rainfall and Temperature data were obtained from the selected four CORDEX RCMs driven by three different General Circulation Models (GCMs). Inverse Distance Weight Average (IDWA) was used to interpolate model gridded climate simulation to the location of weather station. The third objective assessed the impacts of land use and land cover change on the hydrology using integration of remote sensing data, QGIS and SWAT model. The land use and land cover (LULC) maps for three window period snapshots, 1990, 2006 and 2017 were created from Landsat TM and OLI_TIRS. Supervised classification was used to generate LULC maps using the Maximum Likelihood Algorithm and Kappa statistics for assessment of accuracy. The findings of the first objective are that CORDEX RCMs were able to capture well the seasonal and annual cycles of rainfall. However, they underestimated the amount of rainfall in March, April and May (MAM) and overestimated in October, November and December (OND) respectively. CORDEX RCMs reproduce interannual variation of rainfall. The source of uncertainties was revealed when the same RCMs driven by different GCMs and when different RCMs driven by the same GCM in simulating rainfall. It was found that the error and biases from RCMs and driving GCMs contribute roughly equally. Overall, the evaluation found reasonable (although variable) model capability in representing the mean climate, interannual variability and rainfall trends. iv The results suggest that CORDEX RCM is suitable in simulating rainfall, maximum temperature and minimum temperature. The findings of the second objective showed that SWAT model simulated stream flow and water balance components differently when two different RCMs were forced by the same GCMs as well as when the same RCMs were forced by different GCMs. The differences are related to the formulation of the RCMs themselves. For example, RACMO22T and HIRHAM5 driven with the same GCM (ICHEC-EARTH) simulate different amount of stream flows, surface runoff, water yield and groundwater yield in historical (1971–2000) as well as in present century (2011-2040), mid-century (2041- 2070) and end century (2071-2100). Ensemble RCMs projected decrease in stream flows by 13.67% under RCP 8.5. However annual rainfall was shown to increase in averages by 1.62% under RCP 4.5 and by 1.96% for RCP 8.5 relative to the 1177.1mm of the baseline period (1971-2000). The results also showed that, temperature will slightly increase relative to the baseline during present century (2011-2040) for RCP 4.5 and RCP 8.5. The ensemble average project that the minimum temperature will increase by 14% (1.90C) under RCP 8.5 and maximum temperature by 7.68% (1.8oC) under RCP 4.5 The findings of the third objective showed that there were significant changes in land use and cover for the three-time periods (1990, 2006 and 2017). The cultivated land and built up area increased from 25.69% in 1990 to 31.53% in 2006 and 43.57% in 2017 compared to other land classes. Increase of cultivated land and built up area led to decrease in forest cover. Forests occupied 7.54% in 1990, but decreased to 5.51% in 2006 and 5.23% in 2017. This decrease in forest cover has resulted in increased surface runoff for the same v periods (2006-2017). The increase in surface runoff in the study area could be attributed to deforestation and poor land husbandry, where during land preparation much of the vegetation is cleared, hence decreasing canopy interception and allowing water to drain off. Also, poor farming practices including cultivation on hillslopes without soil conservation, reducing soil compaction, hence allowing more water to drain as surface runoff. The calibrated SWAT model using the three different land use and land cover change of 1990, 2006 and 2017 indicate that during the wet season, the mean monthly flow increased by 1.48% relative to the 28.09 m3 /s of the baseline 1990 while during the dry season, the mean monthly flow decreased by 16.7% relative to the 0.20 m3 /s baseline flow. Assessment of the impacts of land use and land cover changes on catchment water balance component revealed that surface runoff increased by 3.9% in 2006 and 9.01% in 2017 while groundwater contribution to stream flow decreased by 6.3% and 12.86% in 2006 and 2017, respectively. The decrease in stream flow could also be attributed to abstraction of water for irrigation activities upstream of the Igawa gauge station. The findings of the study may help basin water officers, planners in water sector and agriculture sector in addressing uncertainty in policy and decision-making specifically when preparing strategies and adaptations plans for river catchment. The science used in this study can be applicable to another river basin in Tanzanian in a climate change impact study.

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