UWCScholar :: Browsing by Author "Mazvimavi, Dominic"

Browsing by Author "Mazvimavi, Dominic"

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A comparative analysis of long-term variations of temperature and rainfall in rural and urban areas, and their effects on the estimation of design storms in Kenya
(University of the Western Cape, 2016) Gachahi, Lydiah Wangechi; Mazvimavi, Dominic
My Thesis aimed at expanding the current knowledge on how variations of temperature characteristics including the possible existence of urban heat islands (UHI) over urban areas of Kenya could be influencing rainfall characteristics, and to examine if the stationary extreme value distributionis still suitable for modeling urban storm designs in view of the global climate change. My hypothesis was that the floodingoccurring frequently in major urban areas of Kenya are due to increased rainfall caused by global climate change, and the urban heat island (UHI) effect. To put this perception into perspective, temperature and rainfall characteristics and their inter-relationships, of four of the major urban areas in Kenya namely, Nairobi, Mombasa, Kisumu, and Nakuru, were investigated. I obtained data from meteorological stations in and around each urban area, which had at least thirty (30) years of continuous monthly (or daily) temperatures and rainfall values, from the Kenya Meteorological Department. I checked the datasets for quality and missing values and adjusted where necessary before commencing with analysis. I sourced other supporting global dataset from various websites' data banks.I used various methods of data analysis which included; i) exploratory data analysis techniques such as the continuous wavelet transform (CWT), geographical information system (GIS) maps, and visual time series plots. In particular and unique in my Thesis was the use of the CWT method as a diagnostic tool to examine non-stationaritiesand variability of temperature and rainfall time series.
An analysis of sustainability of communally-managed rural water supply systems in Zimbabwe
(University of the Western Cape, 2016) Kativhu, Tendai; Mazvimavi, Dominic
Sustainability of rural water supply systems is a major development challenge in most developing countries including Zimbabwe. This thesis aimed to analyse the sustainability of communally managed rural water supply systems in Zimbabwe. Specifically, it determined the factors influencing sustainability of water supply systems; investigated how the implementation of Community Based Management (CBM) is contributing to the sustainability of water supply systems; explored how multiple uses of water influence sustainability of water supply systems under CBM and determined how the principal factors influencing sustainability and the CBM implementation practices, can be incorporated at the different stages of the development of a water supply system. The study was done in Nyanga, Chivi and Gwanda districts. A total of 399 communally- managed water points were studied and 300 households participated in the study. Questionnaires were used to collect data from households and Water Point Committees (WPCs). Data was also collected using Key Informant Interviews (KIIs) with a total of 33 key informants being drawn from the national, district and community levels.
An assessment of long-term and large-scale wetlands change dynamics in the Limpopo transboundary river basin using cloud-based earth observation data
(Springer Science and Business Media B.V., 2024) Gxokwe, Siyamthanda; Dube, Timothy; Mazvimavi, Dominic
Significant progress has been made in monitoring and assessing the effects of land use and land cover (LULC) changes on wetland extent. However, our understanding of wetland within the transboundary basins has been limited by the scarcity of available data on their dynamic changes over time. This study aimed to address this gap by analyzing the long-term and large-scale spatio-temporal extent of wetland in the Limpopo transboundary river basin (LTRB) over a 20-year period (2000–2020). To achieve this, we utilized the Google Earth Engine (GEE) cloud-computing platform and various remotely sensed data. The study had two primary objectives; (1) to examine LULC changes over time using machine learning algorithms applied to multisource remotely sensed data in GEE, and (2) to assess the relationship between LULC changes and the extent of wetlands in the basin. A total of nine land cover classes were identified, including shrublands, croplands, bare-surface, wetlands, sparse vegetation, tree cover, built-up areas, and grasslands. Shrublands covered 76–82% of the LTRB. On the other hand, wetlands and sparse vegetation were the least dominant, with proportions ranging from 0.3 to 2%. The overall accuracy of the classification results was within acceptable ranges, ranging from 77 to 78%. The study further revealed a continuing decline in wetlands extent and sparse vegetation, with average rates of 19% and 44%, respectively. Conversely, shrublands, croplands, and tree cover showed an increase, with average rates of 0.4% and 12.4% respectively. A significant finding was the replacement of a substantial portion (40%) of wetland areas with built-up areas, indicating that urban expansion is a major driver of wetland shrinkage in the study area. These results provide valuable insights into the declining extent of wetlands in the LTRB. Such findings are crucial for environmental management efforts, as they provide information on which wetlands should be prioritized when implementing strategies to prevent the negative impacts of LULC changes on wetlands in the area. Therefore, contributing towards achieving sustainable development goals relating to freshwater ecosystems protection and management.
Assessing land use-land cover changes and their effects on the hydrological responses within the Nyangores River Catchment, Kenya
(University of Western Cape, 2021) Ndungo, Margaret Njoki; Mazvimavi, Dominic
This thesis aimed at contributing knowledge on how the widespread changes in land use/cover resulting from increasing human population and their associated activities, are influencing hydrological responses in a sub-humid catchment. The study therefore hypothesised that reduced forest cover over time in favour of agricultural activities is altering hydrological processes of the catchment which is affecting the flow characteristics in a sub-humid catchment. The sub-humid catchment selected to investigate these issues is the Nyangores River Catchment in Kenya.
Assessing the effect of the Kars Wetland on flow attenuation in the Cape Agulhas, South Africa
(University of the Western Cape, 2019) Hans, Damian Trevor; Mazvimavi, Dominic
The Kars has a well-defined channel along the 62 km stretch from its sources in the Bredasdorp Mountains. After entering the Agulhas plain which has a very low gradient, this river changes into a triangular shaped wetland. This wetland is 7 km in length with no defined channel running through it. The wetland then discharges into another 7 km long channel that joins the Heuningnes River with its mouth at the Indian Ocean. The presence of the wetland causes frequent flooding which affects cultivated lands and a major highway linking towns on the coastal Cape Agulhas area with the rest of the country. Before this study, there was no monitoring of flows along the Kars River including water levels within the wetland. Consequently, the conditions leading to flooding of the wetlands were unknown. This study is aimed at understanding how the combination of local rainfall, Kars River inflow into the wetland, soil characteristics, and the morphology of the wetland influence flooding/inundation. The study monitored river inflows into and outflows from the wetland. A soil survey was conducted within the wetland using the augering method and an infiltrometer to determine soil type and infiltration rates. This was done to assess the hydrological characteristics of the wetland. Using the collected climate data and river flow data, a conceptual model was developed for predicting downstream outflows and possible flood events on a daily timescale. The results indicated that the Kars wetland comprises soil with high silt and clay content, and low infiltration capacity. The wetland causes flood attenuation and diffuse surface flows. Low infiltration rates result in ponding of local rainfall which can contribute to flooding.
Assessing the effects of non-stationarity on reservoir yield estimations: A case study of the Southern Okavango integrated water development system in Botswana
(John Wiley and Sons Ltd, 2024) Mazvimavi, Dominic; Kapangaziwiri, Evison; Gumbo, Anesu Dion
Streamflow data used for water resources planning should ideally be stationary, and any non-stationary behaviour is taken into account. However, with limited time series data, the influence of non-stationarity is often hidden and can result in unreliable estimates. This paper examines the impact of non-stationarity on the Southern Okavango Integrated Water Development (SOIWD) project that was carried out with streamflow collected between 1969 and 1989 against an extended time series from 1990 to 2019. To achieve this, (a) the statistics of these inflows and (b) the reliability of satisfying water demands from the proposed reservoirs were tested based on the two periods (1969–1989 and 1990–2019). The results show that average monthly flows for July, August and September significantly change when peak outflows from the delta occur. Given the expected variability of the flow regime, an uncertainty approach utilising flow perturbation from ±5% to ±90% was also used to investigate the system's response to changes in the driving flow conditions. The increasing availability of flow data from 1990 to 2019 has shown that the SOIWD system would not have satisfied the water demand as it would not be operationally viable. This confirms the importance of accounting for non-stationarity in reservoir yield estimation and reemphasises its importance in hydrological studies
Assessing the variation of river channel reach inflows on transmission losses
(World Water Policy, 2022) Mazvimavi, Dominic; Mujere, Never; Masocha, Mhosisi; Makurira, Hodson
Arid and semi-arid regions are characterized by limited water availability throughout the year and highly variable streamflows. River channel transmission losses add another uncertainty to the complex flow regimes. However, the contribution of different factors influencing to transmission losses is poorly understood. In this work we determined whether variations in river channel transmission losses along five reaches of varying lengths could be related to reach inflows in Runde River catchment in Zimbabwe. We directly estimated transmission losses as the difference between reach inflow and outflow discharges. Using simple bivariate regression equations, channel transmission losses were modelled as response variables while reach inflows were the predictor variables. Our results indicate statistically significant positive relationships (p = .000, R2 > 0.05) between inflows and transmission losses for all minor, moderate, and major flow events. This simple approach can be applied in similar settings to understand the variations in transmission losses
Assessment of the contributions of water allocation reforms to achieving equitable access to water by smallholder emerging farmers in the Breede-Gouritz catchment management agency
(University of the Western Cape, 2018) Mnyaka, Sinazo; Mazvimavi, Dominic
The National Water Act of (1998) of South Africa has a goal of achieving equitable access to water resources, as well as achieving environmental sustainability and efficient use of water. Consequently, water resources management is being reformed to ensure the achievement of these principles. Allocation of water through granting of licenses for abstraction and storage of water has been implemented to ensure that historically disadvantaged individuals (HDIs) have access to water and to promote sustainable, efficient and beneficial use of water resources for the whole country. The Water Allocation Reform Policy is a tool that is used to implement the goal of the National Water Act and it is guided by the set objectives, which are to allocate 30% of all water to previously disadvantaged individuals by 2014, 45% by 2019 and 60% by 2025. Despite these efforts, there is evidence that smallholder emerging farmers who are part of the disadvantaged groups do not have access to water for productive use. Many studies conducted so far have shown that equitable, sustainable and efficient water allocation has not been achieved in South Africa. It is not very clear why this trend is continuing despite all efforts to the contrary. The aim of the study was to assess the contribution of the reforms of water allocation systems towards increasing access to water by historically disadvantaged groups in Barrydale area in the Western Cape Province, South Africa. Interviews were conducted to determine how the reforms have influenced access to water for productive use by smallholder emerging farmers. Document review was undertaken to determine the progress in the implementation of the water allocation reform by the Breede-Overberg Catchment Management Agency (BGCMA). The results indicated that small-scale farmers do not have access to water for agricultural activities in Barrydale due to lack of components, which include financial funding, access to farming infrastructure and skills. The BGCMA has not completed the implementation of the Water Allocation Reform and as a result, mechanisms initiated by the BGCMA have not resulted in improved access to water by HDIs. The outcome of the study indicated a lack of implementation of the water allocation reforms by the BGCMA, hence there is still no increase to water access for agricultural use by HDIs.
An assessment of the influence of water allocation on sustainable water resources management: A case study of the Nyando river basin, Kenya
(University of the Western Cape, 2018) Sungu, Ronald O.; Mazvimavi, Dominic
Water problems prevalent in the Nyando River Basin are due to an ineffective water allocation system and lack of adequate conditions for implementation of sustainable integrated water resources management (IWRM) strategies. The basin is bedevilled by poor water resources management, inequitable allocation of water among consumers, physical infrastructural deficiencies, inefficient water utilisation, illegal water abstractions, natural resource mismanagement, conflicting and weak institutional roles and lack of stakeholder involvement in water resource management. The results of the study reveal sufficient per capita annual water availability with the potential to realise both Sustainable Development Goals (SDGs) and the Kenyan Vision 2030. However, analyses from flow duration curves (FDCs) and the water evaluation and planning (WEAP) model show that monthly water demands including environmental flow requirements (EFRs) are met only between 43% and 94% of the time. While the Water Act (2002) upholds the principles of IWRM on equitable and sustainable water resources allocation, in practice the current water allocation system falls short of implementing these strategies due to lack of a water allocation plan (WAP), inadequate water demand management (WDM), low infrastructural development and lack of community participation in WRM. For example, the total revenue generated in water supply schemes is only about 25 to 30% of their operational costs, which means that in the absence of subsidies the schemes cannot operate. The goal of this study was to examine the influence of the current water allocation system on water resources management in the Nyando River Basin by comparing the various sectoral water demands in the basin with the available water resources in order to improve understanding of how water allocation systems work in practice. The analyses further revealed that irrigation uses up to 72% of the available water, which is mainly drawn from the regular low flow contrary to the permit order. For example, the Ahero National Irrigation Scheme is permitted to draw 47 m3/day of water from regular flow and 13,500 m3/day from flood flow, but draws the whole amount from the regular flow; hence irrigation is the main cause of water deficits in the basin. Projections show that the irrigation sector will experience 300% increase in an unmet demand of 92.4 Mm3 by 2030 up from the current annual deficit of 2.9 Mm3. In light of the above challenges, both improvement of WDM and infrastructural provision have complementary roles in contributing to sustainable water availability, socioeconomic growth and poverty eradication in the basin and help achieve SDGs at the local scale. The results of the study will facilitate an understanding of the influence of water allocation systems on regional hydrology and form the basis of improving water allocation systems, and inform policy formulations to ensure sustained water availability and environmental sustainability in river basins. In that regard, this study contributes to the on-going global debate on Sustainable Development Goals by exploring ways of realising and improving IWRM strategies and the National targets.
An assessment of water use by riparian and non-riparian invasive alien plants and the effects on water resources at the catchment scale
(University of the Western Cape, 2023) Mkunyana, Yonela Princess; Mazvimavi, Dominic
The diversity and increasing extent of invasive alien plants (IAPs) are currently a global ecological and economic problem, especially in semi-arid regions. The introduction of IAPs worsens the strain in South Africa’s water resources by reducing the mean annual runoff by approximately 7%. Further work needs to be done to ensure that those IAPs that have the greatest impact receive priority. Effective management of IAPs promotes the conservation and sustainable use of the natural environment, the economies it supports, and the high quality of life in society. The monitoring of the distribution of IAPs is therefore an important consideration in catchment management. Remote sensing and cloud computing platform, Google Earth Engine (GEE) were used to map land use/landcover changes between the 1973 – 2021 period using Landsat imagery.
Characterization of flowpaths to improve the prediction of vegetation impacts on hydrological processes in semi-arid mountainous catchments of the Cape Fold Belt
(University of Western Cape, 2021) Jumbi, Faith Tatenda; Mazvimavi, Dominic
Mountainous areas are important water sources in many landscapes. An understanding of how mountainous catchments function is important particularly in semi-arid areas, where water shortages are prevalent. In addition to climate and physiographic factors, the hydrological responses of mountainous catchments can be influenced by land uses and land cover types. Although the general effects of land use and land cover types on hydrological processes are known, prediction of the specific effects in a given catchment is still problematic. This study characterized flowpaths, and hydrological responses to different land cover types in a semi-arid, mountainous Kromme River catchment (Eastern Cape province of South Africa), located in the Cape Fold Mountains of the Table Mountain Group (TMG) geological region.
Correction: sibanda et al. application of drone technologies in surface water resources monitoring and assessment: a systematic review of progress, challenges, and opportunities in the global south. drones 2021, 5, 84
(Drones, 2022) Dube, Timothy; Mazvimavi, Dominic; Sibanda, Mbulisi; Mutanga, Onisimo
In the original publication [1], “Fahad Alawadi. Detection of surface algal blooms using the newly developed algorithm surface algal bloom index (SABI)”, “Proc. SPIE 7825, Remote Sensing of the Ocean, Sea Ice, and Large Water Regions 2010, 782506 (18 October 2010); https://doi.org/10.1117/12.862096” [2] was not cited. The citation has now been inserted in “3.5. The Role of Drone Data Derived Vegetation Indices and Machine Algorithms in Remote Sensing Water Quality and Quantity” as reference [60] and should read: “Numerous vegetation indices were derived from drone remotely sensed data for characterizing surface water quality and quantity. The most widely used sections of the electromagnetic spectrum in detecting water quality parameters were the visible section (blue and green) and the NIR wavebands. In this regard, vegetation indices such as the red and near-infrared (NIR), Surface Algal Bloom Index (SABI) [60], two-band algorithm (2BDA) [26], NDVI, and Green NDV [33], as well as band combinations and differencing such as (R+NIR/G) were used mostly in characterizing chlorophyll content as well as TSS.
Dynamics and scales of transmission losses in dryland river systems: a meta-analysis
(AUSTRALASIAN JOURNAL OF WATER RESOURCES, 2021) Mazvimavi, Dominic
In this paper, 245 studies were reviewed to understand approaches used for estimating river channel transmission losses. Findings indicate that regression equations, differential equations, flow routing, experimental approaches and water balances are most widely used. Geographic Information Systems are becoming a convenient framework to display model results showing spatial variability of losses. In the United States, regression equations and experimental approaches involving controlled releases are widely used to assess transmission losses whereas in the dryland regions of Australia, water balance and flow routing approaches are popular. In Africa and Asia, regression equations and water balances are common approaches to estimate transmission losses. By using regression equations on data pooled from studies done in different dryland regions of the world, statistically significant (p<0.05) relationships were observed between transmission loss volume and, reach length, inflow, flow contributing area and runoff coefficient. Overall, the review underscores the importance of channel and catchment characteristics in shaping the dynamics of transmission losses. Two main limitations of the current approaches are that they are site-specific and require high amounts of data not always available in dryland regions due to sparse network of monitoring stations. The review also highlights existing knowledge gaps and future research needs.
Effects of land-cover - land-use on water quality within the kuils - Eerste River Catchment
(University of Western Cape, 2012) Chingombe, Wisemen; Thomas, Abraham; Mazvimavi, Dominic
The most significant human impacts on the hydrological system are due to land-use change. The conversion of land to agricultural, mining, industrial, or residential uses significantly alters the hydrological characteristics of the land surface and modifies pathways and rates of water flow. If this occurs over large or critical areas of a catchment, it can have significant short and long-term impacts, on the quality of water. While there are methods available to quantify the pollutants in surface water, methods of linking non-point source pollution to water quality at catchment scale are lacking. Therefore, the research presented in this thesis investigated modelling techniques to estimate the effect of land-cover type on water quality. The main goal of the study was to contribute towards improving the understanding of how different landcovers in an urbanizing catchment affect surface water quality. The aim of the research presented in this thesis was to explain how the quality of surface runoff varies on different land-cover types and to provide guidelines for minimizing water pollution that may be occurring in the Kuils-Eerste River catchment. The research objectives were; (1) to establish types and spatial distribution of land-cover types within the Kuils-Eerste River catchment, (2) to establish water quality characteristics of surface runoff from specific land-cover types at the experimental plot level, (3) to establish the contribution of each land-cover type to pollutant loads at the catchment scale. Land-cover characteristics and water quality were investigated using GIS and Remote Sensing tools. The application of these tools resulted in the development of a landcover map with 36 land classifications covering the whole catchment. Land-cover in the catchment is predominantly agricultural with vineyards and grassland covering the northern section of the catchment. Vineyards occupy over 35% of the total area followed by fynbos (indigenous vegetation) (12.5 %), open hard rock area (5.8 %), riparian forest (5.2 %), mountain forest (5 %), dense scrub (4.4 %), and improved grassland (3.6 %). The residential area covers about 14 %. Roads cover 3.4 % of the total area. Surface runoff is responsible for the transportation of large quantities of pollutants that affect the quality of water in the Kuils-Eerste River catchment. The different land-cover types and the distribution and concentration levels of the pollutants are not uniform. Experimental work was conducted at plot scale to understand whether landcover types differed in their contributions to the concentration of water quality attributes emerging from them. Four plots each with a length of 10 m to 12 m and 5 m width were set up. Plot I was set up on open grassland, Plot II represented the neyards, Plot III covered the mountain forests, and Plot IV represented the fynbos landcover. Soil samples analyzed from the experimental plots fell in the category of sandy soil (Sa) with the top layer of Plot IV (fynbos) having loamy sand (LmSa). The soil particle sizes range between fine sand (59.1 % and 78.9 %) to coarse sand (between 7 % and 22 %). The content of clay and silt was between 0.2 % and 2.4 %. Medium sand was between 10.7 % and 17.6 %. In terms of vertical distribution of the particle sizes, a general decrease with respect to the size of particles was noted from the top layer (15 cm) to the bottom layer (30 cm) for all categories of the particle sizes. There was variation in particle size with depth and location within the experimental plots. Two primary methods of collecting water samples were used; grab sampling and composite sampling. The quality of water as represented by the samples collected during storm events during the rainfall season of 2006 and 2007 was used to establish water quality characteristics for the different land-cover types. The concentration of total average suspended solids was highest in the following land-cover types, cemeteries (5.06 mg L-1), arterial roads/main roads (3.94 mg L-1), low density residential informal squatter camps (3.21 mg L-1) and medium density residential informal townships (3.21 mg L-1). Chloride concentrations were high on the following land-cover types, recreation grass/ golf course (2.61 mg L-1), open area/barren land (1.59 mg L- 1), and improved grassland/vegetation crop (1.57 mg L-1). The event mean concentration (EMC) values for NO3-N were high on commercial mercantile (6 mg L-1) and water channel (5 mg L-1). The total phosphorus concentration mean values recorded high values on improved grassland/vegetation crop (3.78 mg L-1), medium density residential informal townships (3mgL-1) and low density residential informal squatter camps (3 mg L-1). Surface runoff may also contribute soil particles into rivers during rainfall events, particularly from areas of disturbed soil, for example areas where market gardening is taking place. The study found that different land cover types contributed differently to nonpoint source pollution. GIS model was used to estimate the diffuse pollution of five pollutants (chloride, phosphorus, TSS, nitrogen and NO3-N) in response to land cover variation using water quality data. The GIS model linked land cover information to diffuse nutrient signatures in response to surface runoff using the Curve Number method and EMC data were developed. Two models (RINSPE and N-SPECT) were used to estimate nonpoint source pollution using various GIS databases. The outputs from the GIS-based model were compared with recommended water quality standards. It was found that the RINSPE model gave accurate results in cases where NPS pollution dominate the total pollutant inputs over a given land cover type. However, the N-SPECT model simulations were too uncertain in cases where there were large numbers of land cover types with diverse NPS pollution load. All land-cover types with concentration values above the recommended national water quality standard were considered as areas that needed measures to mitigate the adverse effects of nonpoint pollution. The expansion of urban areas and agricultural land has a direct effect on land cover types within the catchment. The land cover changes have adverse effect which has a potential to contribute to pollution.
Groundwater resource evaluation and protection in the Cape Flats, South Africa
(University of the Western Cape, 2010) Adelana, Segun Michael Adegboyega; Xu, Yongxin; Mazvimavi, Dominic; Dept. of Earth Science; Faculty of Arts
The analysis of geologic, hydrologic and hydrogeologic data interpreted to give the characteristics of the Cape Flats aquifer showed the quality of groundwater from the aquifer is suitable for development as a water resource. The conceptual model of the Cape Flats sand shows an unconfined sandy aquifer, grading into semi-confined conditions in some places where thick lenses of clay and peat exists. Recharge rates through the saturated zone of the Cape Flats aquifer have been determined by water table fluctuation (WTF), rainfall-recharge relationship, soil water balance and chloride mass balance methods (CMB). Recharge rates using the WTF vary considerably between wet and dry years and between locations, with a range of 17.3% to 47.5%. Values obtained from empirical rainfall-recharge equation (method 2) agree with those of the WTF. Recharge estimates from the water balance model are comparatively lower but are within the range calculated using empirical method 2 (i.e. 87 - 194 mm or 4 – 21% of MAP). These recharge rates also agree with estimates from the series of other methods applied to sites located in the north-western coast of Western Cape and are comparable to recharge rates obtained elsewhere in the world.
Identification and estimation of ecologically relevant flow indices for non-perennial rivers, South Africa
(University of the Western Cape, 2019) Schacht, Bernhard Stuart; Mazvimavi, Dominic
The importance of environmental flows and establishing the balance between hydrological response and ecological functioning of rivers has been globally recognised. Methods for determining environmental flows range from simplistic hydrological methods, to complex holistic approaches. Extensive research has been conducted to understand the dynamics of perennial rivers. However, non-perennial rivers remain among the least studied freshwater systems. Although these rivers only flow during certain periods of the year, these river systems are still of ecological significance. This study therefore aims to characterise the flow regime of non-perennial rivers in an ecologically meaningful way and to assess the spatial variation of these flow attributes. This study identified a subset of ecologically relevant flow indices that provided the opportunity to characterise the flow regime in an ecologically meaningful way, which was based on recommendations of previous studies. Redundancy analysis was used in the study to assess factors that account for the spatial variation of ecologically relevant flow indices of non-perennial rivers. The results identified that mean annual rainfall and the slope equalled or exceeded 90 % of the time were the only catchment characteristics found to be significant at explaining the variance of flow characteristics. The final objective of the study explored methods that can be used to predict flow characteristics in ungauged catchments. Most catchments around the globe are ungauged or poorly gauged, which is a core issue in hydrology.
Influence of multiple uses of water on the sustainability of communally-managed rural water supply systems in Zimbabwe
(IWA Publishing, 2021) Kativhu, Tendai; Mazvimavi, Dominic; Tevera, Daniel
The utilisation of drinking water supply systems for productive uses is not a new practice in Zimbabwe and the world over. This study sought to explore how multiple uses of water, in this case community gardening as a productive use combined with domestic uses influence sustainability of communally-managed rural water supply systems. Using the independent samples t-test, it was noted that community gardening positively influences sustainability. The test was done on institutional, technical, social and financial factors of sustainability. Results showed that there were statistically significant differences in sustainability performance between water points used for multiple uses and those used for domestic uses only. However, it was also noted that using drinking water sources for multiple uses increases the frequency of water use conflicts and water point breakdowns, which negatively impact on sustainability. This means that where water sources are used for multiple uses additional management skills and resources may be required for the water points to be sustained.
Investigating changes over time of annual rainfall in Zimbabwe
(Copernicus Publications, 2010) Mazvimavi, Dominic
There is increasing concern in southern Africa about the possible decline of rainfall as a result of global warming. Some studies concluded that average rainfall in Zimbabwe had declined by 10% or 100 mm during the last 100 years. This paper investigates the validity of the assumption that rainfall is declining in Zimbabwe. Time series of annual rainfall, and total rainfall for (a) the early part of the rainy season, October-November-December (OND), and (b) the mid to end of the rainy season, January-FebruaryMarch (JFM) are analysed for the presence of trends using the Mann-Kendall test, and for the decline or increase during years with either high or low rainfall using quantile regression analysis. The Pettitt test has also been utilized to examine the possible existence of change or break-points in the rainfall time series. The analysis has been done for 40 rainfall stations with records starting during the 1892– 1940 period and ending in 2000, and representative of all the rainfall regions.
Investigating the effects of nutrients and chlorophyll concentrations on the water quality of the Nuwejaars River, Cape Agulhas, Western Cape
(University of Western Cape, 2021) Khungwayo, Agnes Nolitha; Mazvimavi, Dominic
The Nuwejaars River flows into the largest natural freshwater lake in South Africa, Soetendalsvlei, which relies on and interacts with the Nuwejaars River. Therefore, the water quality of the Nuwejaars River plays a role in the health of the surrounding ecosystem. Over a period of three years, concentrations of nutrient constituents, physicochemical parameters, chlorophyll and phycocyanin, were measured in an attempt to investigate the water quality of the river. This study aimed to identify the patterns of nutrients, chlorophyll and phycocyanin down the length of the Nuwejaars River by assessing the physico-chemical parameters, nutrients and chlorophyll concentrations in the surface water to determine the temporal and spatial variations of these parameters, and to examine the relationships between the concentrations of selected nutrients, chlorophyll a and phycocyanin in the river water.
Leveraging Google Earth Engine platform to characterize and map small seasonal wetlands in the semi-arid environments of South Africa
(Elsevier, 2021-07) Gxokwe, Siyamthanda; Dube, Timothy; Mazvimavi, Dominic
Although significant scientific research strides have been made in mapping the spatial extents and ecohydrological dynamics of wetlands in semi-arid environments, the focus on small wetlands remains a challenge. This is due to the sensing characteristics of remote sensing platforms and lack of robust data processing techniques. Advancements in data analytic tools, such as the introduction of Google Earth Engine (GEE) platform provides unique opportunities for improved assessment of small and scattered wetlands. This study thus assessed the capabilities of GEE cloud-computing platform in characterising small seasonal flooded wetlands, using the new generation Sentinel 2 data from 2016 to 2020. Specifically, the study assessed the spectral separability of different land cover classes for two different wetlands detected, using Sentinel-2 multi-year composite water and vegetation indices and to identify the most suitable GEE machine learning algorithm for accurately detecting and mapping semi-arid seasonal wetlands. This was achieved using the object based Random Forest (RF), Support Vector Machine (SVM), Classification and Regression Tree (CART) and Naïve Bayes (NB) advanced algorithms in GEE. The results demonstrated the capabilities of using the GEE platform to characterize wetlands with acceptable accuracy. All algorithms showed superiority, in mapping the two wetlands except for the NB method, which had lowest overall classification accuracy. These findings underscore the relevance of the GEE platform, Sentinel-2 data and advanced algorithms in characterizing small and seasonal semi-arid wetlands

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