Themba Gumbo - Academia.edu (original) (raw)

Papers by Themba Gumbo

Phosphorus (P) resources globally are considered limited. P originates from a mined non-renewable... more Phosphorus (P) resources globally are considered limited. P originates from a mined non-renewable rock, therefore its presence in the urban-shed demonstrates the impact of urbanisation and the anthropogenic influences on nat ural cycles of material flow. Any recycling of P is therefore becoming increasingly important. In passing through the linear urban system P is mobilised from particulate to soluble forms. With the present level of nutrient losses from urban water management into the aquatic environment (leading to adverse health and ecological impacts) commitment to urban or peri -urban ecological agriculture (without synthetic fertilisers) offers an attractive solution to the management of urban organic “wastes”. The ma cro-nutrients stemming from human metabolism contained mainly in urine are of particular interest. Sustainable “Urban Drainage System” (UDS) technology should support closing of cycles of natural resources such as nutrients in urban water management. This paper ...

An integrated approach to water resource management is required to balance water for food and nat... more An integrated approach to water resource management is required to balance water for food and nature but also to unlock pathways to sustainable development. The semiarid Limpopo basin is a hotspot area in terms of scarcity of water for food as well as poverty. Translating IWRM from concept to action here poses a great challenge. Water institutions adopt a conventional blue water framework, focusing on water supply for irrigation, domestic and industrial use. In semi-arid regions such a water resource strategy has its limitations, though. Blue water resources for irrigation are over-committed, while the bulk of agricultural produce sustaining lives of resource poor farmers originates from green water flows in rainfed crop and livestock production.

Schriftenreihe des Vereins für Wasser-, Boden- und Lufthygiene, 2000

The Harare metropolis in Zimbabwe, extending upstream from Manyame Dam in the Upper Manyame River... more The Harare metropolis in Zimbabwe, extending upstream from Manyame Dam in the Upper Manyame River Basin, consists of the City of Harare and its satellite towns: Chitungwiza, Norton, Epworth and Ruwa. The existing urban drainage system is typically a single-use-mixing system: water is used and discharged to "waste", excreta are flushed to sewers and eventually, after "treatment", the effluent is discharged to a drinking water supply source. Polluted urban storm water is evacuated as fast as possible. This system not only ignores the substantial value in "waste" materials, but it also exports problems to downstream communities and to vulnerable fresh-water sources. The question is how can the harare metropolis urban drainage system, which is complex and has evolved over time, be rearranged to achieve sustainability (i.e. water conservation, pollution prevention at source, protection of the vulnerable drinking water sources and recovery of valuable materia...

Water Science & Technology, 2009

Kibera, located in Nairobi, Kenya is one of the largest (235,000 inhabitants) low-income areas in... more Kibera, located in Nairobi, Kenya is one of the largest (235,000 inhabitants) low-income areas in East Africa. Surface waters in Kibera show high pollution levels with respect to SRP (soluble reactive phosphorus; range: 2–10 mg P/L), coming from the uncontrolled wastewater discharges in the area. The different P production and consumption values in Kibera were estimated using interviews (155 interviewed) as well as detailed P house-keeping for five representative families. The results show that highest P consumption comes from food, in particular cereals. Highest P production came from urine (55% of the total) and faeces (31%), with relatively lower contributions from grey water and solid wastes. The overall P budget in Kibera amounted to around 9 × 103 kg P/month. This is equivalent to 0.47 g P/person yr, both for P production and consumption, with a relative error of 20%. Comparing with the estimated P outflows via the Kibera surface waters, around 65% of the P produced in Kibera ...

The Challenge of Integrated Water Resource Management for Improved Rural Livelihoods: Managing Ri... more The Challenge of Integrated Water Resource Management for Improved Rural Livelihoods: Managing Risk, Mitigating Drought and Improving Water Productivity in the Water Scarce Limpopo Basin: Integrated Water Resources Management (IWRM) is a systems approach ...

This book discusses needs related to capacity development for water resources management, includi... more This book discusses needs related to capacity development for water resources management, including water supply and sanitation, in the context of the green economy. It showcases theoretical and practical approaches with proven success. Most contributions come from members and partners within the interagency mechanism, UN-Water. The 11 case studies in this book range from innovative design and delivery of capacity development programs related to water in the green economy, market mechanisms, and quality control procedures supporting capacity development success towards the practical implementation of programs to enhance individual and institutional capacity

Physics and Chemistry of the Earth, Parts A/B/C, 2006

Physics and Chemistry of the Earth, Parts A/B/C, 2004

Physics and Chemistry of the Earth, Parts A/B/C, 2002

Often planners and engineers are faced with various options and questions in storm drainage netwo... more Often planners and engineers are faced with various options and questions in storm drainage network design e.g. flow pattern, direction, runoff quantity and therefore size of drain, or scenario after a road, airfield or building has been constructed. In most instances planning without drainage in mind has caused failure or extensive damage to property including the storm water drains which

Hydrology and Earth System Sciences, 2012

Physics and Chemistry of the Earth, Parts A/B/C, 2003

The combination of water demand management and cleaner production concepts have resulted in both ... more The combination of water demand management and cleaner production concepts have resulted in both economical and ecological benefits. The biggest challenge for developing countries is how to retrofit the industrial processes, which at times are based on obsolete technology, within financial, institutional and legal constraints. Processes in closed circuits can reduce water intake substantially and minimise resource input and the subsequent waste thereby reducing pollution of finite fresh water resources. Three industries were studied in Bulawayo, Zimbabwe to identify potential opportunities for reducing water intake and material usage and minimising waste. The industries comprised of a wire galvanising company, soft drink manufacturing and sugar refining industry. The results show that the wire galvanising industry could save up to 17% of water by recycling hot quench water through a cooling system. The industry can eliminate by substitution the use of toxic materials, namely lead and ammonium chloride and reduce the use of hydrochloric acid by half through using an induction heating chamber instead of lead during the annealing step. For the soft drink manufacturing industry water intake could be reduced by 5% through recycling filter-backwash water via the water treatment plant. Use of the pig system could save approximately 12 m 3 /month of syrup and help reduce trade effluent fees by Z$30/m 3 of ''soft drink''. Use of a heat exchanger system in the sugar refining industry can reduce water intake by approximately 57 m 3 /100 t ''raw sugar'' effluent volume by about 28 m 3 /100 t ''raw sugar''. The water charges would effectively be reduced by 52% and trade effluent fees by Z$3384/100 t ''raw sugar'' (57%). Proper equipment selection, equipment modification and good housekeeping procedures could further help industries reduce water intake and minimise waste.

The question posed in this paper is: why is the concept of water demand management rarely impleme... more The question posed in this paper is: why is the concept of water demand management rarely implemented on the ground? To answer this question the paper presents data on the water supply situation in the City of Mutare, Zimbabwe. It describes Mutare’s water infrastructure, the patterns of water use during the period 1980–2000; and our attempts to identify and quantify water losses in the system. Suggestions are made how these losses can be reduced, which would involve relatively modest resources. The question is then asked why these measures have not yet been taken. The paper contrasts this to the Pungwe scheme, a new water supply project of huge proportions which was conceived and implemented fairly quickly. The fact that water is a vital yet finite and fugitive resource explains why powerful water coalitions may emerge between engineers, financiers and politicians. It is the experience from Mutare and elsewhere that such coalitions tend to favour supply-side solutions to water scarc...

Integrated water resource management (IWRM) research for mitigating drought

Global fertiliser use has soared from less than 14 million tonnes in 1950 to about 145 million to... more Global fertiliser use has soared from less than 14 million tonnes in 1950 to about 145 million tonnes today. Consumption is now stable or declining in the industrialised countries but demand is still rising in the developing world. By 2025, it is estimated to reach 250 million nutrient tonnes per year. The major driving force is increasing food production, driven in turn by increasing human population and the growing demand for livestock products, particularly in developing countries. Cereals, rice, wheat, maize etc are the main source of nourishment for the world’s population and currently around 50% of the nutrients, including phosphate, used in agriculture, are used in cereal production. Figure 1 shows the breakdown of global fertiliser consumption in terms of the macro-nutrients N (Nitrogenous fertiliser), P (Phosphate based fertiliser) and K (Potash fertiliser) as from 1961.

Mufakose, a high-density suburban area, located within the city of Harare in Zimbabwe, is investi... more Mufakose, a high-density suburban area, located within the city of Harare in Zimbabwe, is investigated with respect to the performance of the water and wastewater systems. Integrated urban water management entails the holistic management of all water fluxes in an urban-shed and identifying the interactions between the different components. Like many suburbs in Harare Mufakose has experienced profound densification due to urban-rural migration over the last 20 years. There is great concern on the performance of the water supply and wastewater evacuation system. Currently with a population of around 100 000 inhabitants and 9 400 metered stands, Mufakose has experienced a high degree of impermeabilisation due to construction of backyard rooms and outhouses to accommodate the increased population per stand. Mass balancing was used to assess the functioning of the system based on original design criteria. Only quantitative assessment is taken into account. Based on measurements of rainfa...

This paper attempts to highlight how implementation of the integrated water resource management a... more This paper attempts to highlight how implementation of the integrated water resource management approach can reduce livelihood risk, either as a basis for an agricultural intervention, or as an essential planning tool. Three groups of studies are showcased. The first examines conservation agriculture and rainwater harvesting; the second evaluates the productivity, impact and sustainability of the current widespread distribution of low-head drip kits for irrigation at household level and the third case study considers aspects of climate change and livelihood risk. The basic principle illustrated in each of these three studies is that water in agriculture (although this is true in general) is best managed by considering the water cycle. This issue arises because the water cycle is a complex system and the implementation of a livelihood intervention that involves water use – whether in rainfed agriculture, irrigation, domestic supply or elsewhere – has to consider the impacts of that i...