A thesis submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Doctor of Philosophy. Johannesburg, May 2016. / This thesis presents work on four problems identi ed in the Zomba Water Distribution
Network. The research was carried out on the existing network infrastructure with the aim
of improving e ciency by reducing Unaccounted-For Water (UFW). The rst challenge
was to develop a demand model for the city based on its in
uencing factors: daily and
seasonal
uctuations as well as population dynamics. The model was to capture demand
patterns for short-term, medium-term to long-term time periods, thereby becoming an
important input factor into decision making. The developed model may be employed
to generate demand which can be input into the city's 10 year infrastructure expansion
plan. The second problem was to explain why houses built too close to tanks are at risk
of inconsistent water supply. It was found that the requirement of observing the tank
elevations, helv, had been violated. As a result, the discontinued supplies occurred. Once
the required tank elevation helv had been established, an extra increase in the elevation
so as to accommodate a larger population was determined to be on the order of one
centimeter. Third problem was to explain the continued mains pipe failures observed in
the network. It was established that the main cause was the hammering e ects started
through the process of manually closing
ow control valves (FCVs) tted next to tanks.
A possible remedy was to rather t the FCVs at joint nodes and not at the tanks. This
was estimated to greatly reduce the hammering e ects, eventually turning them into
minor head losses due to elbow bends. Finally, a structural approach to designing tanks
that optimize the use of gravity is presented. This is an input into the infrastructure
expansion planning of the city. Regardless of any design shapes they may take, tanks
with height-radius, h=r, ratio of less than 1 exhibit diminished, as opposed to increased,
height changes with demand changes. Such a property would ensure consistency in the
pressure at the tank, allowing for delivery of the demanded load. / GR2016
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:wits/oai:wiredspace.wits.ac.za:10539/21202 |
| Date | January 2016 |
| Creators | Fodya, Charles |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | Online resource (89 leaves), application/pdf, application/pdf, application/pdf |
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