A study of the impact of water supply network expansions on water network hydraulics: a case study of zone 8, Kampala Water

Abstract

The National Water and Sewerage Corporation (NWSC) in a drive to provide wide water supply coverage and to maximise profits has increased the number of customer connections through a massive network expansion. At the same time, service levels have drastically dropped, with customers receiving intermittent water supply, and in many cases, not at all. This background prompted this research with the chief aim of studying the hydraulic impact of the water supply network extensions. Specifically, the research was aimed at studying the effects of the expansions on pipe pressures, velocities and flows and suggest remedial measures; and recommend the extent to which extensions should be made in order to maintain satisfactory hydraulic properties. The methodology involved the assessment of the water supply situation before and after major extensions were made. Consumption patterns were generated from the block maps and water audits of the GIS records of Kampala Water. A simulation of the network was carried out using the EPANET-2 software. The modeling process involved data collection, system operation and monitoring, network schematization, model building, model testing and the analysis of the problem. Most notably, it was found that pressure zones are not well marked out and transmission mains were no longer functionally differentiated from distribution mains. Pressures were found to fall with more extensions being made. Head losses were also found to be high. Velocities and flows in the pipes reduced with more extensions. The conclusions drawn from the study show a strong relationship between the network extensions and the reduce service levels. Recommendations have therefore been made and include among others, carrying out careful hydraulic considerations before any extensions are made, encourage installation of tanks in consumer units to act as reservoirs, marking out and respecting hydraulic zones, maintaining the transmission mains intact, rationalizing the network and installing boosters where necessary.