Design of urban water distribution systems under water demand uncertainties due to urbanisation.

Abstract

The world is experiencing a high rate of urbanization. Uganda being a developing country, is experiencing a rise in the rate of urbanization, population growth among other uncertain factors. These uncertainties cause difficulties when developing urban water infrastructures that are resilient when these uncertainties unfold. In the current design of UWDS, water demand uncertainties have no clear method of counteracting them. Therefore, need for integrated approaches becomes clearer. The objective of this project was to improve the efficiency of Urban Water Distribution Systems (UWDSs) due to effects caused by uncertain water demand due to urbanization in Uganda today. In this report, the methodology presented here is the decision tree diagram (Flexible Intervention Strategies) as presented by (Basupi, 2013) on the New York Tunnel’s Problem. This methodology generates urban water distribution networks that are adaptable and sustainable under these uncertainties such as those due to Urbanization. This was tested on a case study: Gun hill to Kawempe network that serves Kawempe division. A redesign was undertaken with the current design methods and a comparison was made with the one where the studied approach was used. This was attained with the aid of C++ and EPANET hydraulic solver. It was found out that our network couldn’t supply the required water demand while meeting required hydraulic performance. Therefore, duplicating with larger pipes in sections with suction pressures (Pipes 15 and 24) and reinforcing of pipes whose actual demand exceeded the threshold demand was necessary. For example, replacing DN120 with DN150 and DN120 with DN140 in pipes 24 and 15 respectively.

After comparing duplicating and reinforcing of the affected pipes, with other corrective measures of water demand uncertainty related problems in the network, it turned out that this method was cost effective while meeting the water demand at the required hydraulic performance. Flexible designs are easy to maintain since a single pipe will be duplicated than dealing with many pipes in case of intermittent water supply caused by increase in water demand due to these uncertainties compared to deterministic designs as it is currently done in NWSC.