Management of unaccounted -for-water in the greater colombo water supply Distribution system.

Abstract

Water losses in the water distribution system is a common phenomenon experienced by water supply facilities all over the world. Unaccounted-for-Water (UFW) is the difference between the quantity of water produced and the total quantity of water consumed in the water supply system. UFW cannot be eradicated from a water supply system, as some components of it cannot be avoided, but it could be minimized and maintained at a low level, by proper management of operations and controls in the system. Non-Revenue-Water (NRW) is the difference between the quantity of water produced and the quantity which brings in revenue to the water authority. Sometimes NRW is used instead of UFW, but they are not identical, as there are some components which are not common to both these terms. In this study, the problem of UFW and NRW in this Greater Colombo Water Distribution System was investigated with respect to the various components. Having identified the most significant components theoretical and field studies were carried out to develop management techniques to effectively reduce these significant components of UFW. The Study concluded that the throttling of standposts to a limit that did not produce a noticeable reduction of pressure at the consumer’s tap was one of the most effective means of reducing NRW. Replacement of defective and unreliable water meters, particularly the turbine type meters, and the introduction of a caretaker system for the distribution system were also shown to be effective management techniques. The Minimum Night Flow Test, which was carried out for a section of the distribution system in this study is recommended as a suitable monitoring tool for UFW. Further study is needed to develop an action plan for the successful control of illegal consumption.