Challenge

The unregulated siphoning of water, non-standard construction practices and the informal creation of spaghetti lines along narrow, unplanned roads created an ineffective network with low water pressure a common problem.

Leakage in the distribution network also constituted a huge loss of water and income for the National Water Supply and Drainage Board (NWSDB). The combination of old pipe systems, inaccurate billing and ineffective water supply had caused elevated levels of non-revenue water (NRW). The client target was to reduce the NRW figure from 50% to 17.1% in Colombo City.

SMEC commenced the project with limited baseline data available with no pipeline network mapping or as-built drawings from which to diagnose a solution. The meter network had proven unreliable and therefore SMEC needed to undertake extensive site testing to assess flow measurements and build an understanding of usage across the network.

Solution

It was decided to implement a District Metering Area (DMA) management concept and utilise NRW management concepts to assess the efficacy of the system. The District Metering Areas enable the client to accurately monitor inlets.

This process included the design and supervision of new water meter installations, active leak detection systems, commissioning of new pipes and decommission of unnecessary lines.

The DMA has only one inlet and with boundary valves for emergency feeding. Monitoring these inlets along with System Input Volumes (SIV) was suggested to record accurate inflows.

As part of this project, installation of electromagnetic flowmeters for DMA inlets and ultrasonic flowmeters for SIV inlets were done for the first time in Sri Lanka. An Active Leak Detection programme was implemented where the DMAs are monitored daily to identify leaks in DMAs.

The SMEC team completed supervision of the DMA construction, including monitoring and management. The scope also included:

• Monthly DMA and NRW calculations
• Review of Pressure Zero Tests and Step Test reports
• Night Flow Assessments for NRW Management
• Supervision of new water pipe laying
• Design and supervision of new flow meters (District Meters such as Electromagnetic and Ultrasonic meters and Service Connections)
• Decommissioning of old pipes
• Review and verification of the Bill of Quantities during construction
• Update and validate Geographic Information System (GIS) of distribution system and water supply components, storing attributes and images of infrastructure including location coordinate
• Construction of facilities such as Meter Test Bench building and training centres

Impact

The project team worked together to establish a convenient decentralised system (DMA) to monitor NRW in Colombo City, resulting in a rehabilitated and improved network. Accurate consumption billing is now obtained through accurate water metres and improved accessibility to these metres. Unnecessary SIVs to the city were abandoned, and an online monitoring platform for DMA and SIV inputs was set up.