For many years water utility leakage engineers have been dividing large distribution zones into smaller areas (or DMAs) as a first step in localising potential areas of leakage.
However, the DMA philosophy is not supported by all water company practitioners. With the recent surge in innovative monitoring technology, are DMAs still necessary? Let us look at the alternative technologies for monitoring networks without closing boundary valves, or, if large DMAs are already in place, some low-cost innovative flow metering technologies for sub-dividing them into smaller areas.
DMAs - The Benefits
The technique of night flow monitoring to identify areas of leakage is considered to be the major contributor to cost-effective and efficient leakage management. It is a methodology which can be applied to all networks. Even in systems with supply deficiencies, leakage monitoring zones can be introduced gradually. One zone at a time is created and leaks detected and repaired, before moving on to create the next zone. This systematic approach gradually improves the hydraulic characteristics of the network and improves supply. Leakage monitoring requires the installation of flow meters at strategic points throughout the distribution system, each meter recording flows into a discrete district which has a defined and permanent boundary. Such a district is called a District Metered Area (DMA).
Evolution of the DMA Methodology
While working for the UK Water Research Centre (WRc) in 1982, I was responsible for designing what were almost certainly the first two DMA systems to be introduced to the UK water industry, and certainly the first in the world. Known then as ‘district metering systems’ the first was in the City of Plymouth (now part of South West Water) and the second was a telemetered system for a small water company to the west of London, Rickmansworth Water Company (now part of Three Valleys Water).
The experience gained from designing and installing these systems, and later using them to guide leakage detection activities provided essential guidelines on DMA management for other leakage practitioners. Based on these practical experiences, from using the technology available at the time, I wrote two WRc reports in the mid 1980s: District Metering: Part1 -System Design and Installation’ and ‘District Metering: Part 2 – System Operation’. These formed the basis for a number of manuals and books that were produced in the years that followed.
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