Updated: Dec 6, 2019
District Metered Areas
Increasing population and urbanization in the past few decades has led to exponential increase in the use of water. This increase in the demand calls for water networks to be highly efficient as well as highly measurable.
District Metered Areas (DMAs, also called sectorisation) is one of the most promising methods of improving the water supply qualitatively and quantitatively. Non-Revenue Water, commonly known as NRW is a big challenge before the public bodies who supply water to a cluster of users. In this article, we will study about DMAs, how they help to improve water supply qualitatively and quantitatively and how they can help us reduce the NRW.
What is a District Metered Area?
As a normal practice, water from one Elevated Storage Tank is supplied to a specific region. If one such region is broken down into multiple smaller sub-regions where we can monitor water input to and consumption in each of such sub-regions, these sub-regions will be called District Metered Areas.
In short, district metered areas are small clusters of water users with a provision to individually monitor the water supplied and consumed. Each DMA can be isolated from others in two manners - either with use of isolation valves at its boundary or by cutting off the pipes connecting that DMA to other DMAs.
Counter to the popular belief, setting up DMAs is equally easy for urban locations where users are densely located as well as rural areas where a small number of users are sparsely spread over a large geographical area.
How are DMAs formed?
Multiple factors are considered while forming DMAs in an existing network. Following are some of the criteria or considerations while forming DMAs:
Number of users or connections: One DMA generally has between 1000 to 2500 connections. For DMAs larger than this, finding out NRW would be difficult whereas for DMAs smaller than this, the cost of monitoring and isolation equipment will go up beyond economic feasibility.
Topography: It is recommended to use normally available topographical features such as rivers, lakes, terrain variations and even main roads to form DMAs as they will ensure ease of isolation.
Isolation and inter connectivity: Though the DMAs should be well isolated from each other DMAs for precision in measurements, they should also be interconnected using Isolation Valves (initially set as closed and can be opened while responding to some emergency/ pipe break cases) so that water from one DMA can be fed into other for better distribution.
Cost of setting up DMAs: Cost of setting up DMAs will primarily depend upon the cost of isolation and metering equipment required. For the isolation purpose, standard isolation valves are used whereas for the metering purpose, flow meters are used. DMAs should be formed in such a manner that, minimum number of valves and flow meters are required to achieve desired results.
Slopes and elevation: Ideally, a DMA should comprise of uniform terrain. If a DMA has lots of terrain variations, providing water to all users at uniform pressure would be difficult.
Pros and Cons of having DMAs:
DMAs are highly evolved concept, accepted widely across the globe as a standard practice. The only con of having DMAs is the higher initial costs required for setting them up. But, if one considers numerous benefits out of them, in long run, the savings achieved beat the initial investment with a huge margin. Following are some of the benefits of DMAs:
Tracing down NRW: NRW, or Non-Revenue Water is total water which is used or wasted but not billed. Illegally used water, leakages, unauthorized connections add to NRW. Forming DMAs and periodically analyzing water consumption and tallying it with revenue can give an insight into the quantum of NRW. Tracing down the causes of NRW and eliminating them, significantly impacts the profitability of water distribution networks.
Improved quality and consistency of water supply: DMAs also ensure uniform and consistent water supply to the users. Thoughtfully designed DMAs, which also consider terrain variations, will lead to water distribution at uniform pressure.
What are Pressure Managed Areas?
Pressure Managed Areas (PMAs) are DMAs which have controlled pressures. Typically, a Pressure Regulating Valve (PRV) is installed on the Feeder to the DMA at its entry point. This PRV arrangement ensures equitable pressures within each DMA of an operational zone.
The PRV can be set manually to a static pressure setting or can be installed with a Pilot which dynamically operates and sets the PRV based on the downstream diurnal/ weekly or monthly demand fluctuations of the consumers within every DMA.
Dynamic Pressure Management Systems
Dynamic Pressure Management System (DPMS) is an arrangement of PMAs, which sets the PRV to adequate pressure setting during high demand hours and reduces the pressure within the DMA during low demand hours. During the low demand hours (night hours) the pressure within the DMA shoots up, causing increased leakage through the existing breaks and ruptures on pipeline. As the PRV reduces the pressure, the resulting leakage is also reduced. This has emerged as a popular practice to control NRW at DMA Level and is quite successful.
Food for Thought:
What do you think would be the challenges while implementing DMAs in sparsely populated, widely spread rural locations, comment below?
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