3-2-2 Formation of DMA and its use in reducing NRW

Summary

This chapter focuses on the formation and management of District Metered Areas (DMAs) to reduce non-revenue water (NRW). It highlights how efficient DMA management can be achieved by analyzing water balance data for pipeline maintenance and identifying leakage. The chapter discusses DMA size, with examples from Osaka and Tokyo, and its role in leakage detection and prevention. It covers methods for measuring minimum night flow, challenges under intermittent water supply conditions, and the impact of water pressure and quality. The use of flow meters and leakage prevention work is emphasized as key to effective NRW reduction.

Takeaways

• 😀 DMAs (District Metered Areas) are crucial for reducing Non-Revenue Water (NRW) by efficiently managing and monitoring water usage in smaller areas.
• 😀 DMAs enable the accurate collection and analysis of water balance data, aiding in targeted pipeline maintenance and renewal efforts.
• 😀 Effective NRW reduction is verified on a small scale in DMAs, making it easier to plan repairs and maintenance based on real-time data.
• 😀 When accidents or disasters occur, DMAs minimize water loss and shorten the period of water outage by isolating affected areas quickly.
• 😀 The size of a DMA is typically between 500 to 3,000 houses, but it can vary based on population, leakage status, and land use.
• 😀 Osaka City used DMAs with sizes of 1 to 3 km of surveyed water pipes, while Tokyo's DMAs typically cover areas with around 700 to 2,400 households.
• 😀 Each DMA has its own water flow meter, and multiple DMAs in Tokyo are grouped into sectors, each with a sector flow meter.
• 😀 Leakage prevention work is carried out DMA by DMA, prioritizing areas with higher night flow amounts for faster leak detection and repair.
• 😀 Portable and insertion-type electromagnetic flow meters are used to measure the night flow amount, helping calculate water loss efficiently.
• 😀 In areas with intermittent water supply, estimating leakage is challenging due to water storage practices, but sampling or rotating 24-hour supply can help measure night flow accurately.
• 😀 DMA formation can lead to changes in water pressure, which in turn affects leakage levels; water quality might also deteriorate due to closed boundary valves, but solutions like pipe washing can mitigate this.

Q & A

What is the primary purpose of forming District Metered Areas (DMA)?

The primary purpose of forming DMAs is to efficiently reduce Non-Revenue Water (NRW) by collecting and analyzing water balance data for each DMA. This helps in identifying leakage issues, planning pipeline maintenance, and verifying the effectiveness of various NRW reduction measures.

How does DMA formation help in case of accidents or disasters in the water supply system?

DMA formation helps minimize water loss and shortens the period of water outage during accidents or disasters by isolating the affected DMA and ensuring quick restoration of water supply.

What is the typical size of a DMA in Osaka and Tokyo?

In Osaka, each DMA typically covers an area of 500m to 1 km² with approximately 2,000 households. In Tokyo, the average DMA size covers around 700 households.

What are the key factors considered when determining the appropriate size of a DMA?

The appropriate size of a DMA is determined based on factors such as the status of leakages, population density, and land use in the area.

How is leakage prevention work carried out in DMAs?

Leakage prevention work is carried out DMA by DMA. The process begins by measuring the minimum night flow, identifying DMAs with high night flow, and prioritizing them for leakage detection and repair. The work continues until the leakage ratio reaches the target, after which it moves to the next DMA.

What equipment is used for measuring night flow in DMAs?

Portable water flow meters and electromagnetic flow meters are used to measure night flow in DMAs. These meters are installed in the pipeline, and the night flow is calculated by subtracting the outflow from the inflow.

What are some challenges in measuring leakage in DMAs under intermittent water supply conditions?

Measuring leakage in DMAs under intermittent water supply is challenging because many water users store water during the supply periods. If water meters are not installed, it may be necessary to sample water usage from representative users or rotate the supply periods for each DMA.

What impact does water pressure have on leakage in DMAs?

Water pressure directly affects the leakage amount in DMAs. If the water pressure changes due to DMA formation or an increase in water supply capacity, the leakage amount may also change accordingly.

How does DMA formation affect water quality, and how can it be addressed?

DMA formation can lead to water quality issues, especially in dead-end areas where boundary valves are permanently closed. This can cause a decrease in water quality, such as residual chlorine. Solutions include pipe washing and installing drainage equipment near these boundary valves.

What is the role of water flow meters in DMA management?

Water flow meters are used to monitor the inflow and outflow of water in a DMA. By measuring these flows, water utilities can calculate the minimum night flow, which is a key indicator for detecting leaks and assessing the effectiveness of leakage prevention efforts.