Dramatic Changes, Big Impact

March 11, 2021
The Importance of flow meter accuracy in the water industry cannot be understated, particularly in today’s climate.

Worldwide, climate change will have a significant effect on the amount of usable fresh water that is available to a rapidly expanding population. Water covers 70 percent of our planet, however only 3 percent is fresh water, of which two-thirds is either frozen or unavailable for use. It has been estimated that 1.1 billion people worldwide lack access to water and 2.4 billion people worldwide are exposed to water-borne illnesses.1

At the current water consumption rate, this is only going to get worse — by 2025 it has been estimated that two-thirds of the world’s population may face water shortages.

With the reduction in the amount of fresh water available due to climate change, it was reported in the New York Times that if current usage trends do not change; the world will only have 60 percent of its fresh water needs by 2030. Coupled with the expected rise in the worldwide population, currently estimated to be at 8.3 billion by 2030, this will result in massive challenges for the worldwide water supply.

Currently agriculture is the largest user of fresh water across the globe, with 70 percent going to this area.2 With food production expected to grow by 60 percent by 2050, the demands on fresh water supply will increase. It has also been estimated that the freshwater needs of manufacturing are likely to increase by 400 percent by 2050, placing further demands on water supplies.

Water Regulation

Currently, there is no national standard within the United States to address water loss. However, the American Water Works Association (AWWA) has developed the M36 Water Audits and Loss Control Programs. M36 uses auditing software that can be utilized by municipalities to try to account for water loss within their networks. An increasing number of regulatory entities are now requiring annual water auditing using the methodology prescribed by the AWWA. This initiative, coupled with the development of Senate Bill 555 in California, which enables the State Water Control Board to place performance standards on water suppliers regarding water loss, could signal the move toward a more performance-based structure for U.S. water utilities assessing water loss.

The lack of a national standard in the U.S. can be compared with the situation in the United Kingdom, where the water regulator Ofwat has recently set stringent targets on leakage reduction for all of the U.K. water utilities. In the next five years, Ofwat expects these utilities to have reduced overall leakage by 16 percent.

Taking Action

There will be enough water to meet the world’s growing needs, but only by dramatically changing the way water is used, managed and shared. Therefore, action is required now.

Groundwater is the most important source of fresh water, as around the world more than two-billion people receive their water supply via groundwater sources. However, the impact of climate change is being felt on these sources, and in many regions, water is being removed faster than it is being replenished. Overall water quality is also affected by seawater intrusion into the aquifers, resulting in large concentrations of undesirable minerals — a situation which is totally unsustainable. Therefore, knowledge of the amounts of water being abstracted are required to manage the levels of water within the environment. Accurate knowledge requires accurate flow metering.

If the levels of global non-revenue water (NRW) could be reduced by one-third, this would provide water savings sufficient to supply 800 million people, and offer a financial benefit of around USD $13 billion per year.3 The global volume of NRW has been estimated to be 346 million m3/day, equating to 126 billion m3/year. If valued conservatively at USD 0.31 m3, that six-billion gallons of treated water is lost every day. In times of climate change and water scarcity these vast volumes of NRW could go a long way to help meeting the extra demands that will be placed on the water utilities.

With the demands being placed on fresh water supply, coupled with expanding populations, the complete coverage of a water service is still a global challenge. The reduction of NRW can provide numerous benefits, including reducing operating costs, better water resource efficiency, and an increased water supply at a fraction of the costs associated with the production of new water production facilities. However, it is important to recognize when water leakage is actual leakage and not caused by inaccuracies in the flow meter measurements.

Water meters, both at the source and at the service connection, are therefore very important for all aspects of water supply operations and management as they make accurate water auditing possible. Both small and large meters are therefore essential for effective, economic and sustainable water management. However, unlike small meters, whose accuracy can be easily validated at little cost by placing them on a traceable flow rig, there has been very little independent testing of large diameter meters, as their size significantly increases the cost of any calibration arrangements. This has led to a gap in industry knowledge regarding the accuracy and performance of larger diameter flow meters.

What Can be Done?

TÜV SÜD National Engineering Laboratory is currently working with partners including Arup, WRc and Severn Trent Water to develop a wide-ranging, global Joint Industry Project (JIP) to investigate the meter uncertainties associated with large diameter water flow meters.

The core objective of the project is to is to improve the optimization of water management including the reduction of leakage through more accurate flow measurement. This comprises two sub-objectives:

  • To understand the impact of physical/technological/environmental/installation and age effects on large diameter flow meter uncertainty.
  • To disseminate any knowledge obtained from this work program for the benefit of the global water industry.

Work has been undertaken previously to investigate the effect of flow distortions in large diameter pipelines. A computational fluid dynamics (CFD) study undertaken on a 600 mm main, with a fluid velocity of 1 m/s, and two 90-degree bends in offset planes4 showed that the fluid flow profile does not become acceptable until 96 D downstream of the disturbance. The effect on the fluid flow profile in large diameter pipes is extremely important, especially when considering flow measurement. Therefore, basic research is required, using both physical models and CFD, in order to determine how different upstream disturbances can affect the accuracy and performance of large diameter flow meters.

To achieve a robust and holistic picture of the factors affecting the accuracy of large diameter flow meters, the JIP will see a significant program of testing carried out on a range of flow meters. The data generated will represent an unrivaled piece of work — looking at how the uncertainties of large diameter water flow meters are affected by pipe size, flow disturbance and placement and fluid velocity.

This JIP will aim to fill industry knowledge gaps, update existing industry guidance, and investigate how the accuracy of large flow meters is affected by upstream flow disturbances and fluid velocity. A better understanding of the flow of water into the distribution network will lead to more accurate water balances and leakage determination while supporting the water utilities in their quest to meet the regulatory mandated leakage reduction targets and ensure more sustainable and cost-effective water management. WW

1. World Wildlife Fund. Water Scarcity. Washington, DC, 2014. Accessed September 10, 2020.
2. Arup. Water and the Circular Economy, November 2019.
3. Liemberger, R, and A Wyatt. Quantifying the Global Non-Revenue Water Problem. Water Science & Technology. July 2018.
4. Godley, A., and M. Willmott. DMA and Large Diameter Meters — Some Guiding Principles, IWA Waterloss Webinar Series, May 29, 2020.

About the Author: Carl Wordsworth is head of the water sector at TÜV SÜD National Engineering Laboratory, a world-class provider of technical consultancy, research, testing and program management services. Part of the TÜV SÜD Group, it is also a global center of excellence for flow measurement and fluid flow systems and is the UK’s Designated Institute for Flow Measurement.

About the Author

Carl Wordsworth

Carl Wordsworth is Head of Water Sector at TÜV SÜD National Engineering Laboratory, a world-class provider of technical consultancy, research, testing and program management services. Part of the TÜV SÜD Group, it is also a global center of excellence for flow measurement and fluid flow systems and is the UK’s Designated Institute for Flow Measurement