Climate change and global population increase are two of the main issues currently being faced by the global water industry. The expected future demands on freshwater use will require a completely new way of thinking about water to be embraced, if the world is to meet these future challenges.

Globally, there are few resources as essential as water. As the fluid of life, water is needed and used by every single person on the planet, but with the growing impacts of climate change being felt across the worldwide water sector, action is required now in order to reduce demand, increase supply and apply the principles of a circular economy to the way water is managed and shared. If we are to meet the expected future demands on freshwater resources this will require a dramatic change in the way the world thinks about freshwater and how it is measured.

Metering is essential for measuring water usage and managing water supplies. Most water meters around the world are small and primarily used to record domestic water consumption, but larger meters, whilst smaller in number, measure an equivalent volume of water and are key to managing both resource and demand. It is principally through the use of larger meters that we quantify how much water is being abstracted from underground aquifers, rivers and other water bodies to provide the cooling water for all significant power plants, or clean water supplies to our cities. Both small and large meters are therefore essential for effective, economic and sustainable water management. However, unlike small meters which can be easily validated at little cost by calibrating them on a traceable flow rig, there has been very little independent testing of large diameter meters due to the sheer size and cost of any calibration arrangements. This has led to a gap in our knowledge of the uncertainty performance of this key meter classification.

“if current usage trends do not change the world will only have 60% of its freshwater needs by 2030”

With the expected reduction in the amounts of freshwater available due to climate change; it has been estimated that if current usage trends do not change; the world will only have 60% of its freshwater needs by 20301; coupled with the expected rise in the worldwide population; currently estimated to be at 8.3 billion by 20302; and combined with the increase in urbanisation this will result in massive challenges for the worldwide supply of fresh water.

The need for accurate measurement on large diameter transmission (trunk) mains is of national importance to the UK, to optimise water resource, accurately estimate leakage and calculate the water balance across the water distribution system. It is also a significant issue in other countries, e.g. Australia, USA and South Africa. If an accurate and reliable approach can be developed as ‘National and International Best Practice’, this would be of significant global importance as the pressure to optimise water resources increases with the impacts of Climate Change.

Independent research3 has shown that pipe diameter can have a significant effect on the accuracy of flow meters. This, coupled with the importance of flow disturbances in large pipes, results in the need for independent testing of flow meters in large pipes, to investigate these effects and how they affect the flow meter uncertainty.

In the next five years, one UK water company intends to replace some of their largest meters. The top ten meters they have identified for replacement have on average over 26 years of service and have recorded over 3.5 trillion litres of water. These meters are only replaced once in a generation. Therefore, ensuring that they purchase the right meter, utilising the correct technology (e.g. electromagnetic, ultrasonic, insertion probe) and placing it in the right location is essential as it may be more than a quarter of a century before these meters are exchanged again. Understanding how meters perform on a 1,000 mm diameter pipe will be critical in helping this company and the many water utilities like it find an optimised solution.

With regulators requiring leakage reductions of 16% over the next five years, throughout the UK water companies are carrying out more and more transmission (trunk) main balances to locate bursts, leakage or non-revenue water. Large diameter metering is a key element for obtaining accurate and auditable results but can be very expensive. Several water companies in the UK can cite examples of installation costs alone that are over £100,000 ($130,000 USD) for just one large meter, with meters costing between £10-30K depending on the technology. Understanding which technology provides most value for money is essential for increasing both operational and financial efficiency.

Whilst the numbers of large diameter water flow meters (LDWFs) are limited in the UK, the volumes of water passing through them are large; two UK water companies estimate that 25% of their daily flow passes through meters of 1000mm or greater. This equates to daily flows in the region of 500 million litres per day per company. In order to allow the water companies to provide accurate water balances and to reduce Non-Revenue Water (NRW) to a minimum, accurate flow measurements are required, as even small inaccuracies in the meter readings can lead to large volumes of water being wrongly accounted-for.

Water – the future Worldwide, climate change is going to have a significant impact on the amount of useable freshwater that is available to a rapidly expanding population. Water covers 70% of our planet, however only 3% of this water is fresh water and of this, two-thirds is either frozen or unavailable for use4.

It has been estimated that currently:

• 1.1 billion people worldwide lack access to water
• 2.7 billion people find water scarce for at least one month per year
• 2.4 billion people worldwide are exposed to water-borne illnesses

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.

Currently agriculture uses the largest volume of fresh water, with 70% of the resource being used in this area5. With food production expected to grow by 60% by 2050 to meet the needs of an increasing population, the demands on freshwater supply are only going to increase. It has also been estimated that freshwater manufacturing needs are likely to increase by 400% by 2050, placing further stresses on the freshwater supply. “freshwater manufacturing needs are likely to increase by 400% by 2050, placing further stresses on the freshwater supply”

To meet these needs, action is required now. It will be necessary to reduce demand and increase supply in order to meet future freshwater requirements. There will be enough water to meet the worlds growing needs, but only by dramatically changing the way water is used, managed and shared5.

Potential ways that this can be undertaken include:

• Applying circular economy principles to the water sector5
• Unaccounted for Water (UFW) reduction, Asset Management Plan Period (AMP7) already calls for a 16% reduction of leakage over the next five years
• Reduction of personal water consumption – in the UK this currently stands at 141 litres per person per day in the UK6
• Increase the use of water transfers between areas of high supply and demand
• Building new reservoirs
• Building new desalination plants

In the UK, climate change is expected to have a major impact across the water sector in the coming years; the expectation is for hotter, drier summers, and subsequent water shortages. It has been estimated that by 2050 the amount of water available could be reduced by 10 – 15%, this means a higher drought risk. Some parts of the UK are likely to face significant water deficits by 2050, particularly the South East of England7.

“water should no longer be thought of as an infinite resource and the way water is managed and used needs careful consideration”

It is also expected that population levels will rise within the UK, reaching 70 million by mid-20298. This, coupled with the effects of climate change, is a significant threat to our way of life. Therefore, action is required now to dramatically change the way water is thought of in the UK. Water should no longer be thought of as an infinite resource and the way water is managed and used needs careful consideration. Therefore, accurate flow metering will be required in order to meet the future demands that will be placed on the supply of freshwater is that we manage water in a more sustainable way.

Non-Revenue Water

Leakage is not the only way water can be unaccounted for, it can often be better to use the term Non-Revenue Water (NRW) to describe the water that has been produced and is lost before it reaches the customer. The water can be lost in a number of ways: leakage or metering inaccuracies, unbilled consumption or even theft9.

It has been estimated that if the levels of NRW worldwide could be reduced by a third, this would provide water savings that would be sufficient to supply 800 million people and would offer a financial benefit of around USD 13 billion per year10. The global volume of NRW has been estimated to be 346 million m3 per day, equating to 126 billion m3 per year. If valued conservatively at USD 0.31 per m3, lost water can be valued at USD 39 billion per year10. 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 freshwater supplies in coming years.

The levels of NRW around the world vary significantly. For example, in Latin America and the Caribbean NRW is estimated to be 25.2 billion m3 annually whilst in Australia and New Zealand this drops to 0.3 billion m3, and in Europe approximately 9.8 billion m3 10. Australia and New Zealand have observed a significant reduction in NRW, attributable to the fact that there have been huge water loss reduction efforts over the last 10 – 15 years to better cope with longer drought conditions. This demonstrates the impact these efforts can realise.

With the demands being placed on freshwater supply, coupled with expanding populations the supply of freshwater to all is still a global challenge. The reduction of NRW can provide numerous benefits: reduced operating costs, better water resource efficiency and an increased water supply at a fraction of the costs associated with the building of new water production facilities.

In the UK, Ofwat11, the water industry economic regulator, has given the water companies a target of reducing leakage by 16% in the next five years. However, it is important to recognise when water leakage is actual leakage and not caused by inaccuracies in the flow meter measurements. The use of large diameter pipes in trunk mains shows that even though a very limited number of meters are of 1000mm diameter or larger, the flows that pass through these meters are vast, (i.e. 500 million l/d for 2 UK water companies). Therefore, any small inaccuracy in the flow meter measurements can result in vast volumes of water being incorrectly represented in the water balance.

Typically, these LDWFs do not tend to get removed from the ground for recalibration once they are installed. There are several reasons for this, including the inability of water companies to interrupt supply to its customers, together with limited facilities where such LDWFs could be calibrated. Therefore, the uncertainties associated with these LDWFs are generally unknown and thus have to be estimated.

For water companies to meet these leakage reduction targets, the accuracy of their meters must be determined. A better understanding of the uncertainties associated with the flow meter measurements allows them to be considered and accounted for in water balances. This results in the development of more accurate water balances and a more accurate reflection of water leakage rates. Providing more accurate flow meter readings will also allow the water companies to provide more accurate information into their models to be able to optimise their water network operations. Water abstraction limits With the exception of Scotland, mainland UK exhibits wide variation in water resources together with highly varied abilities to utilise those resources.

From discussions with one leading English Water plc12, it is clear that water company expectations are that by 2050 the legally enforced licensed abstraction volumes set by the Environment Agency (the environmental regulator) are set to fall to around 50% of those presently enjoyed; and that this generic reduction will be applicable nationally.

Most significantly, the Water Plc interviewed is planning to achieve this 50% reduction some 10 to 15 years earlier than the 2050 target i.e., soon after 2035. A remarkable ambition, which will require significant engagement from a wide variety of partners to deliver.
Verification evidence for both abstracted and water-into-supply volumes will likely therefore become critical performance indicators, requiring both non-invasive and non-intrusive on-site technical measurement, definition/assessment of meter traceability, rigorous analysis of all metering and metering system uncertainty components and the ability to dynamically calculate, in near real-time, the particular water company’s water balance.

Therefore, more accurate knowledge of large diameter flow meters will again be required in order to demonstrate that the water companies are meeting the regulatory demands. 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 Joint Industry Project (JIP) to investigate the meter uncertainties associated with large diameter water flow meters.

There is no official definition of what a large diameter meter is, but for this work any meters of 250 mm diameter or greater, will be considered to be large. Generally, these LDWFs are installed on distribution mains, transmission (trunk) mains and raw water mains carrying water abstracted from rivers to treatment works.

There is little or no independent assessment of the accuracy of LDWFs. These flow meters are disproportionately important when it comes to optimising distribution and calculating water balance and leakage.

The accuracy of these meters can be affected by several factors which occur upstream, in the vicinity or downstream of the meter. Ascertaining the potential influence of these factors is essential in order to improve accuracy and therefore understanding of the water distribution system. Developing a best practice approach to improve the accuracy of testing and assessment of LDWFs has the potential to place the UK at the forefront of optimising water distribution, globally.

The proposed JIP aims at filling knowledge gaps, updating existing guidance, and investigating 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 companies in their quest to meet the regulatory mandated leakage reduction targets. To summarise it helps to ensure more sustainable water management.