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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 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 using larger meters that we quantify how much water is being abstracted from underground aquifers, rivers and other water bodies to provide 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 through calibration on a traceable flow rig, there has been 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.
“the need for accurate measurement on large diameter transmission (trunk) mains is of national importance”
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 and global population increase.
With UK regulators requiring leakage reduction of 16% over the next five years, throughout the UK, water companies are undertaking more and more transmission (trunk) main balances to locate bursts, leakage or unaccounted for water (UFW). Large diameter metering is a key element for obtaining accurate and auditable results but can be expensive. Therefore, 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 500 mm or greater. This equates to daily flows in the region of 500 million litres per day per company. To allow the water companies to provide accurate water balances and to reduce UFW 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 consumption demands
Worldwide, climate change is going to have a significant impact on the volume of useable freshwater that is available to a rapidly expanding population. Water covers 70% of our planet, however only 3% of this water is freshwater and of this, two-thirds is either frozen or unavailable for use. 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 rate of water consumption 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. In the U.S, within as little as 50 years large regions of the country are expected to see freshwater supplies reduced by as much as a third, with the possibility of 83 out of the 204 water basins experiencing shortages by as soon as 2021.
“at the current rate of water consumption, by 2025 it has been estimated that two-thirds of the world’s population may face water shortages”
With the 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 2030. Coupled with the expected rise in the global population, currently estimated to be at 8.3 billion by 2030, this will result in massive challenges for the worldwide supply of fresh water.
In the U.S. on average the daily personal consumption rate is between 80 – 100 gallons, equating to an estimated total daily usage of 345 billion gallons. By 2100 it is estimated that the U.S. population will rise to over 500 million people, therefore increasing the amount of water stress across the country.
Currently agriculture is the largest user of freshwater, with 70% going to this area. With food production expected to grow by 60% by 2050, the demands on freshwater supply are going to be increased. It has also been estimated that the freshwater needs of manufacturing are likely to increase by 400% by 2050, placing further demands on water supplies.
To meet the expected demand on freshwater, action is required now. It will be necessary to reduce demand and increase supply to meet future freshwater requirements. 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.
Potential ways this can be undertaken include:
• Applying circular economy principles to the water sector
• UFW reduction, i.e., leakage reduction
• Reduction of personal water consumption
• Increase the use of water transfers between areas of high supply and high-demand
• Building new reservoirs
• Building new desalination plants
Water regulation – leakage reduction
Currently there is no national standard within the US to address water loss. However, the American Water Works Association (AWWA) has developed the M36 -water loss control program. M36 includes auditing software that can be used by the water 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, coupled with the development of the Senate Bill 555 in California, which enables the State Water Control Board to place performance standards on water suppliers regarding water loss, could show a move toward a more performance-based structure for U.S. water utilities.
The lack of a national standard in the U.S. can be compared to the United Kingdom, where the water regulator Ofwat, has recently set stringent targets on leakage reduction for all of the UK Water Utilities. In the next five years Ofwat expects the water utilities to have reduced overall leakage by 16%.
Losing 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. i.e. NRW = Unaccounted for Water + all other water that is used but not charged for. The water can be lost in several ways: leakage or metering inaccuracies, unbilled consumption or even theft.
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 year. 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 year. 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 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. However, it is important to recognise when water leakage is actual leakage and not caused by inaccuracies in the flow meter measurements.
“a better understanding of the uncertainties associated with the flow meter measurements allows them to be considered and accounted for in water balances”
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.
Abstraction limits
With the exception of Scotland, mainland Britain exhibits a wide variation in water resources together with highly varied abilities to utilise those resources.
From discussions with one leading English Water plc, 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.
“verification evidence for both abstracted and water-into-supply volumes will likely become critical performance indicators”
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.
Groundwater is the most important source of freshwater, as around the world more than two-billion people are supplied with freshwater from 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. The water quality is also affected, with seawater intrusion into the aquifers resulting in large concentrations of undesirable minerals, a situation which is totally unsustainable. Therefore, knowledge about the amounts of water being abstracted are required to manage the levels of water within the environment. Accurate knowledge requires accurate flow metering.
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, a water company’s water balance. To undertake this, more accurate knowledge of large diameter flow meters will again be required.
Industry action
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 uncertainties associated with large diameter water flow meters.
There is little or no independent assessment of the accuracy of LDWFs, yet 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 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 data generated from this proposal will represent an unrivalled piece of work looking at how the uncertainties of large diameter water flow meters are affected by pipe size, flow disturbance, placement, age and fluid velocity.
The core objective of the project is to is to improve the optimisation 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
The JIP aims to fill knowledge gaps, update existing 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 companies in their quest to meet the regulatory mandated leakage reduction targets and ensure more sustainable water management.
