Water monitoring


The water flow meter knowledge gap


By Carl Wordsworth, head of Water Sector at TÜV SÜD National Engineering Laboratory


W


ith the growing impacts of climate change being felt across the world, 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 by 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 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 per cent over the next five years throughout the UK, water companies are undertaking 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


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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 per cent 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 per cent of our planet, however only three per cent 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


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 per cent of its freshwater needs by 2030. Coupled with the expected rise in the global population, estimated to be at 8.3 billion by 2030, this will result in massive challenges for the worldwide supply of fresh water. Currently, the estimated daily personal water consumption rate in the UK is on average 152 l/day (as per 2021), equating to an estimated total daily usage of 14 billion litres per day. Worldwide, climate change will have a significant impact on the volume of useable freshwater, and by 2025 it has been estimated that two-thirds of the world’s population may face water shortages. 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.


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.


November 2022 Instrumentation Monthly


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