Water monitoring
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.
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 equating to 126 billion m3
per day, conservatively at $0.31 per m3
per year. If valued , lost water can
be valued at $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. In recent years, the UK Water Industry has made great strides in leakage reduction. However, with the Ofwat requirements for a 16 per cent reduction in leakage by 2025 much more work is required.
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.
Instrumentation Monthly November 2022
ABSTRACTION LIMITS From discussions with one leading English Water 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 per cent of those presently enjoyed. Most significantly, the Water plc interviewed is planning to achieve this 50 per cent 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. 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 which is a totally unsustainable situation. Therefore, knowledge is required about the amounts of water being abstracted 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 therefore become critical performance indicators. This will require both non-invasive and non-intrusive on-site
FLOW MEASUREMENT It is important to understand how flow meters work. A significant proportion of modern flow meters rely on assumptions about the flow profile of the fluid within the pipe, i.e. assuming a fully formed symmetrical flow profile. Bends, valves, and other pipe components upstream of the measurement device will affect the assumed flow profile and therefore the accuracy of the meter. Uncertainty is the degree of doubt about a measurement. Undertaking an analysis of the uncertainty involves identifying the main influences that affect the final measurement. This will result in a number which represents the “margin of error” in the measurement. Applying this across the network gives an uncertainty in the water balance; that is, a margin of error within which the mass balance should lie. Identifying the main contributors to this figure can ensure that capital expenditure is targeted to areas in the network where it will produce the most benefit. With flow monitoring becoming an increasingly important part of a water company’s business, it is therefore crucial that:
Good measurement practice is always followed
Established procedures and processes are used and regularly updated
Staff training and competence is recorded and regularly verified
This helps to ensure that the data obtained from the metering network is reliable, can be used in demand forecasting, and strategic planning. This data also acts as inputs to a range of numerical analysis techniques, such as gross error detection, uncertainty analysis and data reconciliation. These techniques are cost- effective methods of improving the effectiveness of network monitoring and are now being frequently applied in the water industry. TÜV SÜD National Engineering Laboratory is
currently developing a wide-ranging Joint Industry Project (JIP) to investigate the uncertainties associated with large diameter water flow meters. The core objective of the project is to is to improve the optimisation of water management. A better understanding of the flow of water into the distribution network will lead to more accurate water balances and leakage determination. It will also support the water companies in their quest to meet the regulatory mandated leakage reduction targets and ensure more sustainable water management.
TÜV SÜD National Engineering Laboratory
www.tuvsud.com/en-gb/nel
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