Pressure Management of Water Distribution Systems

Understanding and Predicting the Benefits

Portuguese Utilities Workshop, September 2015

A series of significant developments in practical concepts for understanding, analysis and prediction of the many benefits of pressure management have been actively promoted by IWA Water Loss Specialist Group members over the last 12 years. These concepts are now being successfully implemented in many countries, to help Utilities to reduce leakage and improve asset management performance. Seven Portuguese Utilities within the AGS and Aquapor groups of Companies attended a Workshop organized by Aguas de Cascais on 23rd and 24th September, to improve their understanding of how to use these concepts for effective targeting of further pressure management appropriate to their own distribution systems.                                                          

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The 2-day Workshop was presented by Allan Lambert of Water Loss Research & Analysis Ltd, and attended by 18 personnel from Aguas de Cascais, AGS, Aguas de Alenquer, Aguas de Figuera, Aguas de Gondomar, Aguas do Sado, Aquapor and Lusagua.  The presence of 7 Utilities with diverse characteristics was helpful in showing how the application of the IWA practical concepts using Utility-specific data can help to explain differences in calculations, assumptions, NRW and leakage management performance, achievable targets and opportunities for pressure management between different Utilities. The conclusion of the recent EU Reference Document Good Practices on Leakage Management, that there is not a ‘One Size Fits All’ solution, were clearly supported by these interactions.

After an overview of the IWA Practical Approach to managing Leakage, four of the Utilities completed a water balance and PIs calculation using the EurWB&PICalcs free software. The results and aspects of data accuracy in such calculations were discussed, and two additional methods of checking annual leakage – component analysis and night flow analysis – were explained. Delegates then practiced using AZP&NDFCalcs free software to systematically calculate zonal average pressures and Night-Day Factors (which relate night leakage rate in m3/hour to daily leakage rate). These figures could then be weighted to systematically calculate current approximate estimates (40 to 45 metres) of average Utility system pressure, to improve calculations of Unavoidable Annual Real Losses and Unavoidable Background Leakage.

Repair frequencies were found to be relatively high (20 to 58 per 100 km/year on mains; 6 to 16 per 1000 services/year), but ILIs close to 1.0 were achieved in two of the Utilities by   numerous relatively small DMAs and remarkably rapid repairs and low leak run times.

The concepts underlying relationships between pressure and leak flow rate (FAVAD N1), pressure and burst frequency (N2), pressure and extension of infrastructure life, and pressure and consumption (N3) were then explained, first in broad terms, then in more detail. There seems little doubt that the Utilities will now be able to target specific parts of their systems for further pressure management in which the costs and the benefits can be predicted.

Participants feedback

Pedro Perdigão, Director-General, Aguas de Cascais: Since we´re just starting to implement a more comprehensive pressure management programme, as a fourth vector of our water losses reduction strategy, having an intensive and thorough discussion, of leakage and pressure optimization, with someone with an experience as long and as vast as Allan´s, was very fruitful. With a systematic approach to the questions involved, besides sharing concepts, Allan focused on demonstrating, with several very different case studies and applications, the equations and techniques already available in this relatively young science of water loss management. It was a very inspiring workshop.

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