Managing NRW – Roof Storage Tanks & Intermittent Supply


Masterclass for Aguas de Saltillo with

international experts

Nov 2016, Llandudno

Some of the concepts and practical approaches now available for managing NRW become more difficult to apply when water is delivered to consumers through large roof storage tanks, rather than by direct pressure. Where supply is also intermittent, the problems of quantifying and reducing NRW are then compounded by excessive frequencies of leaks and bursts, damage to the distribution system and impairment of meters, and reduction of asset life. The recommended solution is to move to a 24/7 policy of continuous supply, but this is easier said than done. However, some Utility systems (Malta), and Malta and Cyprus case studies in with roof storage tanks have achieved continuous supply with ILIs close to, or even below, 2.0

Aguas de Saltillo is a regional capital city in Mexico at 1600m elevation with a semi-arid climate, historically over-exploited deep aquifers and high Non Revenue Water. Since 2001, when Aguas de Saltillo started its operations, the system has moved from customers being supplied 10% of the time to around 70%, but frequencies of new bursts for mains, and new leaks on services, remain extremely high. The Company is implementing a 3-year program of pressure management and district metered areas. After accessing information on the LEAKSSuite website, including the EU Reference document on Good Practices (2015), the Utility recognised the importance of formulating an appropriate sequence of actions, and sought a better understanding of how to identify this sequence for their system, how to interpret the night flow measurements, and how to predict the resulting benefits and rate of progress.

Recognising that this is a common problem in many international systems with roof storage tanks, ILMSS Ltd contacted several international IWA colleagues with particular expertise in dealing with this particular problem, to assist Aguas de Saltillo in trying to achieve their objective. The response was exceptional. Bambos Charalambous (Cyprus), Fabio Garzon (Colombia), Marco Fantozzi (Italy), Michel Vermersch (Brazil and France), and Mohammed Alshafey (Jordan) all agreed to attend a low budget Masterclass in UK hosted by ILMSS Ltd, on a pro-bono basis at their own expense, to exchange knowledge and experiences on this specific topic with Nicolas Monterde and Juan Bravo from Aguas de Saltillo, and others with interest in this topic. Several other invited international specialists – for example Julian Thornton and Alan Wyatt, with experience in Mexico – were unable to attend only because of prior commitments.

Others participating in the Masterclass, moderated by Allan Lambert, were Ignacio Pena and Tory Wagoner from LEAKSSuite sponsors (JOAT, South Africa and Cavanaugh, U.S.A); Luke Pace (Malta WSC), and two lecturers (Dr Guangto Fu and Dr Raziyeh Farmani) and two postgraduate students (Harry Liu and David Forber) from the University of Exeter, Centre for Water Systems, and David Pearson.

Day 1 discussion commenced with a detailed presentation by Aguas de Saltillo, followed by a review of basic concepts to ensure all delegates were familiar with latest developments in Assessing NRW and its components from Water Balance, Night Flows and Component Analysis, and Assessment of Uncertainty and Data Validation.

Day 2 commenced with each of the international visitors introducing themselves and outlining their experiences and personal perspectives on key issues and problems associated with NRW assessment and management on systems with roof tanks, with and without intermittent supply. This was followed by feedback from the Exeter University Group.

The afternoon continued with a presentation on ‘How excess pressure influences leak flow rates, burst frequency and asset life’ (Allan) followed by discussion sessions on:

  • Taking Back Control’ for Intermittent Supply (lead by Bambos).
  • Assessing NRW and its Components using Water Balance (lead by Allan and Tory)
  • Using Night Flows (lead by Luke and Marco)

Day 3 consisted of further detailed discussion sessions with multiple contributions on:

  • Multiple contributions on Unbilled Authorised Consumption, Unauthorised Consumption, Apparent/Commercial Losses and even examples of unauthorised billed consumption (lead by Bambos and Michel);
  • Customer Meter Selection/Installation/Testing/Replacement Strategy
  • Adverse influences of incorrect customer meter installation and intermittent supply
  • Use of Unmeasured Flow Recorders (UFRs) and On/Off valves in storage tanks
  • Experiences and Opportunities with Smart Metering

On the morning of Day 4, Bambos made a presentation on practical aspects of effective leak detection, followed by a more general discussion on leakage detection and economic intervention. This was followed by a discussion session on current philosophy for the sequence of creating DMAs and PMAs, in which it was concluded that, with recent knowledge of predicting burst reduction and international experiences, it was generally preferable that pressure management zones should precede creation of DMA (flow only) sub-zones, to seek to reduce burst frequency and calm the network. The absolute importance of creating Average Zone Points for each PMA and DMA, to enable reliable analysis and predictions, was emphasised.

On the afternoon of Day 4, the discussions focussed on how the experiences shared and developed in the Masterclass could assist Aguas de Saltillo to improve their strategy for increasing the number of Zones with continuous supply, including how to prioritise selection of Zones for pressure management in the 250 zones which were planned. Several new practical ‘twists’ on selection and interpretation of night flows in intermittent supply zones were identified, together with a suggestion from Mohammed as to why the N2 exponent for pressure-dependent bursts might be expected to approximate to a cubic relationship.

The Masterclass identified the need for readily accessible presentations and papers on how best to move from intermittent to continuous supply in Zones where customers are supplied through storage tanks. To seek to remedy this, ILMSS Ltd will set up a new Info-Hub on this topic on the LEAKSSuite website, and the international specialists volunteered to provide copies of their best non-copyrighted papers and presentations on this topic in recent years for free access to anyone who may benefit from them. There will be more on this topic in the end-of year Blog on website statistics and future initiatives for 2017.

Acknowledgements and Thanks. Firstly, to the international specialists who gave freely of their knowledge, time and travel to UK at their own expense to attend the Masterclass, to further international understanding on this and associated topics. Their philanthropy follows the best traditions of the IWA Water Loss Task Force, now the Water Loss Specialist Group. To Aguas de Saltillo and other Sponsors for their continued support of the LEAKSSuite website, to Cavanaugh for sponsoring the Course dinner; and to all those who attended the Masterclass. Their feedback is shown below.

Participants feedback:

Mohammad Alshafey, Head of Research and Planning, Aqaba Water

  • Any water utility or water professional would be extremely lucky to be part of one of Allan Lambert’s masterclasses. I have never been through anything as powerful and insightful during my time in the water sector. Allan and the participating experts are of high calibre and combine theoretical and practical experience in water loss reduction. I would highly recommend the masterclass to all water leaders and professionals.

Ing. Nicolas Monterde Roca, Gerente Tecnico, Aguas de Saltillo SA de CV, Mexico

  • Thank you so much for your help and for this wonderful week!

Bambos Charalambous, Hydrocontrol Ltd, Cyprus

  • It was indeed such a pleasure meeting again old friends and colleagues and spending time together discussing and exchanging knowledge and experiences on such an interesting topic. Many thanks for organising this.

Dr Marco Fantozzi, Studio Marco Fantozzi, Italy

  • Thanks for offering me this opportunity. It was great to exchange knowledge and experiences on NRW management with great experts and old friends. Master classes like this should be run on a regular basis.

Michel Vermersch, MF&E, Engenhieros Associados: Salvador, Brazil and Paris, France

  • The master class was a great experience, and also the opportunity of meeting old friends and colleagues.

Tory Wagoner, Cavanaugh Solutions, U.S.A.

  • The concept of a Master Class with a combination of industry experts and a water utility worked exceptionally well.  I was amazed by the level of technical experience and education that was available at the session.  The class was well worth the investment of time and resources expended.

Ignacio Pena, Joat Consulting, South Africa

  • Regards and thanks for everything, this was amazing.

David Pearson, David Pearson Consulting, UK

  • Good to be able to share and discuss issues with other people from around the world, even during the limited time I was able to attend.

Luke Pace, Engineer | Meter Section | Water Services Corporation | Triq Ħal Qormi, Ħal Luqa

  • Thank you for your hospitality and brilliant organisation for this masterclass!

Harry Liu, Post-Graduate Student, University of Exeter Centre for Water Systems

  • Thank you for organising and inviting me to the workshop, it has immensely helped my understanding in the theoretical as well as the practical side of urban water distribution; I also found intermittent water supply to be very interesting.

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