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GIS as the tool

As already mentioned, it was decided to use GIS as the foundation for the development of the tool. As part of the GVD project a common GIS based asset management system has been established.

The technology used is:

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  Microsoft SQL
  
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  ESRI ArcGIS
  
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  Miner & Miner ArcFM
  
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  Safe Software FME
  

Multi criteria selection:
In the tool a kind of multi criteria selection is used. Multi criteria selection is not a new invention, neither in general nor in this particular field. The Care-W project running under the fifth framework program of the European Commission caused a thorough discussion around the multi criteria techniques (Le Gauffre, Laffréchine et al, 2002) and a survey of multi criteria techniques for use in water distribution network rehabilitation (Le Gauffre, Bauer et al, 2002).
The Care-W project takes into account a long range of criteria, as for instance: rehabilitation costs, coordination, disturbances induced by rehabilitation, water quality, water loss, water supply interruptions and more. As an important objective for our project was to maintain focus on feasibility, our software tool is less ambitious and is therefore more limited in the number of included criteria.
The selection criteria used, are classified in two groups. One group is containing criteria that define the probability for failure on water mains or fittings, and a second describing the consequence of a failure.
For each of the criteria in the two groups and for all the water mains in the distribution network, a score value between 1 and 6 is applied. Each of the parameters is then multiplied with a weight factor, and the result is used to calculate two values, The Probability Score (PS) and the Consequence Score (CS). The Probability Score and the Consequence Score thus multiplied with a weight factors and the result are used to calculate the final Rehabilitation Factor (RhF). As can be seen, this method resembles how risk evaluations often are calculated:
Risk = Probability * Consequence