Theoretical and Conceptual Framework - Pattern Recognition for Reliability Assessment of Water Distribution Networks - page 29

standard features that could be helpful to assess the network reliability. A few possible add-
on's, in the order of complexity, could be:
-

Simulation run that models single failures of consecutive pipes and calculates the deficit
of pressure in the system.

- The similar simulation that calculates the demand reduction based on the adopted (quasi)

pressure-driven demand method.

-

Various optimisation modules that consider optimal design, operation and maintenance
measures from the perspective of the least cost that could also include reliability aspects,
such as the loss of revenue due to water shortage.

2.7 RESEARCH OBJECTIVES AND SCOPE

The general objective of the research presented in this manuscript has been to define a
reliability measure that is more tangible for day-to-day management and design/
renovation/expansion of water distribution networks, which could then be assessed i.e.
diagnosed having a user-friendly tool at disposal. Looking at the above list of the main gaps,
the specific research objectives have been dealing with the issues raised in the paragraphs
(A.3), (A.4), (B.2), (B.5), (C.1) and (C.4). The research has not tackled any aspect of failure
probability or mechanical reliability/availability and has been strictly focused to the network
hydraulic reliability. In that sense, using the term 'reliability' further in this manuscript,
actually relates to the network resilience.

2.7.1 Key Research Questions

In order to arrive at what has been defined as 'more tangible' reliability assessment, the
following research questions have been considered in this study:
1. What kind of network buffer can be best correlated to its reliability? Namely:
1.1. Is the available demand fraction (ADF) true descriptor of network reliability?
1.2. Are the demand-driven based reliability measures, sufficiently accurate?
2. What are the implications of the choice of particular network layout for the reliability?
Namely:
2.1. How the change in node connectivity affects the levels of service?
2.2. What is the effect of selected supply schemes, with or without balancing tanks in the
system?
3. To which extent can the monitoring of the basic hydraulic parameters help in predicting
the network reliability? Namely:
3.1. Do threshold values of flows and velocities for given layout exist, above which the
negative effect of the failure significantly increases?
3.2. What is the link between the pressure levels and the effects of potential failure in the
system?
3.3. Is there a link between the reliability and energy balance in the network?
4. How the reliability assessment affects the most economic design? Namely:
4.1. What are the differences between the most economic design and the most reliable
design?
4.2. Under what conditions is the increase of investment costs more affective for
improvement of the reliability than the increase of operation and maintenance costs?