Environmental Engineering Reference
In-Depth Information
CHAPTER 8
in Reliability Assessment
of Water Distribution Networks
1
The research presented in this chapter compares implications of increased investment and
operational costs for the reliability of networks with direct pumping and those combined with
balancing storage. Economic aspects have been taken into consideration by applying the
Present Worth method. Using this approach, the reliability of two simple network layouts has
been analysed manipulated through five different topographical patterns, three altitude ranges
and four economic scenarios. Each of the 120 scenarios was further tested on 20 additional
designs comprising gradual increase of pipe capacity combined with reduction in pumping
capacity, while targeting the similar minimum pressure. The network reliability has been
assessed with the resilience indices introduced in Chapter 5, namely the
NBI
and
I
n
. To
process efficiently total 2520 scenarios, the network diagnostics tool (NDT) used in the
analyses in Chapters 6 and 7 has been upgraded with cost calculations. The results show that
cheapest design scenarios are not necessarily the least reliable ones. Furthermore, better
reliability for the same level of investment is achieved if done into additional pipe capacity
rather than into pump capacity/operation. Moreover, both strategies confirm that the point
after which the further investment is useless indeed depends on the choice of economic
parameters.
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