Impacts of Node Connectivity on Reliability of Water Distribution Networks - Pattern Recognition for Reliability Assessment of Water Distribution Networks - page 171

on statistically small sample of networks and possibly insufficiently different in the level
of connectivity, it is believed that this conclusion would not change in case of larger and
more diverse sets of networks.
2. The approach based on graph theory has shown more consistent results. It is however that
more simple measures such as GD and Deg avg , correlate better than the more complicated
ones. It is yet to be investigated if the elements of graph theory can sufficiently be
integrated into the hydraulic aspects of water distribution networks, for instance by using
weighted graphs to reflect pipe flows or resistances. The difference between undirected
and directed graphs, the latter coinciding with flow directions in the pipes, analysed in
this research has been insignificant. This is the reason why all the NodeXL results have
been presented for undirected graphs.
3. The NDT connectivity measures show less consistency than the NodeXL results. They
appear to be rather coarse and reflect the difference in connectivity only in case of visibly
different network layouts. It is here as well that simpler NGI and NCF avg correlate often
better than more complex NCIx and NSIx . Also, having the most of these values in the
range between 0 and 1, regardless the number of nodes/links, gives impression that these
factors/indices would work better as parameters of more complex formula including the
network resistance and supplying heads. Having lower value of connectivity index for
much larger network can be confusing at a time.
4. The preference shown for the Spearman test compared to the Pearson test would need to
be verified on a larger sample of data sets i.e. evaluated networks. Nevertheless, the
preliminary results obtained by the Pearson test show that the degree of correlation would
not lead to different conclusions in case this test was used for more complete statistical
analysis instead of the Spearman test.
5. Although used mostly for social networks, NodeXL has proven to be pretty convenient
although lacking direct link with EPANET software. The range of features enabling good
visual presentation of graphs gives impression that this MS Excel template can be used
for more water distribution analysis, for instance for network zoning, district metering
areas, etc.