Diagnostics of Regular Performance of Water Distribution Networks and its Relation to the Network Reliability - Pattern Recognition for Reliability Assessment of Water Distribution Networks - page 181

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0.9

0.8

PBI50
PBI151
PBI200
NPI50
NPI151
NPI200
NRT50(w)
NRT151(w)
NRT200(w)

0.7

0.6

0.5

0.4

0.3

0.2

0.1

0

0.92 0.93 0.94 0.95 0.96 0.97 0.98 0.99 1

ADFavg

Figure 7.6 Reliability measures for networks ngt 01-50, 01-151 and 01-200 for demand growth of 32%

Figure 7.4 shows two networks with GA optimised pipe diameters supplying the same total
demand. Again, the network O20sn80 is more reliable but in this case has rather similar
buffer compared to O20sn73 . Although optimised for lower total demand, the network
O20sn73 is less reliable than sn73 , as well as is the case with O20sn80 and sn80 , which can
be seen by comparing the results in Figures 7.3 and 7.4.

Figure 7.5 shows also that the better connected networks, sn0199 and sn0109 , are more
reliable than sn0179 . These two perform within similar ADF avg range despite the fact that
sn0199 supplies more than twice the demand of sn0109 . This is possible as this network is
the only of the three that is connected with two pipes to the source. Nonetheless, the higher
demand results in the lower PBI and NRT values, also compared to sn0179 .

Although kept with fixed diameters of 100 mm only, the geometry of the networks ngt 01-50 ,
01-151 and 01-200 , shows more realistic values of NRT , in the range of 9 to 37 hours. In
Figure 7.6, these values have been expressed in weeks, to maintain the same scale of the Y-
axis as in the previous three diagrams. Like in the case of three sn01 networks, the better
connected networks, ngt01-151 and ngt01-200 , are more reliable than ngt01-50 . Equally,
these two networks have the similar ADF avg range because the bigger one, ngt01-200 , also
supplies the higher demand than ngt01-151 . Consequently, the smaller network has a bit
more buffer expressed in the difference between the values for NPI and NRT . The higher NPI
value of ngt01-50 compared to the other two is due to lower nodal elevations.

The similar trend can be observed analysing the PBI values. The two bigger networks show
similar values and more favourable range of ADG avg than the smallest one. The difference in
the PBI values is however much smaller than in case of NPI and NRT , likely resulting from
central positions of the source i.e. the lower level of friction losses. Last but not the least, the
generally higher values of ADG avg observed in case of the three ngt networks are also caused
by good connectivity of the source. Hence, the preliminary analysis of all the figures
confirms the correlations that can be summarised in the following bullets:
- Demand increase of a network causes higher friction losses (i.e. the lower nodal
pressures/demands) leading to lower values of ADF avg , PBI , NPI and NRT .
- At the same level of demand, better connected networks will have more favourable range
of ADF avg .