Economic Aspects of Decision Making in Reliability Assessment of Water Distribution Networks - Pattern Recognition for Reliability Assessment of Water Distribution Networks - page 224

- Whilst NBI is pretty responsive towards the change of supply conditions, the values of I n
do not reflect them; they look pretty similar to those of network A . Next to the different
nature of NBI and I n , the contributing factor to the difference in results is the demand-
driven (DD) hydraulic calculation used to obtain I n , whilst the NBI is calculated by
pressure-driven demand (PDD) calculation. As a consequence, the curves created by the
DD calculation are seemingly more 'neat' but actually less accurate representation of the
network reliability.

8.9 ECONOMIC ASPECTS OF RELIABILITY ANALYSIS

Each of 630 scenarios (two supplying schemes in five different topographies, three altitude
ranges and 21 combinations of pipe diameters and pump speed) was further evaluated on four
different investment and operation cost options given in Table 8.5. The average costs of
investment and operation and maintenance (O&M) per topographic pattern and altitude range
are shown in Figures 8.22 and 8.23.

Investment O&M

1,600,000

1,400,000

1,200,000

1,000,000

800,000

600,000

400,000

200,000

-

Figure 8.22 Average annual costs (US$) of investment and O&M of all A-scenarios

Investment O&M

1,600,000

1,400,000

1,200,000

1,000,000

800,000

600,000

400,000

200,000

-

Figure 8.23 Average annual costs (US$) of investment and O&M of all B-scenarios