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12% of the annual budget. The significant component is the depreciation of assets that
contributes 39% to the total cost.
Materials
Energy/fuel
Other operational
Salaries
Depreciaton
Financial and other
Maintenance
Figure 8.2 Total cost structure of BWS (Cvjetković, 2008)
The proportion of the costs as in Figure 8.2 may look different in different systems. Water
supply in developing countries is normally run by relatively large number of staff and cheap
labour, while developed countries will strive to higher level of automation due to much
higher costs of labour. Furthermore, next to topographical conditions, the energy input may
also be influenced by strategic choices driven by the costs and reliability of electricity supply.
For instance, one implication of erratic electricity supply could be to build additional
emergency storage volume in the network. Finally, the depreciation is based on the proper
estimates of the technical and economic lifetime for the selected level of maintenance, but
also depends on the conditions agreed for repayment of loans used for construction; here
again, the distribution network will utilise the most of annuities. The technical lifetime of the
network components can vary significantly as shown in Table 8.1 (Trifunović, 2006), and in
well maintained networks it can be extended even further. Hence, the choice amongst
particular technical solutions that will improve network reliability has to take into
consideration all these aspects before being made.
Table 8.1 Technical lifetime of distribution system components (Trifunović, 2006)
Component
Period (years)
Transmission mains
Distribution mains
Reservoirs
Pumping station - facilities
Pumping station - equipment
30 - 60
30 - 80
20 - 80
20 - 80
15 - 40
8.2
PLANNING OF COSTS IN WATER DISTRIBUTION
Investment costs of water distribution networks are estimated during the design process by
applying the following simplified approach (Trifunović, 2006):
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