Estimation of Water Balance and Water Losses in Water Utilities – Experiences from the Belgrade Waterworks - page 7

 

For the “Jajinci” zone further analyses were performed and performance indicators were estimated by water balance calculations over a 180-day period, for which measured results were available (Table 6). According to IWA suggestions, the following parameters were obtained for the Jajinci region:

  • Total number of connections in the network: 1,246
  • Position of water meters in the network: 5-10 m, average 7.0 m from regulation line;
  • Total length of the water distribution network: 17.179 km
  • Average pressure during regular operation: 63.0 m
  • Density of water connections: 72.5 per km

 

Table 6: Consumption and water losses in the “Jajinci” pilot zone

Category

No. of water meters

Average daily consumption (m3/day)

Total consumption within balance period (m3)

% of total losses

% of input

Per water meter

In zone

Per water meter

In zone

Water losses

1600.5

288,090

100

52.93

Estimated consumption due to water meter malfunction (measured discharge was zero)

145

1.46

211.7

262.8

38,106

13.23

7.00

Estimated consumption that was not measured

46

1.46

67.2

262.8

12,089

4.20

2.22

Estimated unauthorized consumption

520

1.46

759.2

262.8

136,656

47.44

25.11

Total apparent losses

1038.1

186,851

64.86

34.33

Real losses

562.4

101,239

35.14

18.60

 

Discussion

Although all the investigated areas were made up of predominantly residential properties without any industrial water users, measured results show significant night flows, indicating potentially high levels of water losses. Further field investigations are needed (e.g. minimal night flow method) in order to more accurately estimate levels of water losses.

Investigation results also revealed that pressure in distribution network in three out of four investigated pilot zones (Kumodraž Selo, Jajinci and Baćevac) were rather low, and therefore pressure management is not viable method for water losses reduction.

The CARL indicator for the Jajinci region water network is calculated as follows:

  • Real losses during analyzed period (180 days during 2004.) : 101,239 m3
  • CARL: 481.1 l/conn.day

The UARL for the Jajinci region is 67.30 l/day per connection. For this region, the indicator ILI is estimated at the level of 7.15, indicating significant water losses in the area. It is worth mentioning that extensive water losses from water meters were discovered (Babic et al. 2005). In addition, water users are not interested in repairing water meters due to the low unit price of water, which stimulates irrationally high water consumption.

Conclusions

The Belgrade Water Company obtained significant results from the presented investigations in four pilot zones, which contribute to the definition of the common procedures and minimum extent of information necessary to implement a strategy for the reduction of water losses in the whole Belgrade Waterworks. The outcome of the investigations in all pilot zones is that reliable measurements are essential for the reliable estimate of water losses. It is also necessary to regularly check the global water balance in parts of the network and to continuously measure the night flows, as the best short-term indicator of the water losses in the network.

In all investigated areas significant water losses exist but further investigations are needed to estimate water losses components and to assess reliability of estimated data. In calculating the UARL indicator, only average pressure was considered, although pressure variations may be significant in some areas. In considered suburban regions, the length of connections between the water meters and the water users were very large, which additionally contribute to increase of water losses.