Estimation of Water Balance and Water Losses in Water Utilities – Experiences from the Belgrade Waterworks - page 6


In the first phase, the investigations included field surveys, inventory of all elements of the existing distribution network including legal and illegal water connections, water meters, manholes and water users. Water meter readings were checked 3 times during a three month period. Each pilot zone had one main input pipe that was used for flow rate and pressure measurement during a 6-month period.

An inventory of the existing connections and water meters was performed up to the maximal possible extent for each zone. Connections and water meters were checked and, in some cases, reconstruction was needed in order to provide technically appropriate connections. Investigations revealed significant discrepancies between the BWS technical requirements for distribution networks and connections, on one side and the situation in the field on the other side.

A significant portion of the secondary network (network downstream of the water meters) also does not fulfill the BWS technical requirements. This situation is further complicated by the fact that the majority of buildings in the considered zones were built without construction permits and were connected to the water supply distribution network through illegally constructed connections which generally do not meet technical requirements.

Pressures and flow rates were measured in the main input pipes on each of the four investigated areas during a 6-month period. A summary of the results, including measured minimal night flows are given in Table 3.


Table 3: Measured flows and pressures on the main supply pipes

Pilot zone

Night flow Qmin (l/s)

Qmin / Qaverage

Pressure (bar)

Kumodraž Selo

18 0.7



22 0.6



10 0.4


Velika Moštanica

12 0.6



The losses given in Table 4 were estimated by using measured results and water balance calculations for the considered time period.


Table 4: Estimation of water losses

Pilot zone

Water losses

% of delivered water


Kumodraž Selo

69 1,120


43 -


For the “Jajinci” and “Velika Moštanica” zones, the Unavoidable Average Real Losses (UARL) and Infrastructure Leakage Index (ILI) parameters were calculated (Table 5).


Table 5: Estimation of performance indicators

Pilot zone






Velika Moštanica