Page 156 - Water Loss Control

134 Cha pte r T e n

Component of Background Reported Unreported
Infrastructure (undetectable) Losses Breaks Breaks
Mains Length Number/year Number/year
Pressure Pressure Pressure
Min loss rate/km* Average flow rate* Average flow rate*
Average duration Average duration
Service Leakage through Reported overflows: Unreported overflows:
Reservoirs Structure Flow rates, duration Flow rates, duration
Service Number Number/year Number/year
connections, Pressure Pressure Pressure
main to edge of Min loss rate/conn* Average flow rate* Average flow rate*
street
Average duration Average duration
Service Length Number/year Number/year
Connections Pressure Pressure Pressure
after edge of Min loss rate/km* Average flow rate* Average flow rate*
street
Average duration Average duration

* At some standard pressure.
Source: Water Loss Control Manual, 1st ed.

TABLE 10.6 Parameters Required for Calculation of Components of Annual Real Losses

The BABE annual component analysis model was first calibrated and successfully
tested using British data in 1993. It was rapidly extended to cover economic analysis to
assess the economic frequency of active leakage control interventions, and since then
has been used in many countries.
The BABE annual model can be considered as a statistical model, in that it does not
seek to identify every individual leakage event and calculate an annual loss volume;
rather, it groups together similar events, and does simplified calculations. The larger
the number of events, the better the accuracy of the calculated values, so BABE annual
models work more reliably with large systems. The BABE model used for calculation of
unavoidable annual real losses (UARL) is limited to systems with more than 3000 ser-
vice connections (based on detailed sensitivity analysis this value was revised down
from 5000 connections in 2005).
The powerful combination of BABE and FAVAD concepts meant that, in the late
1990s, a range of simple spreadsheet models could be developed to approach a number
of leakage management problems for individual systems, on a rational and systematic
basis. Figure 10.1 shows the range of problems which has been successfully modeled.
BABE modeling or component analysis can also be undertaken at district or zone
level breaking down night flows into the key consumption and real loss components.

10.5 Using BABE Modeling Concepts to Prioritize Activities
It is not recommended that component analysis is undertaken on its own to derive a
volume of annual real losses because there is likely to be a significant level of uncertainty