 |
| Simple method of forecasting % reduction in new bursts from % reduction in maximum AZP pressure |
Reducing the maximum Average Zone Pressure (AZP) in a DMA can have a very significant effect on the level of new bursts. In many cases, a reduction in maximum AZP of a given percentage results in a higher percentage drop in the level of new bursts.
Members of the Water Loss Task Force (1) recently reported data from 112 pressure management schemes around the world. They found that the average pressure reduction across all the schemes was 37%, resulting in a reduction in new bursts of 53%.
The above graph shows a simple overview of the Water Loss Task Force data. The average line shows that the % reduction in new burst frequency is 1.4 times the % reduction in maximum AZP but there is a wide scatter; the lower line is 0.7 times and the upper line is 2.8 times the % reduction in maximum AZP.
 |
Reduction (%) in new burst frequency influenced by initial burst frequency
|
An improved prediction concept currently being tested by the Water Loss Task Force members uses the concept that if there is already a high burst frequency before pressure management (see red point in graph above) then a small reduction in the maximum pressure will produce a significant reduction in new burst frequency (move towards blue point). However, if there is already a relatively low burst frequency before pressure management (blue point), then any reduction in pressure (from blue to green point) would have a lesser effect on new burst frequency. However, it will still create a greater factor of safety and extend the working life of the infrastructure.
References
1) Thornton J and Lambert A. "Pressure management extends infrastructure life and reduces unnecessary energy costs." Proceedings of IWA Special Conference 'WaterLoss 2007', Bucharest, September 2007.