# GIS-Based Identification of Locations in Water Distribution Networks Vulnerable to Leakage
## 3 Materials and Methods
### Parameters Used in Vulnerability Analysis of the WDN  
The selection of the parameters (leakage conditioning factors) in this study was restricted due to the limited available data provided by SEWA. The parameters used in this study were divided into operational and fixed physical parameters. The method considers three fixed physical factors that do not change with time, such as pipe length per junction, the number of fittings per length and pipe friction factor, and three varying operational factors (drop in pressure, drop in flow and drop in chlorine). Operational parameters refer to the hydraulic and water quality components in the WDN that vary and fluctuate with time. * Drop in pressure: Pressure in the pipelines affects the performance of WDNs, as it increases leaks and the corresponding water losses. In addition, there is a direct relationship between drops in pressure and leakages in WDNs [36]. Pressure fluctuations also affect the performance of WDNs due to trapped air, pressure regulating valve issues, old or clogged pipes, or high usage in one line. A study by [37; 38] connects pressure changes and leakages by evaluating various leak types in pipe materials. Pressure surges also impact the performance of WDNs due to flow velocity changes caused by multiple factors, such as entrapped air, the start or stoppage of pumps, or quick valve opening and closing. According to a study by [39], pressure surges directly contribute to leakages in WDNs--significantly so when the water pipe walls are damaged. Therefore, pressure drops, fluctuations, and surges are significant signs of leakages. * Drop in flow: Flow in the WDN is another operational parameter directly related to leakage. Flow drops and leakages are interrelated and can both have negative impacts on the performance of WDN. If there is a significant leak in the system, it can reduce the pressure and flow rate downstream of the leak. This can result in a loss of performance or efficiency in the system, as well as potential safety hazards. Flow is usually used to assess the amount of leakage using the mass balance [40]. * Drops in chlorine were considered an indicator for reducing water quality in the WDN. When there is a significant water leak, it can cause a drop in water pressure in the system, which may allow outside contaminants to enter the water pipes. If the contaminants are microorganisms, the chlorine in the water may react with them, which can cause the chlorine levels in the water to decrease. Therefore, a decrease in chlorine levels in the water can be an indicator of a water leakage, as it suggests that the chlorine is reacting with contaminants that have entered the water supply through the leak. Water utilities monitor chlorine levels in the water to identify any changes that may indicate a potential water leakage or contamination issue. The pressure (in bar) and flow data (in m\({}^{3}\)) provided by SEWA for the 13 DMAs were the daily average pressure and flow from January to October in 2019. To represent the drops in pressure and flow, the following calculation was carried out for the 13 DMAs for each month:  
\[\mathrm{P_{drop}=P_{montly-aver}-P_{daily}} \tag{1}\]  
\[\mathrm{F_{drop}=F_{montly-aver}-F_{daily-aver}} \tag{2}\]  
Table 1 illustrates the drops in pressure and flow sample calculation for (DMA1) in January, and values higher than the monthly average are shown in bold. Figure 2 shows an example of the normalized daily fluctuations in the pressure and flow for DMA1 for January compared to the average pressure and flow. \begin{table}
\begin{tabular}{c c c c c} \hline \hline January & Pressure (bar) & Inflow (m\({}^{3}\)) & \({}^{\dagger}\)Avg Pressure \({}^{\dagger}\) & \({}^{\dagger}\)Avg Inflow \({}^{\dagger}\) \\  & & & (bar) & (m\({}^{3}\)) \\ \hline  
6 \\ \hline Averages & 3.52 & 676.45 & 0.46 & 54.4 \\ Min= & & & 0.07 & 3.55 \\ Max & & & 1.53 & 176.5 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Pressure and flow drop calculation.