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Ewa Ociepa
Czestochowa University of Technology, Poland
corresponding author’s e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.

Abstract
The paper presents the analysis and evaluation of water losses in the distribution system used by the Water and Sewage Company in Końskie, Poland. The analysis of water losses was conducted based on the use of numerous indices that provide objective information on the condition of the water supply system. The method of the percentage water loss index was extended by the methods of determination of water losses according to the International Water Association (IWA). The data needed for the calculation of water losses, such as the amount of water supplied to the network, the wa-ter sold, water used for the company's own needs, the length of the network, the number and length of water supply con-nections, number of customers, mean pressure in the network, and number of failures was derived from Water and Sew-age Company in Końskie, Poland. These data were used to calculate the amount of water losses in individual years, per-centage water loss index (PWS), and the indices recommended by the International Water Association (IWA): Real Leak-age Balance (RLB), Non-Revenue Water Basic (NRWB), Unavoidable Annual Real Losses (UARL), Infrastructure Leak-age Index (ILI) and unit indices of loss per capita and per kilometre of network. Due to the likely relationships of the load and failure rate of the network with water losses, the failure intensity index and index of hydraulic load to the network.

The results of the analysis showed that with its comprehensive activities, the company has significantly reduced its water losses in recent years. Currently, most of the water loss indices have reached a level considered good compared to the national data and average according to the standards used in Western European countries. In 2012, most of the analysed loss indices were at a high or even very high level and showed higher than the national average loss of network water. The decrease of the NRWB index from 29% in 2012 to ca. 18% in 2018, and the decrease of the ILI value in the respective years from 3.1 to 1.5-1.6 indicate the effective countermeasures used to limit water losses. Currently, the value of IMI according to strict IWA criteria suggests a very good condition of the network. RLB2 is another indicator that fell sharply over the period analysed. In 2012, its value was more than twice as high as at present. On the other hand, the av-erage condition of the network is indicated by the unit water loss index per capita, which amounted to 52.80 in 2012 and currently is about 23.07 dm3/(inhabitant day). Very low values of the failure intensity index of the water supply system indicate that the impact of failures on water losses is insignificant, assuming that the company responds quickly to re-move identified leaks and there are no undetected failures.

The several years of analysis and evaluation of numerous indices of water loss presented in the paper reveals the effectiveness of the adopted strategies of reducing leakages in the distribution system. It should be noted that the compa-ny has been involved in comprehensive activities aimed at limitation of water losses for several years.

Keywords 
water losses, percentage water loss index, infrastructure leakage index, unit water start index, failure intensity index

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