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Proceeding Paper

Determination of Infrastructure Leakage Index (ILI) Using Analyses of Minimum Night Flows †

by
Monika Polachova
* and
Ladislav Tuhovcak
Institute of Municipal Water Management, Brno University of Technology, 602 00 Brno, Czech Republic
*
Author to whom correspondence should be addressed.
Presented at the 3rd International Joint Conference on Water Distribution Systems Analysis & Computing and Control for the Water Industry (WDSA/CCWI 2024), Ferrara, Italy, 1–4 July 2024.
Eng. Proc. 2024, 69(1), 211; https://doi.org/10.3390/engproc2024069211
Published: 4 December 2024

Abstract

:
The article presents in detail a proposed methodology for ILI estimation based on the analysis and measurement of minimum nighttime flow, along with results of the application of the methodology. The methodology responds to the EU directive referred to below.

1. Introduction

At the end of 2020, after a long discussion, a new DIRECTIVE (EU) 2020/2184 OF THE EUROPEAN PARLIAMENT AND OF THE COUNCIL on the quality of water intended for human consumption was approved. In Article 4, the directive sets a requirement for EU member states to assess water leakage levels in their territories and the potential for improvement using a method based on the infrastructural leakage index (ILI) or another suitable method. Results of the assessment should be communicated to the Commission by 12 January 2026 [1].
In the Czech Republic, the water supply infrastructure is owned by municipalities and cities (more than 5000 entities). The infrastructure is operated by over 2,000 operators. At the same time, approximately 50 of the largest water utility companies supply water to more than 95% of the population. In the last 20 years, a lot of attention has been focused on reduction of water losses. Many large water utility companies today report water losses of less than 10% of Revenue Water. The most common technical indicator of water losses is unit leakage expressed in m3/km/year. In recent years, most large water utilities have reported the value of this indicator at 2000 m3/km/year. There is not much experience in the Czech Republic with the use of water balance according to IWA methodology, and the ILI indicator is determined with an empirical formula using, among other things, the length of water connections and the average operating pressure [2].

2. Methodology for ILI Evaluation Based on Minimum Night Flows

A new methodology was developed to determine the ILI for individual water distribution systems (WDS), pressure zones and measurement areas (DMAs) based on minimum nighttime flow analyses. The methodology is based on a Minimum Night Flow (MNF) analysis with measurement of actual water consumption during night hours using Smart Water Meters [3].
Basic information for evaluation of MNF is data on inflow to the zone that can be obtained from a Water Meter between a water tank and a consumption point. The readings provide information about the minimum night flows that generally occur between 2 a.m. and 4 a.m.
The proposed methodology for ILI determination was assessed and validated for five different water supply systems: three hydraulically separated pressure zones of a selected water supply system of a large city (approximately 380,000 inhabitants) and two water supply systems in small municipalities. The following information will cover only one of the three DMAs of the large city (DMA 1).

2.1. MNF Decomposition

The minimum night flow QMNF consists of three components [4] (Figure 1):
  • Actual consumption of customers;
  • Real losses (RL);
  • Unavoidable real losses (URL).

2.1.1. Actual Consumption

To determine actual consumption in a pressure zone, it is ideal to have data available on consumption over time, which can be monitored, e.g., by Smart Water Meters installed at individual connections [4].

2.1.2. Unavoidable Real Losses

They represent a fixed component of actual losses. URL can be read from the relevant table based on the number of connections per km of the network and the average operating pressure in kPa, or they may be calculated [4].

2.1.3. Real Losses

Real water losses can be described as water passed through a water pipe minus actual consumption (both billed water and possibly water used by the operator). An integral part of real losses are unavoidable real losses, which represent a kind of limit to which real losses can be successfully reduced [4].

2.2. Approximate Recommended MNF Values and ILI Determination

The approximate recommended MNF values for a given specific nighttime hour should be about 0.8–1.0% of average daily consumption Qp. For a full day (24 h), this amounts to 19.2–24.0% of average daily consumption Qp [L/s]. Unavoidable real losses should be about 1/3 of MNF [5].
This means the following:
URL = 6.4–8% Qp
This assumption implies that it is possible to approximately determine the ILI value and thus avoid the empirical formula for determination of the ILI [6].
The ILI can be obtained from the following formula:
ILI = RL/URL
where ILI is the infrastructure leakage index [-]; RL is the real losses of water [%]; and URL is the unavoidable real losses value in ranging (1).

3. Determination of Actual Consumption from Smart Water Meters

As stated, actual consumption can be ideally determined from Smart Water Meters in the monitored DMA. In DMA 1, this was possible as the connections in this DMA are mostly fitted with Smart Water Meters.

3.1. Description of Smart Water Meters

There are pulse sensors and Flostar or Sensus transmitters installed on each Water Meter. The antennas and receivers are SUEZ technology. Transmission is at 169 MHz radio frequency and the data are acquired every 6 h.

3.2. Form of the Data Collected from Smart Water Meters

Measurements of average flow rates taken every 15 min after the water tank in DMA 1 were obtained and plotted against time. The selected period was from 1 September 2023 to 31 October 2023. After processing the data, it was possible to determine the characteristic flows from the water tank. In DMA 1, most of the connections (154 out of 161) are fitted with Smart Water Meters. Consumption data were monitored from 1 September 2023 to 31 October 2023. One Excel sheet was extracted from each Smart Water Meter in the network with flow rates recorded every 6 h (154 .xlsx files in total).

3.3. Data Processing

Since the readings were available in 6 h periods, individual Smart Water Meters were grouped and then the data measured during the MNF period were plotted. To meaningfully divide the 6 h periods at least into individual hours, daily flow into the network measured after the water tank was used. An example of the percentage distribution of flows during individual hours of the day is shown in Figure 2.

4. Outputs and Evaluation

Since DMA 1 is mostly fitted with Smart Water Meters, it was possible to calculate losses based on knowledge of both the MNF values in the form of Qp,MNF, which represents the average flow from the water tank between 2:00 and 4:00, total average flow Qp and actual consumption QSM measured at the Smart Water Meters.

4.1. Real Losses

Real losses can be determined by simple subtraction:
RL = Qp,MNF − QSM,MNF
where RL is the real losses of water [L/s]; Qp,MNF is the average inflow to the network at the time of MNF [L/s]; and QSM,MNF is the average consumption at the time of MNF [L/s].

4.2. MNF Decomposition

There is only a minimal difference between inflow into the water supply network and actual consumption in DMA 1. This fact indicates a minimum proportion of real losses and, in accordance with the proposed methodology, we can conclude without further calculations that in this case real losses (RL) are equal to unavoidable real losses (URL). Therefore, ILI equals one. When using the empirical formula for ILI calculation, the ILI value in DMA 1 was 2.18. Other possible formulas for ILI calculation were also used and the ILI values ranged between 1.12 and 1.49.

5. Conclusions

For the tested sites, the calculated ILI values ranged from 1 to 2.18. The ILI value was calculated for all selected sites, with different calculation procedures chosen for possible comparison. The work also proposes a methodology for ILI determination based on minimum night flows, which is based on MNP decomposition and determination of real losses. Correctness of the calculation of losses according to the methodology was verified according to actual data from the operators of the water supply systems in question for individual years. In all cases, determined losses according to the methodology corresponded to the average values of losses reported by the operators in annual summaries. A more efficient use of Smart Water Meters could be ensured with a different frequency of readings at least during MNF (2:00–4:00), where the data would be read, e.g., at least every hour, and thus it would be easier to determine consumption patterns and compare them with inflow to the network. Based on this study, it is recommended to reduce URL values, for example, to the range of 4–6% Qp. Further testing and validation are needed for accurate determination for specific types of WDS.

Author Contributions

Conceptualization, L.T. and M.P.; methodology, M.P.; validation, M.P.; formal analysis, M.P.; investigation, M.P.; resources, M.P.; data curation, M.P.; writing—original draft preparation, M.P.; writing—review and editing, M.P.; visualization, M.P.; supervision, L.T. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

Suggested data are available from the authors of the paper.

Conflicts of Interest

The authors declare no conflicts of interest.

References

  1. Directive (EU) 2020/2184 of the European Parliament and of the Council of 16 December 2020 on the Quality of Water Intended for Human Consumption. Available online: http://data.europa.eu/eli/dir/2020/2184/oj (accessed on 2 September 2024).
  2. Benchmarking VaK: Report for 2021. The Ministry of Agriculture of the Czech Republic. 2021. Available online: https://eagri.cz/public/web/mze/voda/vodovody-a-kanalizace/benchmarkingvak/zprava-za-rok-2021 (accessed on 2 September 2024).
  3. Polachova, M. Vyhodnocení Ztrát Vody na Území Města Brna. Diploma Thesis, Brno University of Technology, Brno, Czech Republic, 2024. [Google Scholar]
  4. Hamilton, S.; Mckenzie, R.S. Water Management and Water Loss; IWA Publishing: London, UK, 2014; ISBN 978-1-78040-635-0. [Google Scholar]
  5. IWA. International Water Association. 2023. Available online: https://iwanetwork.org/ (accessed on 2 September 2024).
  6. Global ILIs. Regional Summaries of Infrastructure Leakage Index. Online. The LEAKSSuite Library. 2019. Available online: https://www.leakssuitelibrary.com/global-ilis/ (accessed on 2 September 2024).
Figure 1. The three components of MNF [4].
Figure 1. The three components of MNF [4].
Engproc 69 00211 g001
Figure 2. Example of percentage distribution (for Group I) [3].
Figure 2. Example of percentage distribution (for Group I) [3].
Engproc 69 00211 g002
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Share and Cite

MDPI and ACS Style

Polachova, M.; Tuhovcak, L. Determination of Infrastructure Leakage Index (ILI) Using Analyses of Minimum Night Flows. Eng. Proc. 2024, 69, 211. https://doi.org/10.3390/engproc2024069211

AMA Style

Polachova M, Tuhovcak L. Determination of Infrastructure Leakage Index (ILI) Using Analyses of Minimum Night Flows. Engineering Proceedings. 2024; 69(1):211. https://doi.org/10.3390/engproc2024069211

Chicago/Turabian Style

Polachova, Monika, and Ladislav Tuhovcak. 2024. "Determination of Infrastructure Leakage Index (ILI) Using Analyses of Minimum Night Flows" Engineering Proceedings 69, no. 1: 211. https://doi.org/10.3390/engproc2024069211

APA Style

Polachova, M., & Tuhovcak, L. (2024). Determination of Infrastructure Leakage Index (ILI) Using Analyses of Minimum Night Flows. Engineering Proceedings, 69(1), 211. https://doi.org/10.3390/engproc2024069211

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