Segmentation of the drinking water distribution network combined with a meter installation programme as the foundation to reduce non-revenue water (NRW) in Tizi Ouzou, Algeria
This was a pilot project to determine the importance of various factors involved in the successful reduction of non-revenue water (NRW). It helped in providing reliable statistics and in evaluating the impact of a meter installation program. Even though large-scale, active leakage management was not part of the project, network segmentation, mapping and the installation of meters provided the foundation of improved management of NRW. The achieved results can help to generalise and spread the experience to the other sectors of Tizi Ouzou and other parts of Algeria.
Case description and analysis
The supply of drinking water to Tizi Ouzou (100 km east of Algiers) is ensured by a hydraulic system consisting of 18 wells, 10 pumping stations, 16 storage tanks, a 64-km supply network and a linear distribution network of 167 km. The interconnected distribution network of Tizi Ouzou consists of 31,000 metres of pipelines made of different materials (asbestos cement, steel, cast iron, high-density polyethylene).
The public water service is managed by two centres, one for production (ABH) and one for distribution (ADE), and commercially by two customer agencies. Together they manage a portfolio of approximately 31,500 subscribers, representing a network connected to approximately 200,000 inhabitants.
The distribution sector of Tizi Ouzou covered by this case study satisfies the drinking water requirements of a population of 33,000 inhabitants, divided into 13 districts, representing 5,100 subscribers, 950 of which used to be charged at a fixed rate. In terms of water loss, as of December 31, 2008, the ratio of invoiced and produced volumes was 40 percent, indicating high levels of NRW.
The absence of reliable statistics on the performance of various network segments impeded decision making on the most attractive measures to stem the flow of NRW. The intent of this case study was to improve this information basis, and to contribute to some initial reduction of NRW.
Within the project, it was decided in a first step to divide the city network into nine sectors. Detailed execution and analysis focused on Sector 4 where the following four actions took place:
- Installing a large-diameter meter at the start of each tank
- Updating the network geographic information system
- Updating the subscriber files after a thorough investigation
- Replacing 1,300 individual meters with new ones to improve the accuracy of metering
The assessment of the pilot project concerned only one sub-sector in Sector 4, namely, "July 5 City" — with nearly 2,000 inhabitants per 300 subscribers. The expected gains in terms of reduction of NRW were evaluated (see tables in the next section). Eight actions were completed to achieve greater network control:
- Installing a block valve and a large diameter meter at the starting point of the distribution network - Checking the tightness of the isolation valves (to be set within prescribed limits of the sub-sector) - Carrying out moderate leak detection and repair operations - Implementing some rehabilitation works - Installing a valve and meter at the city entrance to measure incoming volume - Installing dividing meters at the entrance of each city building - Controlling individual meters, which resulted in sealing all counters to deter fraud and; - Replacing 171 meters with new ones.
This practice had numerous positive impacts, such as:
- 3% improvement (i.e. reduced losses) in network performance;
- 8% improvement in invoiced volume, due to more accurate metering; and
- 9% corresponding increase in revenues.
These physical changes also improved the financial position of the company, as higher revenues accompanied declining operating costs due to lower NRW.
While the results are encouraging, carrying out a large-scale network rehabilitation and improvement programme requires major capital investments that are not available within the water utility. However, the success of this pilot project encouraged the Algerian government to launch a massive study project for the diagnosis and rehabilitation of drinking water supply systems of 43 major cities managed by ADE.
-Better network management through the use of acquired facilities
-Continuous monitoring of distributed volumes
- A reliable customer database, owing to the update of the subscriber files
- 3% improvement (i.e. reduced losses) in network performance
- 8% improvement in invoiced volume, due to more accurate metering
- 9% corresponding increase in revenues
Based on human, material and financial resources, the pilot project was successful. Strong administrative, technical and managerial skills to identify, diagnose and map networks were needed to achieve the pilot project’s aims.
31,500 subscribers; daily supply of 200 litres per capita; daily distribution volume of approximately 41,000 m3 — or a quarterly volume of around 3.7 million m3
The intent was to apply the pilot project to other sectors of Tizi Ouzou once the experience was considered successful. On a large scale, the reduction of NRW exceeded the financial capacity of the water management company of Tizi Ouzou; thus, they require major funding from the state.
- Around 65,000 were used to by network equipment (isolation valves, large and small-diameter meters). Current operating costs related to GIS upgrade, updating subscriber files, and works for leak detection and repair are added to this financing.
Mr Larbi Baghdali
- Ministry of water resources, “Specification standard for the management by concession of the public service of drinking water supply and regulations thereunder,” Official Gazette of the Algerian Republic, no. 8, pp. 12-21 (February 2008).
- Hattoum, Y. and Bouayad A., “Commercial aggregates of sector 4,” ADE area of Tizi-Ouzou (2008).
- Hattoum, Y. and Bouayad A., “Sectorization works in the city of Tizi-Ouzou,” Internal report: ADE area of Tizi-Ouzou” (2010).
- Silhadi, S., “Operating balance,” Internal memo, ADE, Directorate General, Algiers (2011).
- ADE, “Goals and action plan for the operation,” Internal policy memorandum (2013).
- ADE, Directorate General, Algiers (2011).
- http://www.ipemed.coop/adminIpemed/media/fich_article/1384435889_Etat%20des%20lieux%20du%20secteur %20de%20l'eau%20en%20Alg%C3%A9rie_oct2013.pdf