An assessment of non-revenue water for Norton Town in Zimbabwe.

Abstract

ABSTRACT Water is an important natural resource and urban water utilities in Southern Africa are facing challenges in the provision of potable water supply. Non-Revenue Water (NRW) is one of the challenges affecting water provision in developing countries. Norton Town Council is mandated by the government to provide safe and adequate water to the residents of Norton. The town is faced with a challenge of limited water supply, with a supply of 7 500m3/day against an estimated demand of 15000 m3/day. This is against a background of high NRW in the region. Therefore, this study sought to assess the extent of NRW for Norton and its components. An evaluation of possible strategies to control NRW was also done. To determine NRW for the town, historical data from 2004 to 2015 was collected and analysed. From the historical data comparison of the bulk water received and billed consumption volume was done to determine overall NRW. Partitioning of water losses was done through Minimum Night Flow (MNF) analysis focusing on two distinct zones of the town which are Galloway and Katanga-Ngoni. Norton town is characterised by intermittent supply, therefore to perform MNF the water supply system was manipulated in order to create continuous flows as recommended. The results obtained were true for the testing period and to correct for intermittent supply correction factors were applied. Correction factors were determined based on the leakage theory which relates pressure to leakage. To evaluate the operating practices in the water supply system qualitative and quantitative data was collected through key informant interviews, questionnaires and meter testing. Multi-Criteria Decision Analysis (MCDA) was used to evaluate strategies to control NRW. MCDA used the data and information collected in the study to determine criterion and objectives in the analysis. Results from the study showed that the average NRW for the town from 2004 to 2015 was 34 % which is above regional benchmarks of 20 % to 25 %. This was attributed to absence of active leakage management, high metering inaccuracies, partial water billing in some areas of the town and manual meter reading instead of use of available automated data loggers. Partial billing suggests that residents in those areas may have free access to water contributing to NRW. Meter testing showed that 73 % of the tested meters were under registering consumption. The average NRW for the two areas were 65 % for Galloway and 76 % for Katanga-Ngoni. Partitioning of water losses for Galloway revealed that real losses were 26 % and apparent losses 74 %. In Katanga-Ngoni, real losses were 35 % and apparent losses 65%. The apparent losses for both areas are above recommended limit range of 20 % to 40 %, indicating a poorly managed system in terms of billing and metering. Apparent losses were attributed to a poor metering system characterised by use of non-functional meters and absence of a regulatory policy on metering and billing. Management of the water supply system by the local authority is fragmented between the departments responsible for water supply. This has resulted in inefficient use of equipment and infrastructure provided for improving water management. Controlling commercial losses was ranked first as a strategy to control NRW followed by integrated management and reduction of physical water losses respectively. The recommendations were to update the customer database and improve on metering. It was also recommended that utilisation of available zonal meters and data loggers be done so that both apparent and real losses are controlled. The study also suggested integrated management of the water system so that departmental goals on water services are the same.