Analysis of the factors influencing the fluctuation of non-revenue water in Luangprabang City, Laos

Non-revenue water (NRW) in Luangprabang City, Laos, has been high and fluctuating. Therefore, we aimed to analyze the factors influencing the fluctuation of NRW in two district-metered areas (DMAs). The average NRWs for 16–17 months in DMA-1 and DMA-2 were 28.92 and 43.92%, respectively, whereas the coefficients of variations of the monthly NRWs were high at 49.7 and 11.7%, respectively. Among the factors causing the fluctuation of NRW, meter inaccuracies were less than 2%, although inaccessibility to customer meters was high at 46.4 and 38.7% in DMA-1 and DMA-2, respectively. However, the meter reading intervals had little influence on billed water consumption. Using the IWA Water Balance table, the apparent loss was estimated as 2.6%, whereas the real loss (24.9%) was the main component of NRW (27.5%) in DMA-2. The monthly and 3–7-month moving averages of NRW were inversely correlated with billed water consumption, indicating that both volumetric and percentage NRWs were strongly influenced by fluctuations in billed water consumption. Network simulation verified that high inaccessibility to customer meters, particularly during the COVID-19 lockdown, caused large fluctuations in billed water consumption and NRWs. Therefore, access to customer water meters should be improved to alleviate the fluctuation of NRW.