Quantification of water loss indices in a water distribution network: a case of water and sewerage company of Nairobi City, Kenya

The study focused on the quantification of water loss and leakages in a water distribution network (WDN). The study used international water loss indices to assess the status of the WDN of Nairobi City Water and Sewerage Company (NCWSC). Key findings for the period between 2014 and 2023 show that the unavoidable loss index improved by approximately 8.1% of the system input volume; the failure intensity index decreased by 0.74 failure/km/y; the waterloss index dropped by 4.11%; the loss-per-capita index dropped by 29.17 dm³/(inhabitant·day); the real leakage balance index reduced by 307.02 dm³/(connection·day); the non-revenue water (NRW) index dropped by 6.78%; and finally, the infrastructure leakage index (ILI) reduced by 2.154. These changes have been realized by NCWSC as a result of the innovative measures and strategies put in place to manage the issues of NRW. The WDN is classified as being in an inadmissible technical condition, as per the International Water Association recommended standards of ILI ≥ 3.5. On the other hand, the ILI values for the WDN fell within the range of 4.0 < ILI ≤ 8.0 for the World Bank Institute banding system for developing countries, which indicated a satisfactory technical state, whereas the American Water Works Association scope, 3.0 < ILI ≤ 5.0, was satisfied, indicating satisfactory network's technical condition.