Alternative Method for Nonrevenue Water Component Assessment

This paper presents a practical method for estimating the volume of apparent losses in water supply systems, particularly in a developing country context, so that real losses can be calculated from the volume of nonrevenue water (NRW). The method employs the fact that almost all apparent losses reach wastewater treatment plants (WWTPs). The volume of apparent losses can be estimated through establishing a water and wastewater balance using routine measurements of WWTP inflow and routine data of billed consumption. The water and wastewater balance was applied in the water supply system of Sana’a, Yemen, so NRW components were estimated. Sensitivity and uncertainty analyses show that all sources of the errors are small apart from the level of accuracy of measuring the WWTP inflow, and this accuracy can be practically improved. Other parameters and variables are relatively insensitive. The paper discusses the advantages and limitations of the suggested alternative method compared with the other NRW assessment methods.