Estimating Domestic Water Consumption For Water Balance Calculation Using Statistical Sampling Methods

The determination of the total domestic water consumption to establish a water balance for individual supply zones or District Metered Areas (DMAs) is often not possible due to the lack of the required metering infrastructure. Especially in developing countries the full coverage with domestic water meters at household level to accurately measure, monitor and bill authorized water consumption is not common and the water consumption must be estimated. This paper presents an approach for estimating the total domestic water consumption in a DMA based on the measuring data of a given limited number of household meters using two statistical sampling methods, simple sampling and post-stratified-sampling. For stratification additional factors classifying the sampling unit are acquired at household level. The application of the approach is demonstrated for a DMA of the city of Tiruvannamalai, India. The consumption data from a sample of 46 households, which covers approx. 7.4% of the 666 connected households in the DMA (population: 3,078), is used to estimate the total water consumption. For post-stratification, the classifying factors are household occupancy and type of water supply (single or multiple supply sources), which are assumed to influence the domestic water consumption. Considering the measured system input the magnitude of the estimated total water consumption is found to be realistic by calculating a water balance to determine the water losses in the DMA.