Synthesising dry weather flow input hydrographs : a Maltese case study

Abstract

Dry weather flow (DWF) input hydrographs are an essential aspect of combined sewerage modelling. Collecting or deriving such hydrographs is not easy given problems of accurate data collection, location in the network and disaggregation of other flows. A method of synthesising DWF hydrographs is presented based on results from a diary survey of individual domestic appliance usage. Such a study has been carried out on 51 households in Malta and it is shown that the sample is a reasonable representation of the local population. Appliance volumes were found to be consistent with those in the literature with the possible exception of the bath. Daily per capita usage was also found to be comparable in magnitude. Detailed plots consisting of volumetric discharge for each appliance were produced illustrating the significant diurnal variations in usage. A template plot for the Maltese Isles was produced indicating a mean and peak usage of 1.1 and 2.7 l/s/1000 head respectively.