Development, Calibration and Further Data Requirements of the Sewer Flow Quality Model Mosqito

Abstract

MOSQITO is the initial version of a sever flow quality model being developed by Hydraulics Research Ltd and the Water Research Centre as part of the UK River Basin Management programme. MOSQITO I simulates the time-varying behaviour of suspended solids, biochemical oxygen demand, chemical oxygen demand, ammoniacal nitrogen and hydrogen sulphide on catchment surfaces and in sewer systems. The model produces discharge pollutographs for these determinands which can be used as input to a river water quality model. MOSQITO consists of four sub-models which represent washoff from catchment surfaces, foul water inflow, pollutant behaviour in pipes and channels, and pollutant behaviour in ancillary structures within drainage systems. These sub-models are linked to the flow simulation model incorporated in the WALLRUS package which is the latest computer implementation of the Wallingford Procedure. The rationale behind the model, its structure and its operational basis have been discussed elsewhere (Moys and Henderson, 1988) and are therefore described briefly so that emphasis can be placed on the aspects which follow. Calibration and verification of the model are being carried out using data from a variety of experimental catchments in the UK. These catchments have been selected to exhibit a wide range of characteristics and include separate and combined sewer systems. Results of the calibration work are presented together with illustrations of the performance of the various sub-models and the overall model.