The impacts of urban discharges on the hydrology and water quality of an urban watercourse

This paper presents the findings of a study which has investigated the effects of urban discharges upon the hydrology and water quality of a small urban watercourse located in north London. A variety of hydrological variables and water quality parameters were monitored at a site downstream of two surface water outfalls (SWOs) and two combined sewer overflows (CSOs). Precipitation volume was found to be highly correlated with the total storm discharge (r2 = 0.91) and the duration of storm flow (r2 = 0.93). Precipitation intensity displayed a 0.67 level of correlation with peak discharge volume. Aqueous loadings of biochemical oxygen demand (BOD), nitrate, chloride, total ammonia, suspended solids and total and dissolved zinc, copper, cadmium and lead, increased during the five monitored storm events. The highest increases in pollutant loadings compared with dry weather values were associated with BOD and suspended solids.