Journal of Spatial Hydrology Spring Vol. 5, No. 1 Spatial Analysis of Urban Stormwater Quality M. Ghafouri1 and C.E. Swain Abstract Urban stormwater non-point source pollutants are recognized as a major cause of receiving waters quality deterioration. To date most research has focused on specifying temporal variations of stormwater quality parameters which includes high uncertainties and also increases the risk of pollution control structures failure. Traditionally, the temporal variations of quality parameters in forms of either pollutograph or Event Mean Concentration (EMC) is obtained by sampling stormwater at the outlet of urban catchments for quality analysis in addition to measurement of flow rate over years. Spatial variations of the runoff quality are the key factor in non-point source pollution studies. This research investigates spatial variability of urban runoff quality parameters such as Total Phosphorous (TP), Total Nitrogen (TN), Suspended Solids (SS) and Biochemical Oxygen Demands (BOD) in relation to land use of urban catchments. In spatial analysis, stormwater will be sampled over the whole catchment area for a number of rainfall events during a year without any requirement to measure flow rate. This research showed comparable results for average pollutant concentrations with those of other urban catchments in Australia where traditional sampling method was used. The research outcomes will reliably estimate pollutants concentration for improved and efficient design of pollution control structures for each land use. KEY WORDS: Spatial analysis, temporal analysis, stormwater, Event Mean Concentration, geostatistics, pollutants Introduction Urbanisation, development and populating of an area create different pollutants, which are carried by stormwater to receiving waters, such as rivers and lakes, and deteriorate their quality and endanger their ecosystems. Urban stormwater, once was recognized as a major source of pollutants, is now considered as a valuable resource for non-drinking purposes in cities. Stormwater runoff from urban areas is a significant source of pollution to inland water bodies such as streams, rivers, and lakes (Thomas and Reese 1995). Despite existing systems of urban runoff collection and disposal, limited consideration has been given to the quality of stormwater runoff. Not only water flows into the river but also rubbish, animal droppings, chemicals, fertilizers, oils, soil and anything that is placed in or washes into street gutters can end up in the river, and polluting the environment (Allison et al. 1998).
Stormwater quality management of urban catchments covers a broad spectrum of issues related to municipal, industrial and amenity irrigation practices. The return flows from municipal and industrial uses, which are discharged from specific locations, are generally referred to as pointsource pollution. Water quality characteristics of these return flows can be easily monitored over time and if required, the discharge can be treated before entering receiving waters. To date most investigations conducted on runoff quality have focused on the estimation of point source pollutants and the effects they have on rivers water quality. Little attention has been given to different land uses such as residential, commercial, industrial and rural areas as sources of pollution. This kind of pollution is called non-point source or diffused pollution, which has been acknowledged as a major source of pollution to receiving waters (Novotny and Olem 1994).
Despite considerable stormwater volume being generated from urban catchments, pollutant concentrations and loads vary in relation to either land use or type of activity, which make their estimation for design of pollutant control structures very difficult. Complexity in estimation of the
1. School of Engineering and Technology, Deakin University, Geelong, Vic, 3217, Australia, firstname.lastname@example.org
diffused pollutants concentration...