Water quality impacts of urbanisation: Evaluation of current research

Abstract

This report is the first in a series of reports focussing on the water quality impacts of urbanisation. The primary objectives of this report has been to critically review relevant published research, to identify important areas where there is a current lack of in-depth knowledge and to define future research directions. It is common knowledge that urbanisation can lead to significant water quantity and quality impacts. Past research into quantity impacts have resulted in an in-depth understanding of these issues and acceptable reliability in commonly available predictive approaches. However this is not the case for water quality impacts. The underlying processes and concepts relating to urban water quality are well known in a qualitative sense. However their quantification has proved to be extremely difficult. This is a major failure in most research studies. As a result, attempts to correlate land use to pollutant loadings have been inconclusive. A limitation in current urban water quality research is that the approaches adopted are strongly based in water quantity research undertaken in the past. The extension of these concepts and processes is not satisfactory due to the strong reliance on physical factors only and the limited recognition of chemical processes. Chemical processes exert a strong influence on urban stormwater quality characteristics. It is this neglect which can be primarily attributed to the often contradictory results reported in research studies and the strongly location specific nature of study outcomes. As such, this has led to significant constraints in defining the process kinetics of pollutant generation, transmission and dispersion such as pollutant build-up and wash-off. Consequently, the management of water quality impacts in urban areas has proven to be a difficult task. The effectiveness of commonly adopted management and structural measures is open to question. The contradictory research findings in relation to these measures clearly point to the significant role played by location specific factors influencing water quality rather than purely land use. A holistic approach is needed to safeguard the quality of receiving waters in urban areas. The current approach to urban water quality management is piecemeal and the benefits are only be marginal. It provides a false sense of achievement and even detracts attention from the more difficult challenges to be met to safeguard urban water quality. It is important to ensure the transferability of research outcomes for wider benefit and the relationships derived should facilitate this transfer. Future research directions have been proposed taking the above noted concerns into consideration.