Impact of global warming on urban stormwater quality: From the perspective of an alternative water resource

Abstract

Stormwater is a largely under-utilised resource available to alleviate water shortages in urban areas. However, stormwater needs treatment before use. Further, projected changes to rainfall patterns due to global warming will alter stormwater quality characteristics. This study projects potential changes to the primary source of stormwater degradation, namely, particulates that transport the largest fraction of toxic pollutants in stormwater. The results show that 1.5 °C and 2 °C warming can influence the increase in toxic pollutant loads (heavy metals) by more than 90% on urban surfaces and by nearly 50% in stormwater runoff. Stormwater quality will be further degraded under the upper limit of the projected changes to dry periods and precipitation in the context of Representative Concentration Pathway (RCP) 8.5. Compared to the present day, results indicate that cities in the future will face more challenging tasks in designing effective measures to address increasingly complex stormwater quality responses to different combinations of dry and wet weather conditions. Therefore, this study urges the need for achieving a paradigm shift in the accuracy of stormwater quality predictions by incorporating the effects of changing weather patterns into the current practice of stormwater quality modelling, and thereby to optimise urban stormwater management.