Influence of construction works on urban streamflow water quality variations

Construction activities can have long-lasting impacts on receiving water bodies, especially when they receive polluted urban runoff. Therefore, it is essential to minimize these impacts on water quality and consider the long-term environmental effects of development activities. This study aims to provide insights into the assessment, temporal variations, and key variables associated with the impact of construction works on streamflow water quality. However, current assessment methods relating to construction works and streamflow water quality may lead to spurious correlations. A spurious correlation refers to a connection between two variables that appears to be causal but is not. This study proposes a novel approach to avoid spurious correlations between construction work signatures and water quality, ensuring causality and correlation between water quality parameters. The approach was applied to a developing urban catchment in Hong Kong. Compared to existing assessment models, the proposed approach advances in ensuring true correlations between construction works and streamflow water quality. It is also the first to develop a new indicator to represent the key variable of construction works. In this study, salinity, turbidity, and suspended solids were used as substitutes for construction activity parameters, such as the number of construction works, to correlate with water quality parameters. Additionally, principal component analysis and the construction work signature index were both adopted to calculate the key variables of water quality on behalf of construction works. Results demonstrate that the new approach has significantly improved causality by 45 % compared to previous assessment methods. However, the method has limitations as it does not consider the impact of rainfall on construction works.