Role of urban wetlands in improving catchment river water quality with implications for management

The theme for World Wetlands Day in 2024 is centred on the symbiotic relationship between wetlands and human wellbeing. The urban wetland, as a nature-based solution, notably intertwines with human activities, distinguishing itself among various wetland types. Examining urban wetlands through the aspect of water quality reveals their ability to purify nitrogen and phosphorus from water sources. However, human activities affect river water quality via various sources and processes within an urban environment, including land surface and wastewater discharge, exhibiting significant complexity. Understanding how urban wetlands interact with these processes and their impacts on water quality is needed. To explore the role of wetlands in integrated urban water quality management, our study enhanced the representation of nutrient processes in wetlands and incorporated it into the whole-water cycle simulation tool – the Water Systems Integration Modelling framework (WSIMOD). This is done by quantifying the wetland-urban system interactions within subcatchments, between subcatchments, and at the catchment scale. Our study aims to (1) evaluate urban wetland benefits in water quality improvement via statistical analysis; (2) simulate such impacts through integrated modelling; (3) explore the pipe connections of wetlands and their impacts on systems-level water quality improvement to inform design and management. Analysis of observed water quality data reveals that the nitrogen concentration in a catchment influenced by the urban wetlands network is reduced by approximately 18% to 28%, with the phosphorus concentration showing a reduction of about 4% to 11%. At a local scale, within a single subcatchment, the model is demonstrted to capture the water quality dynamics and the observed impacts well by validating against the sampling data. Furthermore, at a broader scale encompassing the entire catchment, the connectivity of urban wetlands through pipes is expected to achieve better system-level water quality performance. This research emphasises the need to explore how urban wetlands influence and are influenced by various water elements, informing future urban wetland design and management strategies.