The need to understand the impact of urbanisation and changing land use on water and solute mass balances in the groundwater underlying urban areas has been increasingly recognised over the past 25 years. Groundwater resources are now included, for example, as part of integrated urban water management (IUWM). Conceptual models for IUWM have recently included:
- the impact of urbanisation on the water balance
- the impact of urban stream restoration on groundwater supplied baseflow
- the potential to reduce groundwater supplied nutrients and pollutant loadings to receiving water bodies.
Globally, the implementation of water sensitive urban design (WSUD) technologies such as at source control systems (SCSs) has been strongly recommended to offset the impact of urbanisation on surface hydrology, nutrients, and pollutant export. However, we don’t properly understand how such systems affect shallow water tables, how artificially enhanced infiltrated water travels via the complex urban subsurface hydrology (known as urban karst), and how the altered subsurface hydrology affects nutrient discharge to water bodies.
The dynamics of the urban subsurface hydrology are complex. They are the result of the intricate conveyance system (which alters the pre-development soil properties), a variety of artificial recharge sources, and poorly characterised localised sources that were traditionally believed to be impervious (such as pavements, via cracks and joints). This complexity of the urban subsurface hydrology is acute in catchments with significant groundwatersurface water interactions, and it has implications for nutrient fate and transport. Yet, while recent literature reviews recognise these issues as key knowledge gaps and challenges, the issues have received little attention in areas with high groundwater.