Integrated surface - ground water interaction approaches that can account for water quantity and quality transport

Governing bodies across Australia and New Zealand are more and more looking at the interaction of surface water and groundwater resources as part of overall natural resource planning approaches. As part of the process of developing catchment management strategies and associated policies, catchment scale water quantity and quality modelling has become an essential tool to test policy options and management scenarios and to predict outcomes of environmental manipulations. Catchment management models targeting systems with both surface and groundwater influences are most useful if an integrated approach is taken where both surface water and groundwater interactions can be explicitly captured, even in a simplified manner, to explore options for managing conjunctive use and/or cumulative impacts of nutrients on receiving waterways. Integrated catchment models were constructed in the eWater Source modelling platform which has strong core functionality in hydrology, pollutant generation and water management modelling. Source has been designed specifically to enable customization via the use of plugins. In order to capture the surface water-groundwater interactions (including nutrient pathways through groundwater), a characteristic of many catchments, Jacobs has used several approaches for its representation. Approaches such as the inbuilt surface water-groundwater interaction methods within eWater Source, a custom simplified regional surface water-groundwater interaction model (Network Groundwater Model) and a coupled Source-Modflow model have all been used as part of project applications. Through the use of these project examples, this paper will discuss the use of these models, conceptual calculations and catchment applications in Australia and New Zealand as well as its application to the broader catchment modelling community for future management applications.