AN INTEGRATED MODELLING FRAMEWORK TO SIMULATE UNSTEADY FLOW AND REACTIVE-TRANSPORT FOR URBAN RIVER-AQUIFER SYSTEMS

Abstract

Stream-aquifer flow exchange has been traditionally measured directly through seepage meters installed in the streambed or estimated indirectly from field water quality and quantity observations. However, such methods can only provide rough average estimations and are unsuitable for prognostic studies. Catchment scale models as well as single environmental compartment models (e.g. groundwater models) in combination with field observations offer an alternative to obtain a more detailed estimation of stream-aquifer fluxes over space and time. Yet, over the past decade it has been recognized the need for more physics-based estimations for both fundamental and applied research. As a result, a few mechanistic river-aquifer flow interaction models have been developed but none provide a framework to look at the exchange of contaminants, which is an increasing problem particularly in urban areas. In this study, a new modelling framework (FLUXOS) was developed to provide a physics-based, distributed and time-dependent estimation of contaminant exchange between rivers and aquifers. The new tool was validated numerically against analytical solutions and applied to 2 real world cases. Field observations were collected to calibrate and validate the model. FLUXOS and other single-compartment model outputs were also compared.