Integrated surface water-groundwater modelling : linking surface water and groundwater using DIVAST-SG

Surface-water and groundwater are two resources both requiring careful management and protection. Computer modelling of both has long been used as an aid to their management. Historically they have been modelled separately, as their behaviour is represented by different mathematical equations. However, in reality, they are a linked resource each affects the other. DIVAST is a two-dimensional hydrodynamic and water quality numerical model developed for estuarine and coastal modelling. The original model enables the simulation of problems such as pollution and flooding in surface waters. In this study the existing model is extended to allow the modelling of groundwater as well as surface water in the same model. Chapters 1-5 introduce the problem, review some existing models, and then derive, discretise, and implement the equations for surface water and groundwater flow into the new model. Chapters 6-10 test the new model against analytical solutions, laboratory data, field data, and an existing groundwater model (MODFLOW). The outcome is a new version of the DIVAST model, known as DIVAST-SG (Depth Integrated Velocities And Solute Transport in Surface water and Groundwater). It simulates interactions between two-dimensional surface water and groundwater, in addition to the facilities of the original code. The equations are solved within one model, avoiding coupling problems. It is successfully tested against analytical solutions, laboratory studies and field data, and compared to an existing groundwater code, where it successfully models a gravel aquifer adjacent to tidal surface water. A framework is laid for continuing this work to produce a pseudo 3-D surface- water / groundwater code. In addition, novel techniques are pioneered in the laboratory, where open cell foam is used in a tidal flume to represent a porous aquifer adjacent to a river, and a highly detailed dataset of groundwater field data is compiled in the course of the work.