The paper highlights the increasing international public concern relating to hydro-environmental issues and cites examples of some of the water quality problems now being considered by hydraulic engineers on a regular basis. The limitations and restrictions of both physical and numerical hydraulic models are discussed and concern is expressed with regard to the increasing use of numerical models being made by non-specialist engineers or scientists - often with little understanding of hydraulics and numerical methods - to assist in the planning and/or design of water quality related studies. General details are given of numerical models used for flow and water quality concentration predictions in coastal and inland hydraulic basins and two example research projects are described. In the first of these studies comparisons are made between dynamically and non-dynamically linked nested models, with the results indicating that in some circumstances nondynamically linked models can give inaccurate velocity field predictions. In the second example higher order accurate schemes are compared for modelling the advection of abrupt concentration gradients, with computational efficiency and simplicity often being important in hydraulic engineering studies where complex boundaries, often including flooding and drying, can cause added difficulties. Finally, the importance of basic original research is also highlighted, particularly as national and international research funding agencies place increasing emphasis on applied research.