In recent years there has been growing concern about the impact of diffuse source pollution on river, estuarine and coastal water quality and particularly with regard to non-compliance of bathing waters. Climate change, and particularly more intense storms in the bathing season, has led to increased compliance failure of bathing waters, e.g. last summer saw widely publicised beach failure occurrences at Amroth and Rhyl. Hydro-environmental impact assessment modelling studies, regularly undertaken by specialist consulting environmental companies, are generally regarded as having two fundamental shortcomings in model simulations, which can lead to erromneous environmental impact assessment outcomes. These shortcomings will be addressed in this project and include: (i) improving the computational linking of catchment, river and estuarine-coastal models to ensure momentum and mass conservation across the link boundary, and (ii) improving the kinetic decay process representation in deterministic models, to include the impact of salinity, irradiance, turbidity and suspended sediment levels. The main aim of this research project will therefore be to develop and validate linked hydro-environmental deterministic models to predict improved fluxes and concentration levels of faecal bacterial from catchment to coast, using dynamic decay rates related to a range of primary variables. This main objective will be achieved by: (i) setting up linked catchment, river and estuary-coastal models to predict flow and solute transport processes from Cloud to Coast; (ii) linking these models through an Open MI system and refining the link to include momentum conservation; (iii) extending the Cardiff Research Centre's Severn and Ribble river basin models to include catchments, (iv) developing and testing the Severn model against scaled laboratory model data for conservative tracer measurements, obtained using an idealised catchment-river-estuary physical model at Cardiff University, (v) undertaking a detailed analysis of earlier field studies (undertaken by the main supervisor and Professor David Kay, Aberystwyth) on the impact of turbidity and sediment adsorption on bacterial levels in the Severn estuary, with the aim of developing new formulations linking bacterial concentration levels with: salinity, irradiance, turbidity and suspended sediment), (vi) including the new formulations for bacterial decay (in the form of T90 values) in the linked models for river and estuary-coastal systems and to investigate the sensitivity of the receiving water concentration levels to these parameters, and (vii) studying briefly the effects of various renewable energy structures in the Severn estuary (including the Severn Barrage) on the receiving water faecal bacterial levels, particularly in terms of establishing the impact of the new linking methodology and the dynamic decay rates on the predicted concentration levels. The outcomes from this study will be published in journal and conference papers and presented in talks and lectures on the Centre's activities relating to marine renewable energy and particularly for the Severn estuary.