Computer Modelling Techniques in Environmental Hydraulics and Water Resource Engineering

Computer modelling has become indispensable to environmental hydraulics and water resource engineering, where researchers and practitioners are increasingly required to analyse complex and dynamic water systems across a wide range of spatial and tem-poral scales. From hydraulic structures to water quality, catchment hydrology, and wa-ter-resources planning, computer models provide the basis for understanding physical processes, testing management strategies, and supporting engineering decision-making under uncertainties. As environmental pressures intensify due to climate change, growing human intervention, and increasing demands on water systems, the role of com-putational modelling has become both broader and more critical. At the same time, the methodological landscape of water modelling is evolving rap-idly. Physics-based modelling remains fundamental for faithfully representing hydraulic and hydrological mechanisms, loyally resolving flow and transport processes, and straightforwardly maintaining interpretability. However, conventional modelling ap-proaches are now increasingly complemented by optimisation techniques, uncertainty analyses, and data-driven methods, particularly in situations characterised by sparse ob-servations, high system complexity, and the necessity for timely operational predictions. Rather than replacing physics-based approaches, these emerging methods are re-shaping the field towards integrated computational frameworks in which mechanistic understanding, statistical inference, and algorithmic efficiency are considered in a com-plementary manner. This Special Issue, Computer Modelling Techniques in Environmental Hydraulics and Wa-ter Resource Engineering, reflects the aforementioned transition clearly. It focuses on math-ematical modelling and numerical simulations in environmental hydraulics and water resource engineering, while also encouraging the integration of artificial intelligence (AI) into conventional computational modelling. The papers collected in this issue provide a timely overview of current advances in the field, spanning process-based hydraulic and water-quality modelling, optimisation and infrastructure designs, data-driven forecasting, uncertainty analyses, and evidence syntheses. Taken together, these contributions show that contemporary water modelling is becoming more computationally sophisticated, more integrated, more adaptive, and more closely relevant to decision-making.