Water quality model is a powerful toolbox for water quality research and management. At NERI, a state-of-the-art series of water quality models have been developed for use in Singapore and other regions. These models simulate the transport and fate of complex contaminants (e.g., antibiotics, antibiotic resistance, faecal bacteria, harmful algal blooms, pharmaceuticals and personal care products, endocrine-disrupting chemicals, plastics etc) in the aquatic environment. The models have been successfully applied in local reservoirs and coastal waters.