"This course is focused on applications of fluid mechanics that provide insight into the physics and transport in environmental systems. We will review some fundamental concepts of fluid mechanics such as Reynolds transport theorem. Then, we will go through pipe flows and open channel hydraulics. We will also learn the fundamentals of advection, diffusion, turbulence and mixing in stratified natural systems. Lakes, rivers and estuaries will be used as example environmental systems, which will be used to motivate investigations into fluid mechanics processes such as turbulence, internal waves, plumes, jets and convective mixing. Some special topics such as gravity current will be given. The course is designed to guide students through learning: 1) the qualitative descriptions of environmental flows 2) scaling analysis as a tool for understanding environmental systems 3) basic processes that control different typical Environmental fluid mechanics (EFM) flows"