Hydropower is recognized globally as a clean, high-quality, and flexible renewable energy source and is playing an increasingly crucial role in helping achieve carbon emission reduction and providing flexibility to power systems. Focusing on hydropower generation, this chapter discusses the development status and introduces the main types of hydraulic turbines and hydropower plants. The chapter focuses and discusses detailed modeling of the hydropower plants with reservoirs, run-of-the-river plants, cascaded hydropower systems, and pumped storage plants in the context of optimized operation.