Reservoir construction is the key strategy for water resource management. In recent years, the migration of pollutants and their transformation into the reservoir ecosystem has become a global problem. Intensified anthropogenic activities and unsustainable practices have amplified the pollutant levels in the reservoir. Therefore, this book intends to highlight environmental characteristics of the reservoir, study methods of ecotoxicology, and mechanistic toxicogenetic pathways of pollutants in the reservoir. Adverse outcome pathway (AOPs) model is used to elucidate toxicological effects of reservoir pollutants. Moreover, ecological and human health risks of the Three Gorges Reservoir (TGR), the largest power generation reservoir on earth, and its pollution status are also discussed.