Coastal Reservoir Technology and Applications presents the analyses showing that the world is not running out of water, but water is running out of river mouths—we need to work to harness this resource. Compared with inland water storages and desalination technology, coastal reservoirs are a nature-based water solution without disturbing the environment. This book mainly answers the questions of what the coastal reservoir technology is, where we should construct coastal reservoirs, and how to supply sufficient, high-quality and affordable water to the world with minimum environmental/social impacts. Chapter 1 reviews modes of water resources development in the history along with current problems and reasons. Chapter 2 discusses the definition of coastal reservoirs, its classifications and applications, and the SPP/downstream water management strategy. Other chapters analyse water crisis in every continent, as well as their water solutions. The possible coastal reservoir for each major river is suggested as well. Without freshwater, no one can survive. Likewise, without sufficient, high-quality and affordable freshwater, no community can achieve sustainable development. However, water is also a killer when it is too much (floods), too dirty (pollution), and too turbid. Different from other books, this resource shows how to solve these water problems. Coastal reservoirs and SPP strategy are suggested to develop floodwater in a safe way in coastal and inland regions, respectively. Solution of water-food-energy-ecosystem nexus needs a paradigm shift from upstream to downstream water management, i.e., from mountainous dams to coastal reservoirs, which conserves the precious, clean freshwater in seawater environment.