Publisher Summary This chapter introduces the planning and management of water resources systems. An overview of the current status of water resources utilization and the likely scenario of demands in the near future are discussed. The basic concepts, practical applications, and advantages and disadvantages of systems analysis techniques are presented. Also provided is a discussion of seven challenges for the water sector identified and debated in recent international forums. The chapter also discusses decision making. Optimization and simulation techniques are discussed. Most of the analysis dealing with planning and management of water resources systems is carried out using these techniques. Besides technical aspects, economic analysis is essential to rank the various competing projects and the subsequent approval by the decision-maker. Planning and development of water resources are then discussed and systems operation and management are explained.