Water resources engineering is the quantitative study of the hydro-logic cycle the distribution and circulation of water linking the earths atmosphere, land and oceans. Surface runoff is measured as the difference between precipitation and abstractions, such as infiltration (which replenishes groundwater flow), surface storage and evapora-tion. Applications include the management of the urban water supply, the design of urban storm-sewer systems, and fl ood forecasting. Hydraulic engineering consists of the application of fluid mechanics to water flowing in an isolated environment (pipe, pump) or in an open channel (river, lake, and ocean). Civil engineers are primarily concerned with open channel flow, which is governed by the interde-pendent interaction between the water and the channel. The purposes of this book, includes both water use and water excess management. The fundamental water resources engineering process-es are the hydrologic processes and the hydraulic processes. The hy-drologic processes include rainfall, evaporation, infiltration, rainfall-runoff and routing, all of which can be further subdivided into other processes. Knowledge of the hydrologic and hydraulic processes is extended to the design and analysis aspects. Water resources development has had a long history basically begining when humans changed from being hunters and food gatherers to developing of agriculture and settlements. This book builds on that knowledge to present state-of-the-art concepts and practices in water resources engineering.