This book consists of 9 chapters. Chapter 1: the developments in hydrology, the hydrologic cycle and its components. Chapter 2: the atmosphere with the formation and types of precipitation, measurement of precipitation and the determination of average precipitation, intensity-duration-frequency curves, frequency analysis and probable maximum precipitation. Chapter 3: evaporation and transpiration measurement of evaporation. Chapter 4: infiltration, factors influencing infiltration, measurement and estimation methods. Chapter 5: groundwater occurrences, groundwater movement and groundwater equations. Chapter 6: surface water and covers, factors affecting runoff, hydrometric measurement using various methods, rating curves, sediment measurement, sediment water relationships, hydrography analysis and reservoir storage analysis. Chapter 7: flood routing. It covers the basic equations, hydrologic storage and channel routing. Chapter 8: rainfall-runoff modeling, types of rainfall-runoff models, components and construction model. Chapter 9: floods and starts with definition of floods, causes of floods, the design flood.