Module –I

Hydrologic cycle, availability of water on earth, importance of hydrology and its applications in engineering, Precipitation: Forms & types, measurement of rainfall, optimum number of rain guage stations, consistency of rainfall data, presentation of precipitation data, mean aerial rainfall, depth – area duration curve, design storm, losses from precipitation, evaporation, and infiltration.

THE HYDROLOGICAL CYCLE

As a starting point for the study of hydrology it is useful to consider the hydrological cycle. This is a conceptual model of how water moves around between the earth and atmosphere in different states as a gas, liquid or solid. As with any conceptual model it contains many gross simplifications; these are discussed in this section. There are different scales that the hydrological cycle can be viewed at, but it is helpful to start at the large global scale and then move to the smaller hydrological unit of a river basin or catchment.