The book 'A Textbook of HYDROLOGY' presents the subject matter of Hydrology in a lucid. It covers the syllabus prescribed for the subject of Hydrology by almost all the Universities. This book can be used by both Undergraduate and Graduate students and also the Teachers alike. The end of the chapter exercises are provided under three categories namely descriptive, analytical and objective which will be highly useful to the readers to test their comprehension of the subject. The various processes of Hydrological cycle like Precipitation, Evaporation, Transpiration, Infiltration, Run-off, Storage, Ground Water etc., are treated systematically and in a logical sequence. The methods of analysis and interpretation of Hydrological data are presented in an un-ambiguous manner and their design applications are demonstrated through well formulated worked out examples. For this reason the book should be useful for both students as well as practicing engineers dealing with Hydrological design of Water Resource projects.