I am happy to present the book entitled, "Hydrology and Irrigation Engineering" to the Students of Civil Engineering and Environmental Engineering and also to the students preparing for competitive Examinations. The course content has been planned in such a way that the general requirements of all Engineering students are fulfilled. During my experience of teaching this subject to undergraduate and post-graduate Engineering students, I have observed that the students face difficulty in understanding clearly the basic principles, fundamental concepts. To meet this very basic requirements to the students, a large number of the questions taken from the examinations of the various Universities of India and other professional and competitive examinations. The book is written in a simple and easy to follow language, so that even an average student can grasp the subject by self study. I am thankful to my family members, colleagues, friends, students who encouraged me to write this book.Every effort was made to eliminate errors in the text book, Suggestions from the readers for the improvement in the book will be most gratefully acknowledged.