The preparation of these two volumes results in part from the development of a course in Irrigation engineering presented at the University of California. It is based on an acquaintance with a large number of irrigation systems, located in most of the States of the western part of the United States and in western Canada, Obtained through many Opportunities for examination of these projects and through connection with a number of them. The writer has not confined himself to his own experience and observations, but has discussed the principles of irrigation engineering presented in this work with a number of successful engineers, who have had much experience in the construction and Operation of irrigation systems. He has also availed himself not only of contemporary literature pertaining to American Irrigation engineering, but has consulted a large collection of foreign publications, mostly from India, Egypt, Spain and France. While there is still considerable difference of Opinion among engineers regarding some of the principles of design of irrigation works, it is believed that the Opinions and principles presented are in accordance with correct theory and good practice as demonstrated by careful observation.