Preface

The series of manuals on techniques describes procedures for planning and executing specialized work in mater-resources investigations. The material is grouped under major subject headings called books and further subdivided into sections and chapters; section A of book 3 is on surface-water techniques. The unit of publicntion, the chapter, is limited to n narrow field of subject matter. This format permits flexibility in revision and publication as the need arises. Provisional drafts of chapters are distributed to field offices of the US. Geological Survey for their use. These drafts are subject to revision because of experience in use or because of advnncement in knowledge, techniques, or equipment. After the technique described in a chapter is sufficiently developed, the chapter is published and is sold by t.he Superintendent of Documents, U.S