United States Department of Part 650 Engineering Field Handbook Agriculture Natural National Engineering Handbook Resources Conservation Service Chapter 14 Water Management (Drainage) Chapter 14 Water Management (Drainage) Part 650 Engineering Field Handbook Issued April 2001 Acknowledgments This chapter was prepared under the general direction of Ronald L. Marlow, national water management engineer, Natural Resources Conserva- tion Service (NRCS), Washington, DC, with assistance from Patrick H. Willey, agricultural engineer, NRCS, Portland, Oregon. Extensive drafting was previously done by Richard D. Wenberg, retired national drainage engineer, with assistance from John Rice, Walter K. Twitty, Gordon Stroup, Elwin Ross, and Virgil Backlund, retired water management engineers (drainage). Editorial and layout assistance was provided by Mary Mattinson, NRCS, Fort Worth, Texas. The final revision were prepared by Walter J. Ochs, Richard D. Wenberg, and Bishay G. Bishay, water management engineering consultants. Peer reviews were provided by James E. Ayars, agricultural engineer, USDA ARS, Pacific West Area, Fresno, California, and Norman R. Fausey, soil scientist - research leader, USDA ARS, Midwest Area, Columbus, Ohio. Reviewers within NRCS include: Gordon Klofstad, national construction engineer, William Hughey, national agricultural engineer, William Irwin, national design engineer, John S. Moore, national hydrogeologist, and Donald Woodward, national hydraulic engineer, Washington, D.C. John Andrews, Denver, Colorado, Grady Adkins, Columbia, South Caro- lina, Arthur Brate, Columbus, Ohio, Dennis Carman, Little Rock, Arkan- sas, Walter Grajko, Syracuse, New York, Ronald Gronwald, Dover Dela- ware, Mark Jensen, Des Moines, Iowa, Richard Judy, Morgantown, West Virginia, Tillman Marshall, Richmond, Virginia, Perry Oakes, Auburn, Alabama, John Ourada, Salina, Kansas, Allen Stahl, Annapolis, Maryland, Jesse Wilson, Gainesville, Florida, all state conservation engineers with their respective staffs. Michelle Burke, Brookings, South Dakota, Gene Nimmer, Juneau, Wiscon- sin, and Chris Stoner, Stillwater, Oklahoma, all agricultural engineers. Jim Bickford, irrigation engineer, Nashville, Tennessee, William Boyd, environmental engineer, Little Rock, Arkansas, Harold Blume, water man- agement engineer, Phoenix, Arizona, Sonia Jacobsen, hydraulic engineer, St. Paul, Minnesota, Don Pitts, water quality specialist, Champaign, Illinois, and Jeffrey Wheaton, conservation engineer, Maite, Guam. The U.S. Department of Agriculture (USDA) prohibits discrimination in all its programs and activities on the basis of race, color, national origin, sex, religion, age, disability, political beliefs, sexual orientation, or marital or family status. (Not all prohibited bases apply to all programs.) Persons with disabilities who require alternative means for communication of program informa- tion (Braille, large print, audiotape, etc.) should contact USDA’s TARGET Center at (202) 720-2600 (voice and TDD). To file a complaint of discrimination, write USDA, Director, Office of Civil Rights, Room 326W, Whitten Building, 14th and Independence Avenue, SW, Washington, DC 20250-9410 or call (202) 720-5964 (voice and TDD). USDA is an equal opportunity provider and employer. (210-VI-NEH, April 2001) Chapter 14 Water Management (Drainage) Contents Subchapter A—General 650.1400 Scope 14–1 (a) Need for soil and water management ........................................................14–1 (b) Natural resource and environmental setting ............................................ 14–3 (c) Factors affecting drainage .......................................................................... 14–3 (d) Benefits related to drainage ........................................................................14–4 (e) Water quality impacts .................................................................................. 14–5 (f) Agriculture drainage setting ........................................................................14–6 (g) Drainage setting for non-agricultural areas .............................................. 14–7 650.1401 Types of drainage systems 14–7 (a) Surface drainage .......................................................................................... 14–7 (b) Subsurface drainage .................................................................................... 14–8 (c) Interception drainage .................................................................................. 14–8 (d) Water table management ............................................................................ 14–8 (e) Drainage pumping ........................................................................................ 14–8 650.1402 Investigations and planning 14–9 (a) Reconnaissance............................................................................................ 14–9 (b) Physical surveys ..........................................................................................14–10 (c) Environmental considerations ..................................................................14–13 (d) Decision matrix .......................................................................................... 14–14 Subchapter B—Surface Drainage 650.1410 General 14–15 (a) Drainage runoff .......................................................................................... 14–15 (b) Determining drainage runoff .................................................................... 14–15 (c) Composite drainage curves ...................................................................... 14–15 650.1411 Investigation and planning of surface drainage systems 14–17 (a) Field ditches ................................................................................................14–17 (b) Types of open drain systems .................................................................... 14–17 (c) Landforming ................................................................................................14–22 (210-VI-NEH, April 2001) 14–i Chapter 14 Water Management (Drainage) Part 650 Engineering Field Handbook 650.1412 Design of open drains 14–24 (a) Drainage runoff .......................................................................................... 14–24 (b) Drain alignment .......................................................................................... 14–25 (c) Hydraulic gradient ......................................................................................14–25 (d) Design methods .......................................................................................... 14–27 650.1413 Construction 14–37 (a) Open drain layout ...................................................................................... 14–37 (b) Structures.................................................................................................... 14–37 (c) Watergates .................................................................................................. 14–37 (d) Surface water inlets ....................................................................................14–37 (e) Berms, spoil banks, and seeding .............................................................. 14–38 (f) Safety ............................................................................................................14–39 650.1414 Maintenance 14–40 (a) Mowing ........................................................................................................ 14–40 (b) Burning ........................................................................................................ 14–41 (c) Chemicals.................................................................................................... 14–41 (d) Biological .................................................................................................... 14–42 (e) Maintenance of land forming ....................................................................14–42 Subchapter C—Subsurface Drainage 650.1420 General 14–45 (a) Plans ............................................................................................................ 14–45 (b) Soils ..............................................................................................................14–45 (c) Economics .................................................................................................. 14–48 (d) Use of local guides ......................................................................................14–48 650.1421 Applications of Subsurface Drainage 14–49 (a) Field drainage ..............................................................................................14–49 (b) Interception drainage ................................................................................ 14–49 (c) Drainage by pumping ................................................................................ 14–49 (d) Mole drainage ..............................................................................................14–49 (e) Water table management .......................................................................... 14–50 (f) Salinity control ............................................................................................14–50 (g) Residential and non-agricultural sites ......................................................14–51 650.1422 Investigations and planning 14–51 (a) Topography ..................................................................................................14–51 (b) Soils ..............................................................................................................14–51