Transcript Engineering Field Tools

Agricultural Drainage Systems
Hamid J. Farahani, Ph.D.
Water Management Engineer
USDA-NRCS East NTSC
Greensboro, North Carolina
Deena Wheby
MRBI Coordinator
(859) 224-7403
[email protected]
USDA is an Equal Opportunity Employer & Provider
Subsurface drainage systems
• Drainage has been around in America since 1700’s
• Controlled drainage was initiated in 1930’s
Subsurface drainage via open ditch
Lower Mississippi, Coastal areas, NC,
and many places worldwide
Online Drainage Advisory - NCSU
Subsurface drainage via drain pipe
Midwest, West (salinity), and many
places worldwide
University of Minnesota Extension, 2002
Open
Field
Ditches
Surface Drainage
Drainage Ditch
(Lynn Betts, Iowa)
Drainage
Ditch
Surface Drainage
Impermeable Layer
Surface Drainage
Water Table
Drainage
Ditch
Subsurface Flow
Courtesy of Dr. Timothy Appelboom, NCSU, Raleigh; Aug 2011
Subsurface Drainage
via Drain (pipe)
Mole drain
Tile drain (clay & concrete)
Perforated plastic drain
Univ. of Minnesota Extension Publication – Issues & Answers, 2002
Benefits of drainage
Drained land = 25%




Enhanced trafficability
Warmer, drier soils
at spring planting
Protection from excessive
soil-water conditions
Improved yield
Drawbacks – Unrestricted flow causing nutrient loading of streams
For instance: Hypoxia in the Gulf of Mexico is attributed to
nutrients drained from lands in the Midwest.
From Disposal to Management
Problem:
Unrestricted drainage provides no
control on discharge volume
and/or timing
Solution:
Controlled drainage
(DWM-Practice Standard 554)
Basic Practice in DWM is: Hold water back, except at planting and harvest.
Manipulate Water Table via Controlled Flow and Timing
Water
Table
From Dr. Larry Brown, OSU Extension; originally from D. Pitts, NRCS, IL
Research suggest:
40% reduction in outflow
40-60% reduction in N
Where does the water go?
Increased ET
Increased leaching???
Potential for increased runoff
Increased soil storage
Drainage Volume without DWM
Is DWM effective?
Where does the N go?
Decreased flow
Increased denitrification
Increased time for crop uptake
Drainage Volume with DWM
Dr. Gary Sands, Presentation at ADMC Drainage workshop, 2011
DWM is Only a Part Solution
Employ DWM with Other Practices in a Systems Approach to
Environmental and Economic Sustainability
Complementing conservation and conservation drainage practices:
•
•
•
•
•
•
•
•
Nutrient BMP's
Bioreactors
Two-stage/managed ditches
Buffers
Improved drainage design (precision drainage)
Improved surface & side inlets
Winter cover crops
Water storage/Nutrient retention basins
Next Presentation
Ruth Book