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Biological Systems Engineering
Agricultural Drainage, Extreme Weather,
and Management Opportunities
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Outline
Why do we need agricultural drainage in VA?
What are the approaches to drainage & water table
management?
How does extreme weather drive need for drainage?
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Benefits
Artificial drainage…
• Increases land productivity
• Improves trafficability and
timeliness
• Provides opportunity to
control & treat discharges
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Benefits
Artificial drainage…
• Increases land productivity
• Improves trafficability and
timeliness
• Provides opportunity to
control & treat discharges
Watershed Science and Engineering Group
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Benefits
Artificial drainage…
• Increases land productivity
• Improves trafficability and
timeliness
• Provides opportunity to
control & treat discharges
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\
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What are the approaches to drainage
& water table management?
• Different practices for different conditions
• Source of water
• Surface, subsurface, combination strategies
• Drainage vs. water table control
• Drainage only or water table control
• More opportunity to improve water quality
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Ag Drainage 101
Surface drainage problems
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Ag Drainage 101
Subsurface drainage problems
Does not remove plant available water
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Ag Drainage 101: Approaches
Problem & Soil Characteristics
Soil completely saturated
(poorly drained)
Potential Solution
Ditch or tile
Low infiltration rate
(clay or compacted soils)
Surface
smoothing
Shallow impeding soil layers
Ditches or tile
with inlets
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Ag Drainage 101: Surface
Ditching
• Fine textured soil,
low permeability
• Water originating onsite
Land Leveling
(Source: bae.ncsu.edu)
(gpsontario.ca)
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Two-stage Channel
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Ag Drainage 101: Subsurface
Removes water from the root zone
(Source: G. Sands, UMN)
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Ag Drainage 101: Subsurface - Plans
Different configurations:
Different spacing requirements:
(omafra.gov.on.ca)
(extension.iastate.edu)
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Ag Drainage 101: Combined Systems
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Environmental Consequences
• Water quantity manipulation
• Water quality alteration
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Ag Drainage 101: Managed Systems
• Environmental
benefits
• Conservation
Practice
Standard 554
• More efficient
use of rainfall,
decreased need
for irrigation
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Ag Drainage 101: Managed Systems
Drainage Handbook
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How does extreme weather drive need for drainage?
Need for drainage water management is site
specific:
•
•
•
•
•
•
Climate
Geology
Topography
Soil characteristics
Crops
Farming methods
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…and the
climate is
changing!
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Precipitation Trends in Virginia:
• Eastern VA: 13-29%
Rainfall
generally
increasing
1980-2014
• Western VA: 10-22%
• North central VA: -3-7%
• South-central VA: -2-8%
100
75
70
Eastern VA
90
y = 0.2888x - 528.13
R² = 0.08737
65
y = 0.1898x - 343.45
R² = 0.00938
70
Precipita on (in)
55
50
45
60
50
40
30
40
20
35
30
1975
Western VA
80
60
Precip (in)
Rainfall
intensity
increasing
as well
10
1980
1985
1990
1995
2000
2005
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2010
2015
0
1975
1980
1985
1990
1995
2000
2005
2010
2015
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Future Precipitation Trends?
Predicted 2041-2070 precipitation changes
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Water quality implications of
extreme weather
• Increased nutrient and sediment export
• Increased soil erosion
• Increased demand on water supply
drive need for controlled drainage
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‘The question then is not whether one can afford to drain, but
whether one can afford not to drain’
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Contact
Zachary Easton
Assistant Professor
zeaston@vt.edu
540-231-0689
Emily Bock
Grad Research Assist.
emilyml@vt.edu
757-710-1503
http://www.virginiaplaces.org/waste/stormwater.html
Thank you!
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Resources
• National Engineering Handbook – USDANRCS
• Ch 10, part 634-Drainage, Water Table Control
• Ch 14, part 650-Water Management, Drainage
• Extension publication:
• extension.umn.edu/agriculture
• For Virginia—coming soon!
• Agricultural Drainage Management Stems
Task Force
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List of Drainage BMPs
• General:
• controlled drainage
• Ditch systems:
• Tile systems:
• Reactive barriers
• Reduced dip out
frequency mowing
• Biofilters
•
Two-stage
ditches
• Wetlands (surface,
• Reactive barriers,
riparian)
in-ditch filters
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