technology slides for hypoxia case study sts

8/7/2019 technology slides for hypoxia case study STS

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Hypoxia Case Study:

Engineering solutions


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Agricultural Drainage

the use of surface ditches, subsurface

permeable pipes, or both, to remove standing

or excess water from poorly drained lands.


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Why drain?

Usually increase crop yields on poorly drained

soils by providing a better environment for

plants to grow, especially in wet years.

Help improve field conditions for timely

tillage, planting and harvesting.

These two factors have improved agricultural

production on nearly one-fifth of U.S. soils1.


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Adverse impacts of drainage

hydrology of watersheds

the water quality of receiving water bodies

the amount and quality of nearby wetlands


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HEATHWAITE,A. L. and JOHNES, P. J. (1996), CONTRIBUTION OF NITROGEN SPECIES

AND PHOSPHORUS FRACTIONS TO STREAMWATER QUALITY IN AGRICULTURAL

CATCHMENTS. Hydrological Processes, 10: 971983.


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Challenges associated with agricultural

drainage

Hydrology

Water Quality

Wetlands


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Hydrology

Anecdotal evidence suggests that streams and

ditches have become flashier over time

(Of course, more significant impact wh

enconverting the land to agricultural)

Reduces surface runoff by 29-45%

Increases base flow to streams


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Water Quality

Increase loss of nutrients and sediments that

occur with surface runoff

Decreased surface runoff can reduce sedimentlosses by 16-65% and P losses by ~45%

Main concern is the increased loss of nitrates


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Wetlands

Loss of wetland ecosystems, valued for water

storage and increasingly for their role to

improve water quality, is likely driven by

agricultural and urban drainage activities

More on this in a bit


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Agricultural Drainage

1800s, European settlers made drainage

ditches and channelized stream

Later, increased drainage by installingsubsurface drainage pipes at 3-6 ft depth

Until 1970s, made from short, cylindrical

sections of concrete or clay called tile

Today, perforated plastic tubing is used


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What does t

his ch

ange in tech

nologymean for hypoxia in the Gulf?


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Systems view of technology change


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Outcome of LCA


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LCA of concrete


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LCA of plastic


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Concrete vs. Plastic


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Returning to Gulf: Improved drainage

system design

It has been proposed that placing drainage pipesat shallower depths might result in less nitrateloss.

This would happen because nitrate would bemore likely to reach a biologically active butsaturated zone and be converted to nitrogen gasby denitrifying bacteria.

The conversion of nitrate/nitrogen to nitrogen gaswould prevent the nitrate from reaching thedrainage pipes and nearby surface waters.


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Controlled drainage

BMP for mitigating nitrate losses from

drainage systems

Water control to raise water elevationdecreasing the depth of the drained field

Decreases volume of water drained by 15-35%

and significantly decreases nitrate losses (up

to 50%)


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Drainage systems


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Skaggs, R.W. , Brev, M. A. and Gilliam, J. W.(1994) 'Hydrologic and water quality

impacts of agricultural drainage*', Critical Reviews in Environmental Science and

Technology, 24: 1, 1 32


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Freshwater wetlands

Means of treating water from drainage system

Biological activity in wetlands can be effective

at removing nitrate by converting it to N2 Wetlands can remove 20-80% of annual

nitrate subsurface drainage water

Timing of peak activity, excess runoff, season?


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Effectiveness of Restored Wetlands for the Treatment of Agricultural

Runoff; EPA 600/R-08/055 | January 2008 | www.epa.gov/ada


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Effectiveness of Restored Wetlands

for the Treatment of Agricultural

Runoff; EPA 600/R-08/055 |

January 2008 | www.epa.gov/ada


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Effectiveness of Restored

Wetlands for the Treatment ofAgricultural Runoff; EPA 600/R-

08/055 | January 2008 |

www.epa.gov/ada


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EPA 600/R-08/055 | January 2008 |

www.epa.gov/ada




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Jose A. Romero, Francisco A. Comn, Carmen Garca; Restored wetlands as

filters to remove nitrogen; Chemosphere, Volume 39, Issue 2, July 1999, Pages

323-332


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Wetland variables

Date restored

Area

% cropland in watershed Watershed:wetland ratio


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Not just N (and P)

What else do we need to worry about in

drainage water reaching receiving waters?


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M. T. Moore, J. H. RodgersJr., S. SmithJr., C. M. Cooper; Mitigation of metolachlor-

associated agricultural runoff using constructed wetlands in Mississippi, USA;

Agriculture, Ecosystems & Environment, Volume 84, Issue 2, April 2001, Pages 169-176


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M. T. Moore, J. H. RodgersJr., S. SmithJr., C. M. Cooper; Mitigation of metolachlor-

associated agricultural runoff using constructed wetlands in Mississippi, USA;

Agriculture, Ecosystems & Environment, Volume 84, Issue 2, April 2001, Pages 169-176


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Conservation Buffers


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Cropping systems

Row crops such as corn and soybeans

experience considerably more nitrate loss

through subsurface drainage flow than

perennials such as alfalfa and brome grass

Crop rotations


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Animal production systems


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Randall, G., and D.J. Mulla. 2001. "Nitrate Nitrogen in SurfaceWaters as

Influenced by Climatic Conditions and Agricultural Practices." Journal of

Environmental Quality 30: 337-344.


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Actions for other NP sources

Randall, G., and D.J. Mulla. 2001. "Nitrate Nitrogen in SurfaceWaters as

Influenced by Climatic Conditions and Agricultural Practices." Journal of

Environmental Quality 30: 337-344.


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Actions for point sources


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Biofuels - Ethanol

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