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“Stages” of DrainageNative prairie grasses, wet landscape, high evaporation and transpiration rates
(late 1800’s – 1920’s) Conversion to agriculture w/ early drainage, targeted ditching,
Continued ditching, targeted tiling, surface inlets in depressions, more intensive row cropping
(late 60’s – early 70’s) Advent of plastics, drain plows, large pattern drainage projects, fewer crops in rotation
(current) replacement of old tile, intensification on previously drained fields
The Impacts of Tile Drainage . . .With Artificial Drainage
Increased nitrate-nitrogen lossesLower peak flows, higher sustained low flowsFewer temporary wetlands
N has about 9.5 million acres remaining (~50%)
Aging and repair of undersized infrastructureProductive ag lands benefit local and state levels
Without Artificial DrainageIncreased sediment & phosphorus lossesHigher peak flows, more localized floodingMore temp wetlands
Increased habitat
Depend on natural drainage-ways only“Income” derived from other ecological services
Water Quality Concern (Nitrogen)
Drinking Water
Quality
Hypoxia in the Gulf of Mexico
Cost of N Losses
Hypoxia/Anoxia of Coastal SystemsHypoxia (low oxygen) in coastal ecosystems is impetus behind research
Systems very complex
Coastal systemsnitrogen limiting
Upper Midwestresponsible formuch nitrate
Recent concernover role of P
Nitrogen by Drainage Basin
2002 estimated nitrate/nitrite loading:
960,000 metric tons(12th highest in 22 yrs)
Loss of WetlandsSociety placing higher value
Drainage increasingly associated with loss of wetlands States with notable wetland loss (1860-1900)
Swamp land act acres granted
New Drainage “Mantra”
Drain only that which is necessary to ensure
trafficability and crop production …
—and not a drop more!
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