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Using Wetland Restoration to Achieve Improvements Down River Wetland Restoration in the Mississippi River Basin and the Gulf Hypoxia William J. Mitsch, Ph.D. The Ohio State University
Key Citations Mitsch, William J. , John W. Day, Jr., J. Wendell Gilliam, Peter M. Groffman, Donald L. Hey, Gyles W. Randall, and Naiming Wang. 2001. Reducing nitrogen loading to the Gulf of Mexico from the Mississippi River Basin: Strategies to counter a persistent ecological problem. BioScience 51: 373-388. Mitsch, W.J., J.W. Day, Jr., J.W. Gilliam, P.M. Groffman, D.L. Hey, G.W. Randall, and N. Wang. 1999. Reducing nutrient loads, especially nitrate-nitrogen, to surface water, groundwater, and the Gulf of Mexico. Topic 5 Report for the Integrated Assessment on Hypoxia in the Gulf of Mexico. NOAA Coastal Ocean Program Decision Analysis Series No. 19. NOAA Coastal Ocean Program, Silver Spring, MD, 111 pp.
3,000,000 km2 15,000 km2
Final RecommendationsSolving the Gulf of Mexico Hypoxia 1. Several on-farm practices should be implemented including a 20% reduction in nitrogen fertilizer application due primarily to proper nitrogen crediting and the use of realistic yield goals. (Other practices include optimum timing of fertilizer application, use of alternative crops, wider spacing of subsurface drains, and better management of livestock manures.)
Final RecommendationsSolving the Gulf of Mexico Hypoxia • A major effort to restore or create 5 million acres [2 million ha] of wetlands and 19 million acres [7.7 million ha] of riparian forest or some other combination of these two approaches should be undertaken in the Mississippi River Basin. 3. Wetland and riparian zone restoration should be strategic to optimize nitrogen retention/loss.
Final RecommendationsSolving the Gulf of Mexico Hypoxia 8. Any nitrogen mitigation efforts should be coupled to a comprehensive program of monitoring, research, and modeling.
Landscape-scale recommendations Better Fertilizer Management Created/Restored Wetlands (2 million ha) Restore Riparian Bottomlands (7.7 million ha)
Land Drainage in USA Mississippi River Watershed 1 DOT = 8000 hectares
Research RecommendationsMitsch et al. 1999 hypoxia report AGRONOMIC 1. More refined soil nitrogen testing procedures need to be developed and tested. 2. The newly developing concept of “precision farming” needs to be investigated thoroughly for its ability to reduce nitrate losses from an agricultural landscape. 3. Alternatives to the traditional corn-soybean rotation and their effects on nitrate loss to subsurface drainage water should be investigated. 4. The effects of variables such as drainage tile spacing and depth and the effectiveness of controlled drainage on nitrogen retention in poorly drained soils need to be determined through controlled experiments.
Research RecommendationsMitsch et al. 1999 hypoxia report ECOLOGICAL 5. There is a critical need to better understanding of nitrogen behavior during floods and catastrophic events, particularly in ecotechnological methods for nitrate-nitrogen control such as riparian zones and other wetlands. 6. Controlled large-scale experiments on the fate of nitrogen are needed on the reflooding of formerly tile-drained lands as restored wetlands. 7. Research is needed on the long-term efficacy of wetlands for denitrification, including the time required for organic carbon accumulation in created wetlands and the role that this accumulation has on denitrification. 8. There is a critical need for additional farm-scale studies on integration of crop land, riparian buffers, and wetlands to most effectively reduce nitrogen entry into streams.
Research RecommendationsMitsch et al. 1999 hypoxia report 9. There should be a comprehensive effort to determine the mix of different nitrate reduction strategies which give the best nitrate reduction for the least cost. This effort should involve pilot studies in different parts of the Mississippi River Basin. 10. Additional study and modeling is needed to demonstrate the relationships among land subsidence, river diversion rates, and nitrogen uptake in the delta region of Louisiana. 11. A complete accounting of the production of the greenhouse gas N2O from both increased wetland development as well as from drained and fertilized agricultural land is needed in comparative studies. 12. Studies are needed on projected increases in population and other development in the Mississippi River Basin and on how these changes might offset reductions in nitrogen loadings from the basin.
Ecological Research and Monitoring Approach (Recommendations 5 - 12) • Several year’s of continued monitoring and research of wetland sites already established in basin and deltaic diversions. • Development of additional comprehensive full-scale demonstration and experimental wetlands throughout the Mississippi River Basin to broaden the data base.
WETLAND SITES ARE ALREADY ESTABLISHED IN SOME CASES A combination of research on wetlands and wetland processes at several scales……. Olentangy River Wetland Research Park Columbus, Ohio, USA
Nutrient Removal by experimental wetlands, 1994-99 Wetland 1 (planted) Wetland 2 (naturally colonized) 1996 1993 1994 1995 1997 1998 1999 0 Total P -20 -40 -60 Percent Change -20 SRP * -40 -60 -80 NO + NO -20 3 * 2 -40 * Significantly different (a = 0.05) -60
Demonstration wetlands (5 - 50 ha) upstream well downstream well 221.5 Restored bottomland forest 221.3 221.1 ground surface 220.9 220.7 220.5 Created oxbow 221.3 water level 221.1 m above MSL 220.9 220.7 ground surface 2.5 ha 2 2 1 . 9 2 2 1 . 5 O l e n t a n g y R i v e r s t a g e 2 2 1 . 3 2 2 1 . 1 2 2 0 . 9 2 2 0 . 7 2 2 0 . 5 J F M A M J J A S O N D 2 0 0 1
Water quality changes through created oxbow during flood events, 1999-2001 (ave ± std error (# samples)) * Manual sampling; ** auto-sampling Mitsch and Zhang, 2002
Freshwater Diversions in the Delta Region (> 100 ha)
Nitrogen Decrease in Mississippi Diversion Structure m3 s-1 NO3 (umol L-1) TN(umol L-1) Salinity
50 NO3 –N removal 30 (g–N m-2 yr-1) Y = 1.81•X 0.62 10 r2 = 0.75 100 annual data Y = -0.43•Log(X) + 1.22 r2 = 0.57 regression line % NO3 –N removal 60 95% CI (by mass) 20 100 Y = -0.45•Log(X) + 1.23 r2 = 0.84 % NO3 –N removal 60 (by concentration) 20 40 120 0 80 160 200 Inflow of Nitrate (g–N m-2 yr-1) Example of empirical models to extend experimental and demonstration wetlands to a larger scale
Sample location of experimental and demonstration wetlands in the basin UPPER MISSOURI MISSISSIPPI LOWER OHIO MISSISSIPPI wetland research station Gulf of Mexico Hypoxia
A Comprehensive Research Program Design Using Wetland Creation, Riparian Restoration, and River Diversion for Reducing Nitrogen Loading to the Gulf of Mexico 5-year research program • $ million • Experimental wetlands (10 sites; 1-10 ha ea) 9 • Land purchase/rental 3 • Basin wetland/riparian research initiatives 8 • River diversion research (5 sites) 5 • Modeling (ecosystem and watershed scale) 2 • ______ • TOTAL 27