SOURCES AND FLUX OF NUTRIENTS IN THE MISSISSIPPI RIVER BASIN:
MONITORING, MODELING, & RESEARCH NEEDS
Donald A. Goolsby, U.S. Geological Survey
Monitoring ModelingModeling
ResearchResearch
HISTORICAL NASQAN AND HYDROLOGIC BENCHMARK STATIONS
Source: Alexander, R.B., and others, 1997, USGS Fact Sheet FS-013-97.
NASQAN STATIONS ACTIVE IN 2002
Long-term trends in nitrate concentrations
and flux
42 Interior Basins used in for source/yield estimates in CENR Assessment
CURRENT STATUS (2002) OF NUTRIENT MONITORING IN 42 BASINS IN THE MISSISSIPPI RIVER BASIN
Establish a nutrient monitoring program in the MARB to determine the effects of voluntary actions, changes in nutrient management practices, and new policies aimed at reducing the nutrient flux to the Gulf of Mexico.
Reestablish nutrient monitoring in some of the 42 interior basins used in the CENR assessment. These sites have the benefit of a long period of historical data.
Augment monitoring at this scale by nutrient monitoring in selected small basins, where the effects of changes in nutrient inputs will be most noticeable.
Any monitoring program that is established must include a plan for storage, compilation, timely synthesis and dissemination of data, and periodic reporting of results to all interested parties.
MONITORING NEEDS
Prepared by R. P. Hooper, USGS
USGS (WATER) NUTRIENT MONITORING IN FISCAL YEAR 2001
ATMOSPHERIC DEPOSITION
NADP NITRATE DEPOSITION DATA
NITRATE DEPOSITION BY BASIN
LANDUSE, NITROGEN INPUTS AND OUTPUTS
MONITORING NEEDS CONT.
Continued collection of agricultural statistics like those provided by USDA/NASS
Continued monitoring of nitrogen atmospheric wet deposition (NADP)
Expand efforts to monitor nitrogen (including organic nitrogen) in dry deposition
Establish an effluent monitoring program to improve estimates of nutrient inputs from municipal and industrial sources.
Monitoring
Modeling Research
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652
4
3
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210
TTTT
TTQ
Q
OBSERVED AND PREDICTED NITRATE FLUX TO THE GULF OF MEXICO
Nflux = 0.049Fert2 + 36Q + 0.09Resid1
0
1
2
3
4
5
1950 1960 1970 1980 1990 2000
annualriverine nitrate-N
flux kg N/ha-yr
regression modelobserved flux
12% fertilizer reduction
MODEL: NLM = 0.26*W0.94*e(0.17*NANI2-5+0.08*NANI6-9))
Source: McIsaac, G.F., David, M.B., Gertner, G.Z., and Goolsby, D.A., 2001, Nitrate Flux in the Mississippi River: Nature, v. 14, p. 166-67
OBSERVED AND ESTIMATED NITRATE FLUX IN LOWER MISSISSIPPI RIVER 1955-98
Nitrogen yields of 42 basins (A), nitrogen inputs during 1992 (B), and average annual nitrogen yields of streams for 1980-96 (C)
(kg/km2/yr – kilograms per square kilometer per year
modified from Goolsby and others, 1999
Total N yield (kg/km2/yr) = -95 +
0.39(pctcrop2) + 4.68(popden) + 1.56(no3dep)
2002
Area = 14350 + 0.0263ThebMay-Q + 6360MayNO3_conc +0.0137ThebMayQ-1
MODELING NEEDS
Improve statistical models to provide better estimates of flux at various time scales, sources, trends, etc.)
Watershed and agricultural models to link processes, agricultural practices, hydrology, etc. with nitrogen losses to ground water and streams.
Models to provide feed back for improved design of monitoring programs.
Monitoring Modeling
Research
NITROGEN MASS BALANCE FOR MISSISSIPPI RIVER BASIN
Source: Goolsby and others, 1999, CENR Topic 3 report, figure 6.7
RESEARCH NEEDS
Better understanding of nitrogen dynamics in soils: mineralization, immobilization, leaching, storage, etc.
Research in small watersheds, with and without tile drainage to better understand dynamics and transport of water and nitrogen from fields to streams.
Examine importance of instream processes, such as denitrification in removing nitrogen from streams: effect of stream size and characteristics.
Develop a nitrogen mass balance (inputs and outputs) for the Mississippi basin
Provide feedback for modeling and monitoring efforts
Share results of research, modeling, and monitoring via periodic technical symposia.
QUESTIONS ?
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