Appendix A

Model Estimated Nitrogen,
Phosphorus, and Sediment Loads
by Sector for Five Scenarios

TABLE A-1 Total Nitrogen Loads by Source (million pounds per year)

Source 1985 2009 TS TMDL E3
Agriculture 161.8 109.4 71.5 69.4 54.0
Urban runoff 21.0 20.4 15.7 15.6 7.7
Point source 90.9 53.2 44.3 39.1 23.7
Septic 8.2 11.0 7.4 8.4 4.6
Forest 55.9 49.3 50.8 50.9 48.3
NTW atm. deposition 4.1 2.5 2.6 2.6 2.3
All Sources 341.9 245.8 192.3 186.0 140.6
 

TABLE A-2 Total Phosphorus Loads by Source (million pounds per year)

Source 1985     2009 TS      TMDL         E3
Agriculture 9.2 7.3 5.5 5.1 4.4
Urban runoff 2.3 2.4 1.9 1.7 0.6
Point source 10.1 4.2 4.2 3.1 1.0
Septic 0.0 0.0 0.0 0.0 0.0
Forest 2.3 2.4 2.5 2.5 2.5
NTW atm. deposition 0.1 0.2 0.2 0.2 0.2
All Sources 24.0 16.5 14.3 12.6 8.7
 


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Appendix A Model Estimated Nitrogen, Phosphorus, and Sediment Loads by Sector for Five Scenarios TABLE A-1 Total Nitrogen Loads by Source (million pounds per year) Source 1985 2009 TS TMDL E3 Agriculture 161.8 109.4 71.5 69.4 54.0 Urban runoff 21.0 20.4 15.7 15.6 7.7 Point source 90.9 53.2 44.3 39.1 23.7 Septic 8.2 11.0 7.4 8.4 4.6 Forest 55.9 49.3 50.8 50.9 48.3 NTW atm. deposition 4.1 2.5 2.6 2.6 2.3 All Sources 341.9 245.8 192.3 186.0 140.6 TABLE A-2 Total Phosphorus Loads by Source (million pounds per year) Source 1985 2009 TS TMDL E3 Agriculture 9.2 7.3 5.5 5.1 4.4 Urban runoff 2.3 2.4 1.9 1.7 0.6 Point source 10.1 4.2 4.2 3.1 1.0 Septic 0.0 0.0 0.0 0.0 0.0 Forest 2.3 2.4 2.5 2.5 2.5 NTW atm. deposition 0.1 0.2 0.2 0.2 0.2 All Sources 24.0 16.5 14.3 12.6 8.7 185

OCR for page 185
186 NUTRIENT AND SEDIMENT REDUCTION GOALS IN THE CHESAPEAKE BAY TABLE A-3 Total Sediment Loads by Source (million pounds per year) E3 Source 1985 2009 TS TMDL Agriculture 6,830 5,240 3,794 3,887 3,441 Urban runoff 1,234 1,283 1,067 798 131 Point source 144 71 29 229 32 Septic 0 0 0 0 0 Forest 1,435 1,495 1,577 1,539 1,501 NTW atm. deposition 0 0 0 0 0 All Sources 9,643 8,089 6,467 6,453 5,105 NOTES: Loads are as delivered to the Chesapeake Bay under five simulations of the Phase 5.3 watershed model. The scenarios are modeled using the same hydrologic conditions (1985- 2005) and changing land use, point source, and BMP conditions. The scenarios include 1985 baseline conditions, 2009 progress, the tributary strategy (TS) goals based on the cap loads set in 2003, total maximum daily load (TMDL), and maximum feasible reduction (E3) scenarios. The E3 scenario is a “what if” scenario of watershed conditions with theoretical maximum levels of managed controls on load sources (“everything, by everyone, everywhere”), with no cost and few physical limitations to implementing BMPs for point and nonpoint sources. Source sectors include agriculture, urban runoff, point sources (including wastewater), septic systems, forested lands, and non-tidal waters atmospheric deposition (NTW Dep). Note that in these simulations, atmospheric deposition is considered separately only when it falls directly on non-tidal waters, and otherwise, the source is attributed to the land-use type on which the deposition falls. SOURCE: S. Ravi, CBPO, personal communication, 2011.