TABLE A-3 Total Sediment Loads by Source (million pounds per year)

Source 1985 2009 TS TMDL E3
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.

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