Table 1.
Summary of key model drivers for year 2002 and two 2022 scenarios for the total Mississippi River Basis (MRB)
| Model drivers | 2002HIST | 2022BASE | 2022CROP | Sources |
|---|---|---|---|---|
| Agriculture | ||||
| Land management | ca. 2002, all conservation tillage | Intensification, conservation tillage | 2022BASE plus extensification | Elobeid et al. (2013); EPIC simulation |
| Corn ethanol production, billion gallon ethanol |
Corn Grain: 0 Corn Stover: 0 |
Corn Grain: 12.3 Corn Stover: 0 |
Corn Grain: 18.4 Corn Stover: 10.7 |
2022BASE: https://www.gpo.gov/fdsys/pkg/FR-2010-03-26/pdf/2010-3851.pdf, Table IV.A.2-1 2022CROP: Elobeid et al. (2013) |
| Organic and inorganic fertilizer (TNfert) (kg N km−2 year−1) | 3285 | 3578 | 3513 | EPIC simulation |
| Crop BNF (TNBNFcrop), (kg N km−2 year−1) | 1715 | 1753 | 1744 | EPIC simulation |
| Atmospheric CO2, ppm | 372 | 412 | 412 | http://www.esrl.noaa.gov/gmd/ccgg/trends |
| Basin area where tile drains are present (%) | 8 | 8 | 8 | Sugg (2007) |
| Atmospheric N deposition | ||||
| Atmospheric N deposition (TNdep) (kg N km−2 year−1) | 905 | 707 | 707 | CMAQ simulation |
| Human sewage | ||||
| TN in human excrement (TNsew), kg N person−1 year−1 | 6.1 | 6.1 | 6.1 | Sobota et al. (2013) |
| Population (million people) | 69.7 | 84.2 | 84.2 | US Census (2014) |
| Population connected to municipal sewage systems (%) | 69 | 70 | 70 | USEPA (2008) |
| TN exported from WWTP as DIN (FEsew) (%) | 45 | 41 | 41 | USEPA (2008), Van Drecht et al. (2009) |
Values for sub-basins may differ from those used for the MRB (see also Supplemental Fig. S1)