Table 2.
Budget of N transfers along the cascade from agricultural soils to the river outlet in a number of regional watersheds. Data from [7–10]; see electronic supplementary material, §S5 for a graphical representation of the same data. n.a., not available.
| watershed year | Seine 2006 | Scheldt 2005 | Ebro 2000 | Mississippi 1996 | Hong 1997 |
|---|---|---|---|---|---|
| watershed area (km²) | 92 000 | 19 860 | 84 979 | 3200 | 156 450 |
| agricultural surplus (kg N km−² yr−1) | 4200 | 6915 | 3890 | 600 | 1745 |
| root-zone processes | n.a. | 400 | n.a. | n.a. | n.a. |
| groundwater storage | 700 | 400 | n.a. | n.a. | n.a. |
| riparian denitrification | 1160 | 1200 | n.a. | n.a. | 810 |
| gross urban point sources | 1285 | 3480 | 292 | 130 | 1030 |
| wastewater treatment or recycling | 735 | 2430 | 118 | 40 | 530 |
| net point sources release into rivers | 550 | 1050 | 174 | 90 | 500 |
| benthic denitrification and sedimentation | 210 | 250 | n.a. | n.a. | 250 |
| river export to the sea | 2680 | 2500 | 394 | 396 | 1100 |