TABLE 7.
Estimated Stream Loads and Source Shares of Total Nitrogen Discharged From Six-Digit Hydrologic Unit Code (HUC6) Watersheds in the United States Pacific Northwest (2002 conditions)
| Six-Digit Hydrologic Unit Code (HUC6) Watershed | Estimated Load (metric ton/year) | Share From Primarily Canadian Drainages (%) | Share From Forest Land (%) | Share From Atmospheric Deposition (%) | Share From Farm Fertilizer (%) | Share From Livestock Manure (%) | Share From Point Sources (%) | Share From Developed Land (%) | Share From Alder Trees (%) |
|---|---|---|---|---|---|---|---|---|---|
| Kootenai River (170101) | 2,115 | 66.3 | 24.7 | 3.7 | 2.0 | 1.7 | 0.8 | 0.9 | 0.0 |
| Pend Oreille River (170102) | 2,166 | 2.0 | 55.4 | 9.0 | 4.9 | 13.9 | 11.5 | 3.3 | 0.0 |
| Spokane River (170103) | 5,452 | 0.0 | 28.0 | 4.9 | 8.5 | 5.8 | 40.8 | 11.9 | 0.0 |
| Yakima River (170300) | 3,205 | 0.0 | 12.5 | 5.0 | 26.1 | 43.5 | 5.2 | 7.7 | 0.0 |
| Snake River Headwaters (170401) | 1,326 | 0.0 | 65.3 | 15.3 | 6.0 | 11.9 | 0.8 | 0.7 | 0.0 |
| Upper Snake River (170402) | 7,747 | 0.0 | 1.5 | 1.8 | 19.4 | 36.9 | 38.9 | 1.5 | 0.0 |
| Middle Snake-Boise Rivers (170501) | 19,145 | 0.0 | 4.2 | 2.0 | 20.7 | 40.3 | 30.6 | 2.3 | 0.0 |
| Middle Snake-Powder Rivers (170502) | 23,324 | 0.0 | 6.7 | 2.2 | 19.8 | 40.8 | 28.3 | 2.2 | 0.0 |
| Salmon River (170602) | 2,741 | 0.0 | 72.6 | 9.3 | 2.2 | 12.9 | 2.3 | 0.7 | 0.0 |
| Clearwater River (170603) | 4,218 | 0.0 | 57.0 | 8.3 | 16.4 | 5.9 | 11.3 | 1.1 | 0.0 |
| Lower Snake River (170601) | 21,314 | 0.0 | 22.0 | 4.1 | 20.2 | 31.0 | 20.7 | 2.0 | 0.0 |
| Upper Columbia River (170200) | 82,592 | 1.8 | 21.7 | 4.8 | 21.5 | 26.9 | 19.5 | 3.9 | 0.0 |
| John Day River (170702) | 851 | 0.0 | 61.2 | 8.3 | 7.2 | 23.0 | 0.0 | 0.3 | 0.0 |
| Deschutes River (170703) | 1,945 | 0.0 | 44.7 | 9.1 | 20.7 | 21.2 | 0.0 | 4.3 | 0.0 |
| Middle Columbia River (170701) | 91,490 | 1.5 | 24.0 | 5.2 | 22.1 | 25.5 | 17.3 | 4.1 | 0.3 |
| Willamette River (170900) | 25,243 | 0.0 | 12.9 | 2.8 | 27.2 | 10.9 | 30.0 | 9.3 | 6.8 |
| Lower Columbia River (170800) | 97,507 | 0.7 | 18.9 | 4.4 | 19.7 | 17.2 | 26.0 | 6.5 | 6.4 |
| Puget Sound (171100) | 30,685 | 0.6 | 13.9 | 4.0 | 2.9 | 10.9 | 36.1 | 16.8 | 14.8 |
| Washington Coastal Rivers (171001) | 13,932 | 0.0 | 34.3 | 6.1 | 2.5 | 9.5 | 5.1 | 5.5 | 37.0 |
| Northern Oregon Coastal Rivers (171002) | 13,719 | 0.0 | 23.5 | 4.6 | 1.5 | 11.0 | 1.2 | 2.7 | 55.5 |
| Southern Oregon Coastal Rivers (171003) | 12,452 | 0.0 | 39.3 | 4.1 | 4.2 | 14.1 | 8.4 | 4.7 | 25.3 |
| Oregon Closed Basins (171200) | na | na | na | na | na | na | na | na | na |
Notes: Source shares represent contributions from all upstream sources; na, not applicable because there is no surface water outlet from the watershed.