TABLE 8.
Estimated Stream Loads and Source Shares of Total Phosphorus 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 Geologic Material (%) | Share From Farm Fertilizer and Livestock Manure (%) | Share From Point Sources (%) | Share From Developed Land (%) |
|---|---|---|---|---|---|---|
| Kootenai River (170101) | 174 | 42.1 | 49.9 | 4.9 | 1.9 | 1.2 |
| Pend Oreille River (170102) | 235 | 0.8 | 75.4 | 11.0 | 10.5 | 2.3 |
| Spokane River (170103) | 186 | 0.0 | 45.9 | 5.9 | 42.6 | 5.6 |
| Yakima River (170300) | 670 | 0.0 | 52.4 | 23.1 | 18.3 | 6.2 |
| Snake River Headwaters (170401) | 299 | 0.0 | 94.1 | 5.5 | 0.1 | 0.3 |
| Upper Snake River (170402) | 718 | 0.0 | 13.0 | 22.7 | 63.5 | 0.7 |
| Middle Snake-Boise Rivers (170501) | 1,242 | 0.0 | 25.3 | 26.3 | 47.2 | 1.2 |
| Middle Snake-Powder Rivers (170502) | 1,785 | 0.0 | 31.7 | 25.5 | 41.7 | 1.2 |
| Salmon River (170602) | 341 | 0.0 | 93.2 | 4.3 | 2.0 | 0.5 |
| Clearwater River (170603) | 375 | 0.0 | 75.2 | 14.0 | 10.3 | 0.5 |
| Lower Snake River (170601) | 1,630 | 0.0 | 51.1 | 20.4 | 27.5 | 1.0 |
| Upper Columbia River (170200) | 3,677 | 0.9 | 52.5 | 18.6 | 26.1 | 2.0 |
| John Day River (170702) | 107 | 0.0 | 91.9 | 7.9 | 0.0 | 0.3 |
| Deschutes River (170703) | 366 | 0.0 | 84.6 | 13.5 | 0.0 | 1.9 |
| Middle Columbia River (170701) | 5,024 | 0.7 | 55.4 | 16.9 | 24.7 | 2.4 |
| Willamette River (170900) | 2,438 | 0.0 | 45.2 | 19.7 | 27.5 | 7.5 |
| Lower Columbia River (170800) | 10,272 | 0.3 | 50.0 | 14.5 | 30.5 | 4.6 |
| Puget Sound (171100) | 3,283 | 0.2 | 44.9 | 5.0 | 39.9 | 10.0 |
| Washington Coastal Rivers (171001) | 1,563 | 0.0 | 78.9 | 4.6 | 12.2 | 4.3 |
| Northern Oregon Coastal Rivers (171002) | 880 | 0.0 | 86.9 | 8.2 | 1.4 | 3.4 |
| Southern Oregon Coastal Rivers (171003) | 1,470 | 0.0 | 80.3 | 9.0 | 7.4 | 3.4 |
| Oregon Closed Basins (171200) | 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.