Table 4.
Uncalculated 5th centile hazardous concentrations (XCD05) because there were <20 samples to estimate the 25th centile background specific conductivity (μS/cm). Ecoregion 76, the Everglades, is a unique system and is influenced by saltwater intrusion.
| Source of data | ||||
|---|---|---|---|---|
| EPA-survey | Modeled | |||
| Level III ecoregion number and name | N | SC Range | Mean base-flow SC | |
| 2 | Puget Lowland | 11 | (50–228) | 71 |
| 5 | Sierra Nevadaa | 18 | (19.1–207) | 144 |
| 12 | Snake River Plaina | 4 | (136–582) | 300 |
| 14 | Mojave Basin and Rangea | 2 | (2860) | 503 |
| 22 | Arizona/New Mexico Plateaua | 10 | (76.9–533) | 486 |
| 24 | Chihuahuan Desertsa | 1 | (3500) | 504 |
| 28 | Flint Hills | 18 | (350–800) | 472 |
| 30 | Edwards Plateau | 6 | (372–693) | 489 |
| 31 | Southern Texas Plainsa | - | - | 462 |
| 32 | Texas Blackland Prairiesa | 5 | (143–849) | 321 |
| 33 | East Central Texas Plainsa | 6 | (188–1560) | 254 |
| 34 | Western Gulf Coastal Plain | 16 | (71–2046) | 203 |
| 41 | Canadian Rockies | 7 | (117–364) | 138 |
| 46 | Northern Glaciated Plains | 21 | (451–2890) | 329 |
| 48 | Lake Agassiz Plain Range | 13 | (618–2630) | 341 |
| 49 | Northern Minnesota Wetlands | 8 | (77.3–607) | 256 |
| 53 | Southeastern Wisconsin Till Plains Range | 9 | (227–1070) | 388 |
| 56 | Southern Michigan/Northern Indiana Drift Plains | 19 | (295–1140) | 246 |
| 57 | Huron/Erie Lake Plains | 8 | (336–1980) | 307 |
| 76 | Southern Florida Coastal Plainb | 603 | (1.2–4540) | 183 |
| 79 | Madrean Archipelagoa | - | - | 401 |
| 81 | Sonoran Basin and Rangea | 5 | (279–12300) | 495 |
| 85 | Southern California/Northern Baja Coasta | 12 | (368–4100) | 566 |
a
Predicted mean base-flow varies by more than 200 μS/cm in 20% stream segments in ecoregion.
b
Unique system, Everglades