False-color AVHRR satellite image of Columbia River watershed
Characteristics of Columbia River Watershed and Estuary
| Watershed area (km2) | 660,500 |
| Watershed maximum elevation (m) | 3,500 |
| Watershed population (no. individuals) | ~4,000,000 |
| Runoff (1000 m3 d-1) | 600,000 |
| Precipitation (mm d-1) | 1.3 |
| Evaporation (mm d-1) | 0.7 |
| Groundwater flow (1000 m3d-1) | 20,000 |
| Estuary water body area (km2) | 420 |
| Mean depth (m) | 10 |
| Mean tide range (m) | 1.7 |
| Tidal prism (106m3) | 680 |
| Freshwater inflow/tidal prism (flow ratio) | 0.486 |
| Residence time (d) | ~2 |
| Total sediment input (106 MT yr-1) | 10 |
| Mean sedimentation rate (cm yr-1) | 0.5 |
| Range of total suspended solids (mg l-1) | 1-1000 |
| Salinity range (‰) | 0-33 |
| Water temperature range (ºC) | 0-23 |
| Dissolved inorganic phosphorus range (m M) | 0.3-2.2 |
| Nitrate range (m M) | 0.5-40 |
| Ammonium (m M) | 0.3-6.6 |
| Chlorophyll range (m g l-1) | 0.5-20 |
| Net annual primary production (g C m-2yr-1) | 473 |
| Mean primary production by phytoplankton (g C m-2yr-1) | 100 |
| Mean primary production by emergent vascular plants (g C m-2yr-1) | 403 |
| Mean primary production by benthic microalgae (g C m-2yr-1) | 16 |
| Mean secondary production (g C m-2yr-1) | 6 |
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