It is the MIX of physical, biological and chemical variables that influence stream characteristics--that makes them similar within their area, or at a particular stage of a stream or river, and different from other areas or river stages.
| PARAMETER | HEADWATERS | MEDIUM-SIZED STREAMS | LARGE RIVERS |
|---|---|---|---|
| Temperature | cool | warmer | surface: warm bottom: cool |
| Dissolved Oxygen | high: turbulence causes oxygenation | can be lowered by warmer temperatures | moderate: varies directly with the amount of sunlight because aquatic plants produce oxygen in the daytime. |
| BOD (How much oxygen has been used up?) |
low | moderate | can be high, especially in deep or slow rivers where lots of organic material decomposes--smells like sulphur. |
| pH <5=too acidic >8=too alkaline Organisms need pH = 5-8 |
neutral to alkaline | slightly acidic to slightly alkaline | acidic to neutral |
| Turbidity (How clearly can light pass through the water column?) |
Usually low, but streams in the Western Cascades can be tea-colored (from acids from decaying leaf matter.) | moderate: directly influenced by higher flow, which brings particles into the water column. | high: especially after storms and during the high-flow season. |
| Total Solids (What solids make the water turbid?) |
low: follows flow volumes | moderate | can be high |
| Total Phosphorus | very low | low-moderate | highest: increasing breakdown of organic material |
| Nitrates | low | higher: due to greater water surface area | highest: increasing breakdown of organic material |
| Fecal Coliform Bacteria | very low | low: any fecals probably caused by warm-blooded animals | moderate: cumulative as you go downstream |