CADDIS Volume 2: Sources, Stressors & Responses
Temperature
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Authors: K.G. Sappington, S.B. Norton
Adapted from Moore et al. (2005) and Johnson and Jones (2000).
Temperature is the concentration of thermal energy in a substance such as water. The phrase “thermal regime“ is used when emphasizing the temporal and spatial distribution of temperature. Temperatures in streams and rivers are influenced by many atmospheric and hydrologic processes that influence the movement of heat (Figure 1). In turn, temperature plays a fundamental role in shaping the structure and function of aquatic systems (Table 1), and is frequently used as a basis for classifying streams (e.g., cold-water, warm-water).
This module provides advice for deciding whether to include temperature in your list of candidate causes. You may go directly to a specific section of interest by clicking on the tabs above.
| Category | Example attributes |
|---|---|
| Physical | Water density, thermal stratification, solubility of oxygen and other chemicals |
| Chemical | Rates of nutrient cycling, contaminant transformation rates |
| Biological | Organism survival, growth, reproduction, development, behavior, habitat preference, competition |
Checklist of sources, site evidence and biological effects
Temperature should be listed as a candidate cause when potential or observed human source and activities, site observations, or observed effects support portions of the source-to-impairment pathways in the conceptual model for temperature (Figure 2). The more the thermal regime departs from the natural regime, the more likely it is to cause undesirable biological effects. Although increased temperature is most frequently thought of as the stressor of concern, undesirable effects also can be associated with decreases in temperature, increases in temperature ranges, and increased rates of temperature change.
The checklist below will help you identify key data and information useful for determining whether to include temperature among your candidate causes. The list is intended to guide you in collecting evidence to support, weaken, or eliminate temperature alteration as a candidate cause. For more information on specific sources and activities, site evidence, and biological effects listed in the checklist, click on checklist headings or go to the When to List tab of this module.
Consider listing temperature as a candidate cause when the following sources and activities, site evidence, and biological effects are present:
Sources and Activities
- Discharge of heated effluents
- Removal of riparian vegetation
- Removal of upland vegetation
- Impervious surfaces
- Channel alteration
- Impoundments or dams
- Removal of water from surface or groundwater
Site Evidence
- Reduced riparian cover
- Temperature measurements
Biological Effects
- Absence of coldwater taxa where they are expected
- Absence of warmwater taxa where they are expected
- Congregation of fish near heated discharges
- Congregation of coldwater fish near ground inputs
Consider contributing, modifying, and related factors as candidate causes when selecting temperature as a candidate cause: