Issue 9: Thermal |
| Description |
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Thermal pollution is often defined as a reduction in water quality caused by increasing its temperature due to disposal of waste heat from industrial or power generation processes. However, other sources of thermal pollution include stormwater running off warmed urban surfaces; removal of trees along rivers exposing the water to direct sunlight; and elevated suspended solids due to soil erosion. As water temperature rises, the rate of photosynthesis and plant growth also increases increasing the need for dissolved oxygen in the water. The metabolic rate of organisms also rises with increasing water temperatures, resulting in an even greater oxygen demand. The life cycles of aquatic insects tend to increase in warm water. Animals that feed on these insects can be negatively affected particularly birds that depend on insects emerging at key periods during their migratory flights. Most aquatic organisms have adapted to survive within a range of water temperatures. Some organisms prefer cooler water, such as trout and stonefly nymphs, while others thrive under warmer conditions, such as dragonfly nymphs and carp. As the temperature of a river increases, cool water species will be replaced by warm water organisms. Temperature also affects the sensitivity of aquatic life to toxic wastes, parasites, and disease. For example, thermal pollution may cause fish to become more vulnerable to disease, either due to the stress of rising water temperatures or the resulting decrease in dissolved oxygen. |
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GIWA definition |
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Thermal refers to the adverse effects of the release of aqueous effluents at temperatures exceeding ambient temperature in the receiving water body. |
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Environmental impacts |
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1. Population/community changes 2. Barriers to migration 3. Displacement of organisms 4. Changes to physical environment |
Indicators | |
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The following are environmental impact indicators for thermal issues. Select the environmental impact indicators that are relevant from the list below and input data into the appropriate indicator sheets. | |
| PAR |
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| PROX |
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