Temperature
Aquatic organisms are dependent on certain temperature ranges for optimal health. Temperature affects many other parameters in water, including the amount of dissolved oxygen available, the types of plants and animals present, and the susceptibility of organisms to parasites, pollution and disease. Causes of temperature changes in the water include weather conditions, shade and discharges into the water from urban sources or groundwater inflows. Temperature is measured in degrees Celsius (°C). Seasonal trends: May to October: 22 to 35°C, November to April: 2 to 27°C
http://www.lcra.org/water/quality/crwn/indicators.html
Levels of temperatures:
<13C suitable for cold-water species such as trout, mayflies, caddisflies and stoneflies.
13-20C suitable for some salmon, mayflies, caddisflies and beetles.
20-255C suitable for most other fishes, invertebrates and warm water species
>25C lethal to trout, salmon, many aquatic insects and most cold water species.
THE HEA;THIEST RIVER BASED ON TEMPERATURE RESULTS IS: SAVA RIVER