Predicting Temperatures of Small Streams

Hourly temperatures of small streams can be accurately predicted using an energy balance. Micrometeorological measurements are required to assess the environment of the small stream accurately. The temperature‐prediction technique was tested on three streams in Oregon. On unshaded stretches, net all‐wave radiation is the predominant energy source during the day; evaporation and convection account for less than 10% of the total energy exchange. Conduction of heat into the stream bottom is an important energy balance component on shallow streams having a bedrock bottom. Up to 25% of the energy absorbed by such a stream may be transferred into the bed. Hourly temperature changes of 0–16°F were predicted to within 1°F more than 90% of the time. This technique permits foresters to control water temperature through manipulation of stream‐side vegetation.