What are Stream Velocity & Discharge?

Stream velocity is how fast the water is moving. You are used to measuring velocities with the speedometer in cars. The speedometer reports velocity as miles per hour. In science, we use the metric system, so we will use meters per second (m/s). It is the same idea, just with different units. Stream Discharge is how much water is moving at this velocity. Discharge is reported as m3/s.

How does Discharge increase?

  1. After a rainfall, more water washes into the stream.
  2. During the spring, snow in the mountains melts and drains down mountain rivers.
  3. Seepage of water beneath dams can increase the amount of water that flows in a stream or river.

How does Discharge decrease?

  1. Drought conditions can occur if there is a low snow pack in the winter or smaller amounts of rain in the spring, summer and fall.
  2. Dams can decrease the amount of water in a river or stream.
  3. “Water rights” are laws that dictate how much water can be taken out of certain rivers, streams and irrigation canals. These “diversions” affect how much water flows at the surface.

How do humans impact Discharge?

Spring Creek has several notable features. It is dissected by the Horsetooth Reservoir to the west. Seepage under the dam helps keep Spring Creek flowing all year. It also has a smaller holding reservoir west of Center Avenue. This pond has a spill gate that can be raised or lowered to control the amount of water flowing at any given time. Irrigation water diverted from the Poudre river joins Spring Creek in this pond as well. So, linking velocity and discharge to precipitation is not that easy.

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Students using a catch to measure stream velocity

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