Stream power is an important concept in geology and geography that is defined as the rate of energy dissipation (or loss) against the beds or banks of a body of water (such as a stream or lake). The concept of stream power is used commonly in models of landscape change, as water flowing in a stream or river can dramatically change the surrounding landscape over the course of years. Calculating stream power is relatively straightforward.

Multiply the density of water, typically 1,000 kg per meters cubed (kg/m^3) by the acceleration due to gravity, which is 9.81 meters per seconds squared (m/s^2) at sea level. The product of these two numbers is 9,810 kg per meters squared seconds squared (kg/m^2 s^2). Call this result A.

Multiply result A by the hydraulic discharge of the stream. As an example, assuming the hydraulic discharge is 10 meters cubed per second (m^3/s), the result is 98,100 kg m/s^3. Call this result B.

Multiply result B by the slope of the channel to get the stream power. Concluding the example, if the channel slope is 3 meters, then the product of this number with result B gives 294,300 Watts (W, which is the unit of measurement of power). This is the stream power.

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