Run of the River

The technological approach being implemented for the Tacana project and other prospective projects is known as “run of the river” hydroelectricity. In this type of hydroelectric generation, the power itself is created by the natural course of the river current – in short, the natural flow and elevation drop are used to generate electricity. Power stations of this type can only be employed effectively on rivers with a consistent and ample flow. Run of the river projects are dramatically different in design and appearance from conventional dams, and their overall environmental impact is substantially reduced. Ordinary hydroelectric projects constructed on rivers with significant seasonal fluctuations require a large reservoir in order to be productive during the dry season. This usually means that large tracts of land need to be impounded and flooded to enable continuous operation. In stark contrast, run of the river projects simply divert a small amount of water into a penstock pipe, which channels the water downhill to the power station turbines.

    This system uses the basic laws of physics to ensure a steady power supply even in the absence of a huge reservoir.  Because of the difference in relief as water travels down the penstock, potential energy from the water up river is transformed into kinetic energy during its descent.  This gives the water flow ample speed to spin the turbines in the powerhouse, which in turn transforms the kinetic energy into electrical energy.  This method also leaves downstream flows intact, since all diverted water is returned to the stream below the powerhouse.

    Most run of the river power plants consist of a dam across the full width of the river to provide the head needed for running the turbines.  The water that is not needed for generating electricity spills over the dam at a spillway.  Such installations have a reservoir behind the dam, but flooding is minimal and the reservoir is not used to store water for later generation.  Flooding the upper part of the river is not required as it doesn’t need a large reservoir.  As a result, people living at or near the river don’t need to be relocated, and natural habitats are preserved.  This reduces the environmental impact and is a friendlier alternative to the large-scale reservoirs that are a staple of major dams without run of the river design.