The Environment

The use of the Archimedean screw minimizes the environmental impact of a hydro scheme. Of critical importance to the Environment Agency is the distance between where water enters into a hydro scheme and where it exits back into the river – the so-called ‘Depletion reach’. This is the distance over which a river has less water flowing through it because the water has been channelled through a turbine. The smaller the depletion reach, the less impact a hydro scheme has upon the natural environment of a river.

This is one reason why the Archimedean screw is environmentally friendly – the depletion reach is minimized. A second reason is that the Archimedean screw is recognized as being more fish compatible than any other turbine type since there is effectively no pressure difference across it – in other words, fish can travel safely down the screw. Tests have shown that over a wide range of species, the percentage of fish harmed in the process is indeed very minimal and indeed much less than natural predation or loss through angling.

There are of course, other environmental costs of developing any hydro scheme – the environmental impact of the use of concrete and steel, as well as emissions created through the transport of materials for construction. By year 5 of a scheme, such impacts have been offset by the carbon emission savings of hydroelectricity generation. A hydro scheme will typically generate for at least 40 years. Indeed, there are instances of hydro schemes still generating after 100 years.

Set against the immediate environmental effect of a hydro scheme is the very much larger environmental gain. Global warming is caused by the build up of carbon emissions. Hydro schemes reduce the need for fossil fuel generation and therefore have a larger positive, net impact upon the environment.