Screening and Cleaning

One of the issues raised in Kelham Island Hydro is the importance of adequate screening to prevent juvenile fish from entering the turbine channel from both up and downstream positions. The ideal size is just 3mm x 3mm. To give an idea of how difficult maintenance of such a screen can be, take a look at the before and after pictures below which show the accumulated debris caused by recent flooding at Niagara weir. The 'trash-screen' is at the upstream entrance to the fish-pass.

Before

After

The screen in this case is intended to allow passage of fish and is therefore deliberately large, but if you imagine the amount of debris that will frequently accumulate on much smaller screens intended to stop fish passage, i.e. those that need to be installed on a hydro-power channel, then you can also imagine the levels of maintenance that will be required to ensure that adequate levels of water flow through and keep the turbine running at an optimum. Cost effective? No maintenance costs were factored into the published feasibility survey for Kelham Island.

The maintenance of Niagara fish-pass is undertaken by volunteers working for SPRITE and I'm hugely indebted to that organisation for providing these illuminating images. Keep up the brilliant work!