Barbel Society Lancashire Meeting Wedns 23rd

**JayZS** · #1 (**permalink**) 09-02-2012, 09:10

Go look at the following mangled fish picture.

Most hydropower schemes are a waste of taxpayers' money and damaging to the environment, says new report - The Angling Trust

And if you have not already seen it read the downloadable file just below the picture.
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Prompted by the picture I had a think about how Archimedes screws work.
Each "turn of the screw" holds a pocket of water. In the original Archimidean usage of the screw, a handle was turned, which moved the water pockets upstream, thus lifting water from the bottom of the screw, which was usually positioned in a river.
However once electricity had been invented some bright spark realised that an Archimedes screw could be run backwards. The pockets of water, assisted by gravity, could be made to turn the screw and power a generator as they descended. All clever stuff. And in small scale hydro generation these pockets of water discharge into the river by an outlet channel. But such flows of water are very attractive to fish migrating upstream, salmon, seatrout, and apparently even perch. Fish though do not tend to be engineers or scientists. They cannot see that a train of water pockets does not form a continuos water-filled path upstream. They do not know that they cannot get past that first pocket. But it does not stop them trying. So they remain at the lower end of the screw, where the blade is constantly turning, and unsurprisingly get sliced, as in the picture, by the edge of the rotating blade. 7 fish killed in one incident would suggest that most fish swimming into this area will be damaged or killed. Not just the odd one. So it is quite critical that the input and output channels are screened against fish entry.
Unfortunately, especially during Autumn ( when many fish run upstream) there is a great deal of leaf and other debris being swept downstream. This tends to clog up such fish screens. It is not hard to see why hydro
schemes will be unenthusiastic about fitting the screens.
It is vital that ALL micro hydro schemes are fitted with efficient fish filters of suitable mesh size, and that will work at all water levels, both at the upstream and downstream ends.

**admin** · #2 (**permalink**) 09-02-2012, 09:56

I was told in New Mills they jump in the water to clear debris from the inlet on a daily basis when the leaves are falling, H&S anybody EEK!

Was also told that they kicked H2ope to the curb becasue there 9k per year maintenance contract was little more than telephone support.

**JayZS** · #3 (**permalink**) 09-02-2012, 10:07

I need to go look at it, following the post flood repairs. Firstly to see if screens are in place, and secondly to see whether the next flood will again bury the inlet.