THE residents of Avoncliff are right to be concerned about the impact a hydro-power turbine will have on the River Avon, and those who enjoy it now, and future generations. 
The 17th-century Packhorse Bridge at Tellisford had for decades been regarded as an outstanding beauty spot with the River Frome (old English meaning ‘sparkling water’) glistening beneath. Not now, which is very sad and a loss to future generations.
During the summer a casual observer can see that the riverbed under the Packhorse Bridge is heavily silted, covered in algae and devoid of plant life whereas the fast-flowing Mill Stream and the main river from the point the Mill Stream re-joins it have healthy beds of Water Crowfoot supporting a diverse range of invertebrates – food for fish and birds. At times in the summer, the stretch under the bridge has appeared to be almost static.
Whilst 0.5 cubic metres per second may be all that’s required to operate a hydro-power turbine, the Mill at Tellisford has rarely operated at a such a low volume – between December 7 and December 11 this year the volume through has been between 1.5 and 4.5 Cu M/sec. Over recent years even during very dry summers when the River Frome was at lowest this observer has 
noted the Mill diverted in excess of 1.0 Cu M/Sec.
The Environment Agency formally monitors hydro-power installations. It describes the stretch of the River Frome between the beginning and the end of the millstream where the water re-enters the main river as the ‘depleted stretch’ for obvious reasons and compares it with a stretch downstream called the ‘control stretch’. 
The depleted stretch at Tellisford passes under the Packhorse Bridge. In its March 2013 report the EA noted that due to there being less water for dilution in the depleted stretch phosphates are more concentrated and this is encouraging a change in the ecosystem of the river at that point. 
Time will tell but it looks like the hydro-power turbine at Tellisford is not without cost to the river, our enjoyment of it and the pleasure it could give future generations.
R Henderson