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2020 Acid Waters Programme Complete

26th May, 2020

The Foundation’s operations team have completed this year’s liming programme.

Applying sand lime to a "first order" stream in the headwaters of the IrfonThis annual 2-week task is vital in ensuring acidity in the headwaters of the Wye and Irfon (one of the upper Wye’s major tributaries) does not return to the previously high levels that up until the early 2000s, were damaging fish populations and other aquatic life.

Over the past couple of weeks, our team has distributed 164 tonnes of lime into 91 sites. These are all located at the top of watercourses that drain into the river Irfon and the upper Wye, what are known as “first order” streams.

Without this lime these streams can suffer sudden spikes in acidity after rainfall. pH levels can drop to below 4, wiping out invertebrates and damaging the overall ecology. While these streams may look pristine to us they can be rendered lifeless by these acid spikes, which are a result of years of acid rain, forestry operations and the geology of the area, which has a very poor buffering capability.

With support from partners such as Natural Resources Wales, liming streams has been our way of preventing this damage for over the past fifteen years.

Salmon and trout populations have recovered remarkably since the work started and the Irfon in particular is now one of the best salmon spawning rivers in the Wye catchment.

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