High flows

From our farm visits we see just how many fields have damaged and compacted soils, including many that are receiving high level environmental payments.

This reduces markedly the rate at which rain infiltrates into the ground, meaning a damaged soil can generate run off from little more than drizzle. If you have a storm, almost all the water runs off. This overland flow runs onto roads, into houses and causes rivers to rise into large muddy spates.

Low flows

Less rain infiltrating the ground also means that aquifers are not recharged and low flows in summer are exaggerated and prolonged.

The effect on fish species

The problems for fish of extreme high flows is what is called “redd washout”. This is when gravel beds are moved by the high flows, displacing the eggs.

Extreme low flows cause all kinds of problems for fish, especially salmonids, as warmer water carries less oxygen. The worst case scenario is the mass mortalities suffered by the Wye salmon in the famous drought of 1976. Other problems can be less noticeable – many fish species stop feeding during the stress of drought conditions.

See here for details on how we are tackling this issue.