The Environment Agency said the low oxygen level in Pittville Lake could be algal bloom or sediment stirred up by rain, or both.
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Luke Castiglione with the latest weather forecast. Showers clearing but further rain on the way.
Rain and the ensuing mud hasn't stopped thousands of people enjoying Glastonbury festival
Luke Castiglione with the latest weather. Sunny spells this afternoon, heavy showers - some thundery. Brighter in the West.