Brown Plumes Sweep into Shannon Estuary After Heavy Rain

European Space Agency satellite imagery has captured large plumes of silt and soil washing into the Shannon Estuary following heavy rainfall.

Images from the Copernicus Sentinel-2A satellite, taken on Tuesday at midday, show brown plumes spreading from several river mouths, including the River Fergus at Clarecastle, the Crompaun (Crompaan) River at Kilmurry McMahon in West Clare, and in Limerick City, where the Lower River Shannon meets the wider estuarial waters.

Rainfall totals for September are already above average, and further heavy rain is expected in the coming week.

Such plumes occur when prolonged or intense rain increases runoff from fields, hillsides, and riverbanks, carrying soil and organic material into rivers, which then deposit the sediment into bays and estuaries. The effect is particularly visible where freshwater meets the clearer waters of coastal areas.

Ireland’s west coast is especially prone to these events, with high rainfall and catchments composed of loose soils and peat, which are easily eroded. After extended wet periods, large volumes of sediment can be released quickly, potentially altering river mouths and harbours over time.

The Sentinel-2A satellite, equipped with high-resolution sensors, allows scientists and environmental agencies to track changes in land and water quality, providing valuable insight into the impact of extreme weather on Ireland’s waterways.