WHY BRIGG GETS GREEN BLANKET IN SUMMER

TIMESCALE: Picture to illustrate the article taken by Ken Harrison in 2011.

BY KEN HARRISON, BRIGG

I see that the annual occurrence of a blanket of green duckweed is accumulating around County Bridge, Brigg.

Essentially, the River Ancholme is a captive river; its flow is regulated both by the release of over-flow at the South Ferriby sluice and the variable amounts of run-off from surrounding fields after rain.

There are two main notions why duckweed becomes regularly prevalent in the Ancholme during the late summer months.  Warmth and the amount of sunlight play a part in both ideas.

One suggestion is that run-off, which to a degree, feeds the river contains diluted amounts of fertilizer that farmers have used on their fields.  Obviously, the fertilizer was originally intended to improve crop growth, but, equally, any alleged fertilizer contaminates entering the river would also benefit water-borne plant growth.

However, the bigger truth appears to be that the source of plant growth nutrients  lies some distance from the Ancholme Valley.

The annual rainfall over northern Lincolnshire is, generally, insufficient to maintain the expected water-level in the Ancholme and, obviously, topping-up cannot be achieved by taking water from the salty Humber.

South of Brandy Wharf, regulated piped water, from the Witham and Trent areas feed the river.  It is understood, that such water can contain phosphates, from, for example, everyday washing liquids and powders. and when combined with prolonged sunshine hours and warm water temperatures, the phosphates promote duckweed and other river-plant growth, as one sees about Brigg around August.

Whether the small duckweed blanket around County Bridge remains fragmented, or spreads like a green-like highway depends upon the combination of weather and the amount of chemicals in the river.