Friday, January 13, 2012

What is the "Rondeau Watershed"?

Or, for that matter, what is a watershed anyway?

The term, "watershed" came into English use around 1800 and is used to describe a lowland that acts as a drainage or catchment basin, adjacent to a river or larger body of water. The root, "shed" comes from the Old English verb "sceadan" meaning to divide or separate, or slough off.

Watersheds are significant landscape features with defined boundaries, common physical features, specific habitats and where communities of adapted species, live and reproduce. Drainage flow from surrounding uplands is buffered by woodlands grasslands and marshes. What this means, in a functional watershed, is that the rate of flow is spread out over a longer period of time, the water velocity is slower and suspended sediments are less likely to be washed into lakes. As well, functional watersheds, with a canopy of trees, cool the water and provide breeding and feeding habitat for fish and invertebrates.

Watersheds are characterized by networks of streams in the uplands and lower wetlands like bogs sloughs and marshes. The Rondeau Watershed extents south of the Blenheim moraine (Talbot Street) to Rondeau Bay, East to Road 51, (Kent Bridge Road) and West to Road 12, (Erieau Road). This area comprises a 125 square kilometer drainage basin.


Watersheds also change the chemistry of out flowing waters by providing time for the slightly acidic rainfalls to dissolve minerals, essential for aquatic species. Nutrients like nitrogen and phosphorus, which are a byproduct of plant and animal decomposition, normally leach into surface runoff at a relatively constant rate. Algae and microorganisms establish colonies on surfaces within streams and watercourses and act as biological filters that can remove significant portions of Nitrogen and Phosphorus. Where watercourses widen and slow, beds of organic muck containing trillions of microorganisms metabolize the nitrogen in the absence of oxygen producing methane. In marshes and within the water, green plants take up as much phosphorus as they can and grow. Remaining phosphorus produces algal growth and can, when excessive lead to algal blooms.

To sum up, watersheds slow, cool and clean runoff water.

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