Chapter 6: Runoff (R)

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Chapter 6: Runoff (R)

Post by admin » Tue Oct 06, 2015 9:37 am

Originally posted by Rem Westland - 03/10/2013

And now we get to a big one! While an accurate measure of runoff (rain that falls onto land and runs from there into the Lake) would be difficult, a rough estimate by calculating the area of land all around the Lake some 300 metres from shore could begin to tell us how much water runs into the Lake when it rains. Volume of rain, hardness of the land (early frost), cleared areas, and so on will all make a difference. Our current understanding is that runoff from land is a major source of nutrients which feed aquatic plants (good and bad) and can lead to toxic algae. The problem is less the steady fall of rain in the course of a Summer than the intense periods of rain storm that was nutrients directly off the surface of the land into the Lake. One of the observed effects of climate change has been the increasing incidence of violent storms.

In the opening discussion we combine runoff and groundwater because that is how the data for Eastern Ontario are currently available. It reflects the logic that all precipitation that works its way into our Lake will get there either by falling directly onto the lake water (P) or by running over the land or into it (and joining the water table). Eventually, however, I would love to get to a point where we can distinguish between what washes into the Lake over our properties (we can do something about that!) and what seeps into the water table anywhere in the watershed. The latter volume of water will be affected by farming practices, management of wetlands, salting of the roads, disposal by inland residents, and so on. Both types of runoff need to be as benign as possible for our Lake but we SLPOA members can influence the inland aspect of this primarily through local and provincial politicians.
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Re: Chapter 6: Runoff (R)

Post by admin » Tue Oct 06, 2015 9:38 am

Originally posted by Rem Westland - 07/10/2013

An article titled "Combating Climate Change Impacts on Phosphorous in the Grand River and to Lake Erie" by James P. Bruce (24/09/2013) concludes that, although some increase in phosphorous concentrations in water bodies is due to changes in land use and farming practices, the most important cause is heavy rain or rain on snow, and runoff events in a changing climate. It seems to me that anything we can individually do to reduce the amount and/or rate of runoff from our properties into the Lake might make more of a contribution to the improvement (or slower deterioration) of water quality than other actions. I wonder about the benefit, for example, of us property owners with shoreline spending time and effort (and a bit of money!) to create terrasses of earth and rock - covered by vegetation (and no fertilizer!) - to slow down or stop the run of rain water and Spring melt directly into the Lake. If any reader(s) have information on this...please send it in! Thanks.
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Re: Chapter 6: Runoff (R)

Post by admin » Tue Oct 06, 2015 9:39 am

Originally posted by Rem Westland - 08/10/2013

Advice to me from Ralph Pentland, an at-large member of the executive, calls for another update...
A separation between groundwater and surface water appears to be a distinction without much of a difference. All groundwater becomes surface water eventually. In our part of Ontario water runoff in eastern Ontario watersheds is about 1.1 cubic feet per second (cfs) per square mile. So runoff directly to Sharbot Lake will be equal to 1.1 cfs times the land portion of the Sharbot Lake watershed in square miles.

If we assume the basin land surface area around our Lake is 35 square miles the estimated run off would be about 38 cubic feet per second.
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