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Hi Patricia & All, July 13, 2012
I don't know Greg Gerrits but I do know Elmridge Farm produce; top
quality and this implies unusually good management. So I would be inclined
to accept his observation of well replenishment rates as a function of
something to do with tides but it can not caused directly by height of
saltwater in the 'nearby' shore.
Flow of any liquid in a porous medium is directly proportional to
hydraulic gradient (head z/lateral displacement y) and inversely
proportional to resistance. A head difference of 10m over lateral
displacement of 10 km (hydraulic gradient = 0.001) would induce essentially
zero flow Or approaching this from the other direction, when water is
pumped exhaustively from a well the water table (drawing on memory) is
seldom lowered beyond a radius of 50 metres.
I would suspect that a tidal effect leads to a local artificial
hydraulic gradient. In effect, water running uphill to the well (and well
vicinity) during this peak inflow period.
I ran into NatureNS by accident some years ago while trying to find some
understandable explanation of tidal effects on the internet. The nearest I
have come to an explanation was some oracular comment to the effect that it
is explained by math that almost no one understands. But meanwhile the tides
come in and go even though I don't understand how it works.
YT, Dave Webster, Kentville
----- Original Message -----
From: "P.L. Chalmers" <plchalmers@ns.sympatico.ca>
To: "NatureNS" <naturens@chebucto.ns.ca>
Sent: Friday, July 13, 2012 2:28 PM
Subject: [NatureNS] Freshwater Shortages and Bay of Fundy Tides
> For most of my life, my family home in Bedford was dependant on a drilled
> artesian well, as there was no municipal water supply in our
> neighbourhood. This is no longer the case, but I am still acutely aware
> of how valuable water is, and curious about hydrology. I was in the
> Annapolis Valley last week and saw how very dry the fields and orchards
> were there. So last Saturday, at the Halifax Seaport Farmers' Market, I
> was asking some of the farmers how they were getting on in the present
> drought.
>
> I had an interesting chat with Greg Gerrits of Elmridge Farm. Since there
> was so little snow last winter, and since it was such a dry spring, his
> normal water supply is down at least 40% from normal levels. He doesn't
> have enough water to irrigate more than a few acres at a time. However,
> he went on to explain the influence of the Bay of Fundy tides on his water
> supply. He said that the weight of incoming water in the Bay was
> sufficient to exert pressure on water deep below the ground, even where he
> farms (near Sheffield Mills, I think). The flow of fresh water into his
> well improves significantly when the Bay is full of salt water. So he has
> learned to schedule his irrigation so that it begins three hours before
> high tide, and stops three hours after high tide.
>
> There are so many kinds of knowledge that a successful farmer needs to
> have, but it hadn't occurred to me that a knowledge of the tides was one
> of them. I may not be representing this very well, but I found it
> intriguing; perhaps someone could say more?
>
> Patricia L. Chalmers
> Halifax
>
>
>
>
> -----
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