[NatureNS] Freshwater Shortages and Bay of Fundy Tides

From: Patrick Kelly <patrick.kelly@dal.ca>
To: naturens@chebucto.ns.ca
Date: Sat, 14 Jul 2012 22:41:40 -0300
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I recall one of Roy's talks on the tides in the Bay of Fundy. He  
mentioned that when the tide is in all the way, especially on a  
particularly high tide, the weight of all the water actually depresses  
the Earth's crust by several centimetres. I'm not sure if that would  
be sufficient to "force" more water into a depleted aquifer.

The best explanation you will likely find for the tides is in the RASC  
Observer's Handbook. http://www.rasc.ca/handbook  It is written by the  
same Roy Bishop that Doug Linzey mentioned!

Pat


On Jul 13, 2012, at 6:57 PM, David & Alison Webster wrote:

> 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
>>
>>
>>
>>
>> -----
>> No virus found in this message.
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>
>


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Patrick Kelly
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Dalhousie University
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<html><body style=3D"word-wrap: break-word; -webkit-nbsp-mode: space; =
-webkit-line-break: after-white-space; ">I recall one of Roy's talks on =
the tides in the Bay of Fundy. He mentioned that when the tide is in all =
the way, especially on a particularly high tide, the weight of all the =
water actually depresses the Earth's crust by several centimetres. I'm =
not sure if that would be sufficient to "force" more water into a =
depleted aquifer.<div><br></div><div>The best explanation you will =
likely find for the tides is in the RASC Observer's Handbook.&nbsp;<a =
href=3D"http://www.rasc.ca/handbook">http://www.rasc.ca/handbook</a> =
&nbsp;It is written by the same Roy Bishop that Doug Linzey =
mentioned!</div><div><br></div><div>Pat</div><div><br></div><div><br></div=
><div><div><div>On Jul 13, 2012, at 6:57 PM, David &amp; Alison Webster =
wrote:</div><br class=3D"Apple-interchange-newline"><blockquote =
type=3D"cite"><div>Hi Patricia &amp; All, =
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&