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Hi Steve & All,
Sounds like an earth tides effect---
http://www.dnr.mo.gov/env/wrc/docs/whywaterlevelschange.pdf
DW
----- Original Message -----
From: "David & Alison Webster" <dwebster@glinx.com>
To: <NatureNS@chebucto.ns.ca>
Sent: Monday, July 16, 2012 4:56 PM
Subject: Pump drawdowns: [NatureNS] Freshwater Shortages and Bay of Fundy
Tides
> Hi Steve & All,
> I tried Google Chrome and was able to read where Internet Explorer
> failed namely--
> http://www.hwe.org.ps/Education/Birzeit/GroundwaterEngineering/Chapter%203%20-%20Groundwater%20Flow%20to%20Wells.pdf
>
> This is not light reading but examples 6.3 a&b & 6.4 provide samples of
> effects at a distance from the well. In 6.4 e.g. water table was lowered
> 1m at a distance of 500 m from the well after continuous pumping at 3888
> M^3/day for 4.3 days. This reach is greater than I had remembered but this
> rate is rather large.
> Yt, DW
> ----- Original Message -----
> From: "David & Alison Webster" <dwebster@glinx.com>
> To: <naturens@chebucto.ns.ca>
> Sent: Sunday, July 15, 2012 10:09 PM
> Subject: Re: [NatureNS] Freshwater Shortages and Bay of Fundy Tides
>
>
>> Hi Steve & All, July 15, 2012
>> I wouldn't care to suggest that I have the physics correct; just a
>> very crude first approximation of the effect of head gradients over
>> distance. But way more correct than the one you advance.
>>
>> Except for very simple artificial situations (assumptions that seldom
>> apply in practice) problems of liquid flow in porous media can not be
>> solved analytically and require computer modelling or field measurements.
>> But flow to any sink such as a well, tile drain or Gloosecap's buried
>> garden hose, from a phretic surface, will be at right angles to
>> isopotential lines. I recall this only in vague terms now but as distance
>> from the sink increases there is a dramatic increase in the length of
>> flow paths and transit times.
>> I tried to find a sample representation of pumped well steady-states
>> but keep getting run time errors (started about a week ago with Internet
>> Explorer.
>> Yt, DW, Kentville
>> ----- Original Message -----
>> From: "Stephen R. Shaw" <srshaw@Dal.Ca>
>> To: <naturens@chebucto.ns.ca>
>> Sent: Sunday, July 15, 2012 1:24 AM
>> Subject: Re: [NatureNS] Freshwater Shortages and Bay of Fundy Tides
>>
>>
>>> Quoting David & Alison Webster <dwebster@glinx.com>:
>>>
>>>> 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.
>>>
>>> Dave, Patricia:
>>> I don't know if you have the physics of the above idea correct, Dave,
>>> but if you have, here is a possible suggestion/way out of your
>>> pessimistic assessment.
>>> Suppose that the water table out there is in part a continuous sheet or
>>> lake of (almost) incompressible water that extends all the way from the
>>> farm out to within, say, 1 meter of the Bay of Fundy. Your hydraulic
>>> gradient now rises to 10 instead of your 0.001, and the resulting
>>> forced flow, now feasible, would impress some seawater into the
>>> supposed continuous aquifer under pressure. The resulting pressure
>>> change would be felt very quickly even 10 km inland, explaining the
>>> increase in pressure in the well (as in water coming out of a long,
>>> full hose immediately after the tap (pressure source) is turned on --
>>> no delay). This amounts to saying that there is zero resistance to flow
>>> over 10 km, which is not possible physically because of frictional wall
>>> effects (Poiseuille's law for tubes -- lower flow near the edges), but
>>> you can speculate that this might be a relatively small effect if the
>>> depth of water table is significantly large. A bit of the sea water
>>> would mix in at the edges but most would be removed again at the next
>>> low tide.
>>> I don't know if this is a physically reasonable model of what's down
>>> there, but if it is, it might make the farmer's observation feasible.
>>> Obviously it goes against your belief that the water table is extremely
>>> local. Do geophysicists conceptualize the water table around there as
>>> in part a continuous, shallow underground lake? Someone must have
>>> investigated this if you knew where to look or whom to ask.
>>> Steve (Halifax)
>>>
>>>
>>>> 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