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Index of Subjects --Apple-Mail-246--1062919565 Content-Type: text/plain; charset=US-ASCII; format=flowed; delsp=yes Content-Transfer-Encoding: 7bit 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. >> Checked by AVG - www.avg.com >> Version: 2012.0.2193 / Virus Database: 2437/5128 - Release Date: >> 07/12/12 > > = = ======================================================================== Patrick Kelly Director of Computer Facilities = = ======================================================================== Faculty of Architecture and Planning Dalhousie University = = ======================================================================== MAIL COURIER PO Box 15000 5410 Spring Garden Road Halifax, Nova Scotia B3H 4R2 Halifax, Nova Scotia Canada Canada = = ======================================================================== Phone:(902) 494-3294 FAX:(902) 423-6672 E-mail:patrick.kelly@dal.ca = = ======================================================================== --Apple-Mail-246--1062919565 Content-Type: text/html; charset=US-ASCII Content-Transfer-Encoding: quoted-printable <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. <a = href=3D"http://www.rasc.ca/handbook">http://www.rasc.ca/handbook</a> = 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 & Alison Webster = wrote:</div><br class=3D"Apple-interchange-newline"><blockquote = type=3D"cite"><div>Hi Patricia & All, = &