[NatureNS] slacks - when do they refill?

From: David & Alison Webster <dwebster@glinx.com>
To: naturens@chebucto.ns.ca
References: <CAKqJtz9NfHAnOHg302CG9pPL+dm+Qhwzq5drneGeTFwm5WOTSA@mail.gmail.com>
Date: Fri, 23 May 2014 21:26:36 -0300
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Hi Randy & All,                        A picture helps.
     I remembered that I had a fairly large scale soil map of NS =
(MacDougall & Nowland, 1972; 1:450,000) so dug it out. Your library =
should have one if you don't. And a Google Earth image suggests that the =
slacks are predominantly along the southerly third of Pomquet Beach and =
parallel to the southerly shore of the beach.
    The soil to the west of the west esturary (Monk's Head and south), =
and south west of the east esturary, is Queens; mostly unstructured, =
poorly drained soil high in silt & clay.  So the bottom muds of both =
estuaries, except perhaps where exposed to wave action on sand, are =
likely high in silt & clay and relatively impermeable.=20
    That large nose of land between the two estuaries is Tormantine =
(moderately coarse and medium textured well drained soil) as is Pomquet =
Beach and land east of the east estuary. All of the Tormantine area is =
nearly free of watercourses except for those that drain less permeable =
soil to the south. So, as a rough estimate for this Tormentine costal =
region, at least 60% of the annual ppt. is disposed of by deep =
percolation and that flow has to go somewhere and exit at some lower =
elevation.
    According to Google Earth some of that middle nose is about 85' =
above sea level. [But it also had some of the estuary 8' above sea level =
while much of the slacks area  was 0' so precision is poor.]=20
    Movement of water in soil is directly proportional  to head, =
hydraulic conductivity and cross-sectional area available for flow  and =
inversely proportional to flow length. If there is a sufficiently deep =
layer of permeable bedrock under that nose and under the channel between =
the nose and Pomquet Beach then much of the refill water could be from =
the nose to the south.=20
    I also wonder if the bottom of some of the slacks may have a lower =
elevation than water in these estuaries when rivers are at full flow. =
This would be flow driven by relatively  small head but over a =
relatively short flow path.=20
    Yt, Dave Webster, Kentville
   =20
  ----- Original Message -----=20
  From: Randy Lauff=20
  To: NatureNS=20
  Sent: Friday, May 23, 2014 3:14 PM
  Subject: Re: [NatureNS] slacks - when do they refill?


  I have posted a picture of the slack here: =
http://people.stfx.ca/rlauff/307/PomquetSlack.jpg. One person I asked =
locally thought that the slack filled up again with the autumn rains. =
That's probably right, but I still can't discount snow melt accompanied =
by spring rain. I guess I'll find out this year.


  Randy


  _________________________________
  RF Lauff
  Way in the boonies of
  Antigonish County, NS.



  On 21 May 2014 18:08, nancy dowd <nancypdowd@gmail.com> wrote:

    Maybe it is just evaporation. Water accumulates in the leaf-lined =
slacks in the Spring (rain and melt) and eventually warming temps and =
strong sun evaporate it until it is empty. Over the summer heat and sun =
manage to keep up with the rainfall not allowing it to accumulate for =
any length of time (it must be hot down in those slacks). Then once the =
cooler temps and less intense sun of Fall take over rainwater can =
accumulate once again in the slacks until it freezes.

    Just a guess.

    Nancy

    On 2014-05-21, at 4:39 PM, David & Alison Webster =
<dwebster@glinx.com> wrote:

    > Hi Randy & All,
    >     I had imagined these dunes to be bare sand. With tree cover on =
the peaks and presumably none on the slacks there is another effect that =
will increase effective ppt in the slacks; sublimation on the tree =
canopy in calm weather and selective snow accumulation in treeless areas =
(roads, glades, etc) in windy weather due to less turbulence and less =
speed over glades..
    > Yt, DW
    > ----- Original Message -----
    > From: Randy Lauff
    > To: NatureNS
    > Sent: Wednesday, May 21, 2014 9:57 AM
    > Subject: Re: [NatureNS] slacks - when do they refill?
    >
    > Thanks folks,
    >
    > I haven't been there in winter, despite my being in NS now for =
over 20 years.
    >
    > Here's the landscape picture though. Picture an accordion, partly =
open lying on its back. The bellows represent the dune system at =
Pomquet, there are peaks and troughs (slacks), and precious little other =
elevations going on. At the slack in question, the surrounding peaks of =
the dunes are dominated by white pine and oak, with other trees as well.
    >
    > Fred asked, if the dunes are sandy, how are they holding water in =
the first place? Basically, I think there is leaf litter which may be =
accumulating in the slack to slow the water seepage. Further to Anne's =
email, the slack in question is well back from the salt water, I suspect =
there is no salt to speak of in that water. Mosquitoes are there in the =
billions, peepers are deafening, both suggesting fresh water (though I =
realize a few mosquitoes can tolerate brackish water).
    >
    > Randy
    >
    > _________________________________
    > RF Lauff
    > Way in the boonies of
    > Antigonish County, NS.
    >
    >
    > On 20 May 2014 18:24, David & Alison Webster<dwebster@glinx.com> =
wrote:
    > Hi Randy & All,                            May 20, 2014
    >     I don't have a clear picture of the topography, either dune or =
inland, but one possible source of water in the slacks is drifting of =
snow into pools.
    >
    >     In woods south of Kentville, where I used to walk in winter, =
pools in woodland cradlehollows of swampy sites never froze. With 2'-3' =
of snow on the ground, the air cone was typically about ~1' across at =
snow level and 4" across at water level. Even at -20o C, with heavy =
snowfall, 60 mph winds and drifting snow  there would be no hint of ice. =
From the viewpoint of ppt per unit area these cones act as black holes; =
snow blows into them but, soon being water, can not escape. These air =
cones were absent when snow was not deep enough to act as a good =
insulator. With sufficient snow cover drifted ~level over the swamp, the =
soil at the base of cradlehollows would warm sufficiently by ground heat =
from below to melt overlying snow and eventually generate one of these =
air cones.
    >
    >     If these pools were sufficiently above the water table then =
they would tend to be transient but, in most soils (given sufficient =
iron and decomposable organic matter), infiltration rate at constant =
head will gradually slow due to formation of a local iron pan over =
decades or centuries. This effect interested me because ortstein is =
sometimes very scattered; patches 3-4' wide and 10-15' apart and these =
pools that collect below air cones could account for this. Also =
prolonged wetting will slake any so