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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 soil aggregates and decrease infiltration rate.=20
Getting back to dunes, in the idealized case of parallel linear =
dunes and linear slacks and in deep snow conditions I would expect =
linear narrow pools at the base of linear narrow trenches in the snow; =
V-shaped deposits of ortstein if dunes are stable and not advancing.=20
Have you been there in winter and if so does any of this register ?
Yt, Dave Webster, Kentville=20
----- Original Message -----=20
From: Randy Lauff=20
To: NatureNS=20
Sent: Tuesday, May 20, 2014 4:20 PM
Subject: Re: [NatureNS] slacks - when do they refill?
Thanks Fred, but in a dune system, wouldn't that mean that the slacks =
would be less than half full with water? These are sand dunes...very =
porous, so I'm suspecting water leaching in from the hills of the dunes =
into the slacks just couldn't fill them. This is unlike the condition in =
vernal pools where there can be ample elevation around from which water =
could leach in to the pool area. I'm thinking there has to be a =
significant rain or snow fall to fill them.
Randy
_________________________________
RF Lauff
Way in the boonies of
Antigonish County, NS.
On 20 May 2014 15:30, Fred Schueler <bckcdb@istar.ca> wrote:
On 5/20/2014 2:18 PM, Randy Lauff wrote:
Between several of the dunes at Pomquet Beach, Ant. Co., the =
slacks (the
troughs between dune crests) fill with water, but by summer are =
dry. I
guess I've just never been there at the right time to see when =
they fill
again...it can't be just from winter melt water, since the slacks =
are
almost full (and snow melts to about 10% its volume as water). Do =
the
autumn rains fill them again, or the spring rains? Or is it a
case-by-case scenario, which I'd just have to monitor?
* I had the same thought about vernal pools at the CARCNET meeting =
at Quebec City in 1999, during a presentation on Marbled Salamanders, =
which come down into the vernal pools to lay their eggs on the dry =
pondbed in the fall, and stay with them all winter. It turns out that =
the vernal pools fill from the water table, as one would think sandy =
dunes would. And yes, I've been monitoring water level in our local Wood =
Frog ponds, fall and late winter, ever since then.
fred.
------------------------------------------------------------
Frederick W. Schueler & Aleta Karstad
Daily Paintings - http://karstaddailypaintings.blogspot.com/
Vulnerable Watersheds - http://vulnerablewaters.blogspot.ca/
study our books - http://pinicola.ca/books/index.htm
RR#2 Bishops Mills, Ontario, Canada K0G 1T0
on the Smiths Falls Limestone Plain 44* 52'N 75* 42'W
(613)258-3107 <bckcdb at istar.ca> http://pinicola.ca/
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<DIV>Hi Randy & All, =
=20
=
May=20
20, 2014</DIV>
<DIV> I don't have a clear picture of the topography, =
either=20
dune or inland, but one possible source of water in the slacks is =
drifting of=20
snow into pools.</DIV>
<DIV> </DIV>
<DIV> In woods south of Kentville, where I used to =
walk in=20
winter, pools in woodland cradlehollows of swampy sites never froze. =
With 2'-3'=20
of snow on the ground, the air cone was typically about ~1' across at =
snow level=20
and 4" across at water level. Even at -20o C, with heavy=20
snowfall, 60 mph winds and drifting snow there would be no =
hint of=20
ice. From the viewpoint of ppt per unit area these cones act as black =
holes;=20
snow blows into them but, soon being water, can not escape.=20
These air cones were absent when snow was not deep enough to =
act as a=20
good insulator. With sufficient snow cover drifted ~level over the =
swamp,=20
the soil at the base of cradlehollows would warm sufficiently by =
ground=20
heat from below to melt overlying snow and eventually generate one of =
these air=20
cones.</DIV>
<DIV> </DIV>
<DIV> If these pools were sufficiently above the water =
table=20
then they would tend to be transient but, in most soils (given =
sufficient iron=20
and decomposable organic matter), infiltration rate at constant =
head will=20
gradually slow d