Warunki występowania oraz reżim wydajności i temperatury wypływów wód podziemnych w Sierakowskim Parku Krajobrazowym i w obszarze przyległym
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Date
2005
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Wydawnictwo Poznańskiego Towarzystwa Przyjaciół Nauk
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Abstract
215 sites of natural groundwater outflows
were identified in the Sieraków Landscape Park
and its surrounding area. On the basis of
the criteria adopted, they were divided into
124 single outflow sites, mainly springs, bogsprings
and seeps, and 91 outflow complexes
forming seepage lines and fields, spring lines,
and bog-spring fields.
This abundance of groundwater outflow sites
is due to the morphological diversity of the
terrain and its dense network of glacial troughs
offering plenty of opportunities for groundwater
to get in contact with the ground surface.
Tire observed unevenness in the spatial distribution
of natural groundwater outflows is determined
by the area's geological situation, the
size of its morphological units, and consequently,
the size of the local groundwater basin.
The group occurrence of the outflows can be
accounted for by a comparatively large size of
the outcrops of the saturation layer and the
impermeable bottom layer.
By morphological location, outflow sites are
most numerous in the slope zones of glacial
troughs, many can be found at the foot of the
slopes and scarps, and a bit fewer near stream
channels and on the flat floors of river valleys. It
is also probable that there are outflows in the
bottoms of lake basins. The aquifers feeding the
outflows are usually situated in glaciofluvial
sands and gravels, between till deposits. The
sub-surface water-bearing horizon nourishes
a mere few per cent of the outflows (chiefly
those on the southern slope of the Warta and
Noteć dune interfluve).
The majority of outflows are of layerdescending
character. Only a few display pulsation
indicative of an ascending nature. Predominant among active outflows are
those with a low discharge, under dmV 1 . Outflows
forming complexes have discharges even
in excess of 20 dmV1
. They include: a bogspring
field in a ravine near Chalin, another
south of Lake Chalinek, and the headwater
zones of the Kubek Zachodni and Kubek
Wschodni. The latter produce more than
160 dmV1
. The discharge can be associated
with the density of outflows (the greater their
number, the lower the discharge of individual
sites), the retention capacity of the aquifer
concerned, and the size of the nourished area,
which controls the stability of the discharge.
Among periodic outflows are those draining the
thin, non-isolated sub-surface water level. The
water depletion rate is slower in the more extensive
and thicker inter-till and sub-till levels.
Discharge variations are not sudden and depend
on alimentation through precipitation.
Maximum and minimum discharge periods
follow heavier and reduced rainfalls, respectively.
Depending on the depth of water drained
by the outflows and the nature of the lithology,
the temporal lag relative to the prevalent
external conditions is shorter or longer. The
temperature of outflowing water varies with the
depth of the aquifer being drained and the rate
of underground water circulation. A temperature
of 5~6°C is characteristic of outflows fed
by shallow groundwater (in the winter). Higher
temperatures free from major seasonal variations
(from 9°C to 11°C) can be observed in
outflows draining inter-till levels whose thermal
insulator is the thick till layer.
The above remarks sum up only a preliminary
hydrographie study. The interesting
issues that have emerged need a more systematic
research into the discharge of the outflows
and their temperature and feeding conditions.
It can undoubtedly provide serious and
valuable factual material for a better understanding
of the hydrogeological conditions in
the study area. Such a research seems even
more justified by the fact that there have been
few detailed studies of crenological conditions
in the Polish Plain so far.
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Citation
Badania Fizjograficzne, Seria A, Tom 56, 2005, s. 137-156
Seria
Seria A - Geografia Fizyczna Tom 56;
ISBN
83-7063-456-7
ISSN
0067-2807