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| Titel |
Lakes-paleolakes cascade system and its role in shaping the runoff and chemical properties of water in the young-glacial catchment - example from the Tuchola Pinewood Forest (Northern Poland) |
| VerfasserIn |
Piotr Gierszewski, Dariusz Brykała, Michal Kaszubski, Birgit Plessen |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250126059
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| Publikation (Nr.) |
 EGU/EGU2016-5736.pdf |
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| Zusammenfassung |
| The impact of paleolake basins, filled up with organic mineral deposits, in the transformation
of the chemical properties of the outflow is generally ignored. Defining their role and
importance in the water and matter cycles is one of the objectives of the hydrological and
hydrochemical monitoring, which has been run in the catchment of Lake Czechowskie since
mid-2012.
The axis of the Lake Czechowskie catchment is a hydrographical system made of river
and lake sections. Lake sections are not only present-day lakes (Głęboczek and
Czechowskie), but also basins of the lakes functioned in the past, which are now biogenic
plains. Lake sections of the system are connected by short valley sections, mostly of a gap
character. The size and variability of surface water runoff from the basin is mainly affected
by groundwater and the size of evaporation. Stable groundwater table provides
stability of the river discharge, even during the periods of significant precipitation
deficit.
Groundwater fluctuation ranges registered during the period from May 2012 to September
2015 were between 0.17 and 1.25 m. The smallest were in the deepest piezometers located
in watershed areas, and the largest in the shallow groundwater of lake terraces.
The small dynamics of the groundwater states is reflected by slight fluctuations of
water levels in Lake Czechowskie, which in the analyzed period amounted 0.40
cm.
The surface of paleolake Trzechowskie, cut by a system of drainage ditches, is the area
where an essential part of the surface runoff from the monitored catchment is formed. Large
water resources in this part of the catchment are evidenced by the specific runoff value, which
amounts to 25 dm3s−1km2. It is much larger than the whole basin specific runoff which
reaches 11 dm3s−1km2. The measurements showed that the average surface runoff from Lake
Czechowskie in the analyzed period was 0,065 m3s−1 and was similar to the size of the
water influx via watercourses supplying the lake. On the basis of this value it was
calculated that the theoretical time to replace the water in Lake Czechowskie is 2.8
years.
The hydrochemical study showed that the studied ground- and surface waters
represent the same bicarbonate-calcium-sulphate hydrochemical type. Against the
background of a homogeneous ionic composition, the spatial variation of their overall
salinity is very large. This is reflected by the values of electrolytic conductivity,
which in the study period ranged from 76 to 1218 μS⋅cm−1. The most mineralized
(700-800 μS⋅cm−1) are the waters of streams migrating in the organic-carbonate
formations of the paleolakes and shallow groundwater in these areas. The lowest
mineralization is showed by the groundwater circulating in sandy sediments of outwash
plains. Mineralization of the Lake Czechowskie water of approx. 340 μS⋅cm−1 is a
result of supplying the lake from both sources and the effect of biogeochemical
processes occurring in the lake. The hydrochemical monitoring results showed
that the zones of water enrichment in salts are associated with paleolake basins
filled with the organic-carbonate sediment, while the salt precipitation zones with
lakes.
The results of the study of matter flow in the basin of Lake Czechowskie showed that
paleolakes equally affect the runoff volume and the transformation of the chemical properties
of the water circulating in the basin as the lakes functioning today. The lakes and paleolakes
create a cascade system of interconnected basins. Depending on the place they occupy in
the cascade, their effect on the water circulation and transformation of matter is
different.
This study is a contribution to the Virtual Institute of Integrated Climate and Landscape
Evolution Analyses – ICLEA– of the Helmholtz Association, Grant No VH-VI-415. |
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