5 Water Resources of Stagnant Waters
77
and extensive melioration works. The rate of transformations of the lake basin from
the moment of its origin to modern times, as a consequence leading to a decrease
in their surface area, was characterised by high fluctuations. It was determined by
two primary factors, namely: lake water level fluctuations (decrease), and filling the
basin with accumulated biogenic and terrestrial sediments. Although in the process
of evolution lakes underwent several stages of similar transformations, they are in
different stages of development of their basins.
An attempt of determination of changes occurring in lake basins in the twentieth
century was presented based on the example of selected lakes in Poland described
in the relatively rich literature.
According to research conducted by various authors, a decrease in the water level
in many lakes by 05–0.7 m caused an evident decrease in their surface area, sometimes
even by 25–30% [15]. In some lakes, the water level decreased by even 2.5 m (Lake
Miedwie) and more (Lake Gopło), causing a decrease in their surface area by more
than 50% [16–18]). Choi´ nski and Madali´ nska [19], analysing bathymetric plans of
lakes in the Masurian and Pomeranian Lake District, concluded that over 60–70 years
in the twentieth century, the surface area decreased by several percent, and the volume
by several tens percent.
In a group of 18 lakes located in the Wielkopolskie Lake District throughout
approximately 50 years, their considerable transformation was observed. Research
evidenced a considerable decrease in the surface area by 14.8% (i.e. 172.6 ha). As
a result of changes in the surface area and shallowing of lakes, water resources
accumulated in the lakes decreased by a total of 7.7%, which constitutes 3.6 million
m
3 [20]. It should be remembered, however, that the transformations are a natural
element of their evolution. In the case of the analysed lakes, evolution is accelerated
by human activity and climate changes.
Mi˛ esiak-Wójcik et al. [21] presented changes in the surface area of stagnant waters
in the western part of West Polesie (East Poland). The research was based on the
analysis of the content of archival topographic maps of Poland at a scale of 1:10 000,
presenting the situation from the early 1980s, and orthophoto maps and satellite
images from the years 2010–2014. The objective of the analysis was the determination of the direction of transformations, as well as the presentation of results at
variance with the opinion commonly adopted in Europe on a progressing decrease
in the surface area of water bodies. The number of objects and their surface area
increased over the last three decades. This resulted from the co-occurrence of natural
factors and human activity, both destructive and aimed at the restoration of postglacial
areas unique at the European scale.
Based on analyses of bathymetric plans of Lake Jamno from 1889 and 1960,
[15] obtained an image of transformations of not only the surface area but also
water resources. Throughout 71 years, the surface area of the lake decreased by
approximately 150 ha, and the volume of the lake decreased by 9.247 thousand m
3 ,
i.e. by 22.7%.
Water level fluctuations in 24 lakes of the Pomeranian Lake District were presented
by D˛ abrowski [22]. The author concluded that in addition to the primary elements
77
and extensive melioration works. The rate of transformations of the lake basin from
the moment of its origin to modern times, as a consequence leading to a decrease
in their surface area, was characterised by high fluctuations. It was determined by
two primary factors, namely: lake water level fluctuations (decrease), and filling the
basin with accumulated biogenic and terrestrial sediments. Although in the process
of evolution lakes underwent several stages of similar transformations, they are in
different stages of development of their basins.
An attempt of determination of changes occurring in lake basins in the twentieth
century was presented based on the example of selected lakes in Poland described
in the relatively rich literature.
According to research conducted by various authors, a decrease in the water level
in many lakes by 05–0.7 m caused an evident decrease in their surface area, sometimes
even by 25–30% [15]. In some lakes, the water level decreased by even 2.5 m (Lake
Miedwie) and more (Lake Gopło), causing a decrease in their surface area by more
than 50% [16–18]). Choi´ nski and Madali´ nska [19], analysing bathymetric plans of
lakes in the Masurian and Pomeranian Lake District, concluded that over 60–70 years
in the twentieth century, the surface area decreased by several percent, and the volume
by several tens percent.
In a group of 18 lakes located in the Wielkopolskie Lake District throughout
approximately 50 years, their considerable transformation was observed. Research
evidenced a considerable decrease in the surface area by 14.8% (i.e. 172.6 ha). As
a result of changes in the surface area and shallowing of lakes, water resources
accumulated in the lakes decreased by a total of 7.7%, which constitutes 3.6 million
m
3 [20]. It should be remembered, however, that the transformations are a natural
element of their evolution. In the case of the analysed lakes, evolution is accelerated
by human activity and climate changes.
Mi˛ esiak-Wójcik et al. [21] presented changes in the surface area of stagnant waters
in the western part of West Polesie (East Poland). The research was based on the
analysis of the content of archival topographic maps of Poland at a scale of 1:10 000,
presenting the situation from the early 1980s, and orthophoto maps and satellite
images from the years 2010–2014. The objective of the analysis was the determination of the direction of transformations, as well as the presentation of results at
variance with the opinion commonly adopted in Europe on a progressing decrease
in the surface area of water bodies. The number of objects and their surface area
increased over the last three decades. This resulted from the co-occurrence of natural
factors and human activity, both destructive and aimed at the restoration of postglacial
areas unique at the European scale.
Based on analyses of bathymetric plans of Lake Jamno from 1889 and 1960,
[15] obtained an image of transformations of not only the surface area but also
water resources. Throughout 71 years, the surface area of the lake decreased by
approximately 150 ha, and the volume of the lake decreased by 9.247 thousand m
3 ,
i.e. by 22.7%.
Water level fluctuations in 24 lakes of the Pomeranian Lake District were presented
by D˛ abrowski [22]. The author concluded that in addition to the primary elements