4 Anthropogenic Water Reservoirs in Poland
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ice phenomena as well as changes in water fertility, shore processes, bottom sediment formation and water body longevity. Among all limnic processes which take
place in water bodies in Poland, of particular importance from the point of view of
the economic utility of these water bodies are variations in thermal conditions, ice
phenomena, water oxygenation, eutrophication and water salinity.
4.5.1 Thermal Conditions
The thermal conditions prevailing in anthropogenic water bodies are influenced by
both natural and man-made factors; natural thermal systems have only been significantly transformed in some bodies of water. Thermal systems typical of the temperate
climate zone predominate. Water bodies with depths of at least a few (or more than
ten) metres are dimictic with a clear and typically anothermal stratification in summer,
catothermal stratification in winter and two homothermal periods. Shallow water
bodies with a medium depth not exceeding 2 to 4 metres are polymictic with more
frequent occurrences of homothermal stratification, which is caused mainly by wind
mixing.
A clear example of human impact on lentic waters is water bodies burdened
with so-called thermal pollution, which exhibit clearly increased or lowered temperature (in relation to the natural temperature of standing or flowing waters under
given conditions) caused by human activity, e.g. heating caused by the inflow of
water, sewage or sediments. A common phenomenon is the burdening of water
bodies with municipal, industrial or household sewage, which raises water temperature in zones where the sewage flows into the water. Just a few water bodies in
Poland are subject to extreme anthropogenic thermal loads. Their thermal regimes
are primarily shaped by discharges of heated water, and the thermal characteristics
of their water have been completely transformed [21]. Examples of water bodies
which retain heated water are the reservoirs near Konin or the Rybnik Reservoir.
Water is sourced from the Rybnik Reservoir, it is heated in the process of cooling
the power units of a conventional power plant and discharged back into the reservoir
basin, which causes water temperature to rise to approximately 6 °C in winter and to
20 °C–35 °C in summer depending on the exact sector of the reservoir. The temperature of water in the reservoir is even 10 °C higher than the average temperature
of other bodies of water (Fig. 4.7). As a result of its water being heated, the reservoir permanently exhibits a stratification similar to the anothermal one with varying
stability with respect to its vertical range and spatial distribution (in the absence of
discharges of heated water, spring homothermia, anothermia, autumn homothermia
and catothermia would reflect thermal transformations within the reservoir). Therefore, the reservoir may be described as an anthropomictic and anthropothermal one
[18].
Local human pressure caused by storing waste or sewage within the water body
basin may result in meromixia; this leads to a peculiar vertical temperature distribution, which is present, e.g. in the Górka Reservoir in Trzebinia. The reason for the
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ice phenomena as well as changes in water fertility, shore processes, bottom sediment formation and water body longevity. Among all limnic processes which take
place in water bodies in Poland, of particular importance from the point of view of
the economic utility of these water bodies are variations in thermal conditions, ice
phenomena, water oxygenation, eutrophication and water salinity.
4.5.1 Thermal Conditions
The thermal conditions prevailing in anthropogenic water bodies are influenced by
both natural and man-made factors; natural thermal systems have only been significantly transformed in some bodies of water. Thermal systems typical of the temperate
climate zone predominate. Water bodies with depths of at least a few (or more than
ten) metres are dimictic with a clear and typically anothermal stratification in summer,
catothermal stratification in winter and two homothermal periods. Shallow water
bodies with a medium depth not exceeding 2 to 4 metres are polymictic with more
frequent occurrences of homothermal stratification, which is caused mainly by wind
mixing.
A clear example of human impact on lentic waters is water bodies burdened
with so-called thermal pollution, which exhibit clearly increased or lowered temperature (in relation to the natural temperature of standing or flowing waters under
given conditions) caused by human activity, e.g. heating caused by the inflow of
water, sewage or sediments. A common phenomenon is the burdening of water
bodies with municipal, industrial or household sewage, which raises water temperature in zones where the sewage flows into the water. Just a few water bodies in
Poland are subject to extreme anthropogenic thermal loads. Their thermal regimes
are primarily shaped by discharges of heated water, and the thermal characteristics
of their water have been completely transformed [21]. Examples of water bodies
which retain heated water are the reservoirs near Konin or the Rybnik Reservoir.
Water is sourced from the Rybnik Reservoir, it is heated in the process of cooling
the power units of a conventional power plant and discharged back into the reservoir
basin, which causes water temperature to rise to approximately 6 °C in winter and to
20 °C–35 °C in summer depending on the exact sector of the reservoir. The temperature of water in the reservoir is even 10 °C higher than the average temperature
of other bodies of water (Fig. 4.7). As a result of its water being heated, the reservoir permanently exhibits a stratification similar to the anothermal one with varying
stability with respect to its vertical range and spatial distribution (in the absence of
discharges of heated water, spring homothermia, anothermia, autumn homothermia
and catothermia would reflect thermal transformations within the reservoir). Therefore, the reservoir may be described as an anthropomictic and anthropothermal one
[18].
Local human pressure caused by storing waste or sewage within the water body
basin may result in meromixia; this leads to a peculiar vertical temperature distribution, which is present, e.g. in the Górka Reservoir in Trzebinia. The reason for the