9 Assessment of Pollution of Water Resources and Process of Pollution Spreading
205
When assessing the susceptibility of a lake to degradation, it is necessary to determine
the thermal systems occurring in it.
From the point of view of lake protection, it is unacceptable to keep fish in the
lakes [86]. For example, in the years 1977–1982, as a result of the large-scale rainbow
trout rearing (Oncorhynchus mykiss Walbaum) in I´ nsko, water quality deteriorated
significantly. About 27 t of fish were produced at that time, while the load of organic
pollutants was estimated at 10,000–15,000—equivalent residents. The trophic level
of this reservoir was then defined as the initial stage of eutrophy, whereas it was
previously a mesotrophic reservoir [92]. After stopping the trout breeding, the lake
returned to the a-mesotrophy state at the beginning of the nineties [92]. In Western
Pomerania, the practice of carbon black fish farming was abandoned.
9.5 Assessment Systems for Landscape Water Trophy
Water dynamics, natural catchment conditions, and susceptibility to degradation
determine the quality of water in lakes and the level of their trophies. In Poland,
a method for determining the quality of their waters has been developed for lakes
monitoring purposes [59, 109]. Research in this method is carried out only during
the spring circulation and summer stagnation, and mainly includes surface waters,
and to a lesser extent, near bottom waters (Table 9.3). When assessing the trophy
of lakes, other methods are also used; adopted by the Organization for Economic
Cooperation and Development (OECD), based on: measurements of percentage
oxygenation at the summit of the heterothermal summer of the bottom layer, average
annual and maximum values of measurements: secchi disc visibility (SD), content
in surface waters of total phosphorus and chlorophyll “a” [5]. The method proposed
by Zdanowski [13, 14] is similar, taking into account summer measurements of total
phosphorus and chlorophyll “a” in surface waters and water transparency (SD), as
well as additional indicators (total nitrogen content, N to P ratio, algae biomass and
share of cyanobacteria in biomass). The Carlson method [61] is commonly used,
based on the results of measurements in summer in surface waters of the total phosphorus, chlorophyll “a” and water visibility, transformed into numerical indicators
(lake state trophies—WST), which are a kind of comparable “measure” the level
of advancement of the eutrophication process. The description of these methods of
trophic assessment is presented in Table 9.4. Lange, Ma´ slanka [60] take the position
that for the assessment of the level of trophic lakes, the most appropriate is the analysis of aerobic conditions during the summer stagnation. According to these authors,
oxygen conditions determine the nature, extent, and severity of the basic processes
that form biocenosis. In their analysis, the conclusions as to the susceptibility of the
reservoir to degradation concern the actual course of the eutrophication process and
not the potential determinants. The susceptibility of the lake to degradation determined on the basis of physiographic indicators and catchment may not be directly
related to water quality. The most degraded lakes do not have to be distinguished
by particularly low resilience, because their condition is primarily due to strong
205
When assessing the susceptibility of a lake to degradation, it is necessary to determine
the thermal systems occurring in it.
From the point of view of lake protection, it is unacceptable to keep fish in the
lakes [86]. For example, in the years 1977–1982, as a result of the large-scale rainbow
trout rearing (Oncorhynchus mykiss Walbaum) in I´ nsko, water quality deteriorated
significantly. About 27 t of fish were produced at that time, while the load of organic
pollutants was estimated at 10,000–15,000—equivalent residents. The trophic level
of this reservoir was then defined as the initial stage of eutrophy, whereas it was
previously a mesotrophic reservoir [92]. After stopping the trout breeding, the lake
returned to the a-mesotrophy state at the beginning of the nineties [92]. In Western
Pomerania, the practice of carbon black fish farming was abandoned.
9.5 Assessment Systems for Landscape Water Trophy
Water dynamics, natural catchment conditions, and susceptibility to degradation
determine the quality of water in lakes and the level of their trophies. In Poland,
a method for determining the quality of their waters has been developed for lakes
monitoring purposes [59, 109]. Research in this method is carried out only during
the spring circulation and summer stagnation, and mainly includes surface waters,
and to a lesser extent, near bottom waters (Table 9.3). When assessing the trophy
of lakes, other methods are also used; adopted by the Organization for Economic
Cooperation and Development (OECD), based on: measurements of percentage
oxygenation at the summit of the heterothermal summer of the bottom layer, average
annual and maximum values of measurements: secchi disc visibility (SD), content
in surface waters of total phosphorus and chlorophyll “a” [5]. The method proposed
by Zdanowski [13, 14] is similar, taking into account summer measurements of total
phosphorus and chlorophyll “a” in surface waters and water transparency (SD), as
well as additional indicators (total nitrogen content, N to P ratio, algae biomass and
share of cyanobacteria in biomass). The Carlson method [61] is commonly used,
based on the results of measurements in summer in surface waters of the total phosphorus, chlorophyll “a” and water visibility, transformed into numerical indicators
(lake state trophies—WST), which are a kind of comparable “measure” the level
of advancement of the eutrophication process. The description of these methods of
trophic assessment is presented in Table 9.4. Lange, Ma´ slanka [60] take the position
that for the assessment of the level of trophic lakes, the most appropriate is the analysis of aerobic conditions during the summer stagnation. According to these authors,
oxygen conditions determine the nature, extent, and severity of the basic processes
that form biocenosis. In their analysis, the conclusions as to the susceptibility of the
reservoir to degradation concern the actual course of the eutrophication process and
not the potential determinants. The susceptibility of the lake to degradation determined on the basis of physiographic indicators and catchment may not be directly
related to water quality. The most degraded lakes do not have to be distinguished
by particularly low resilience, because their condition is primarily due to strong