Causes of Lake Area Changes in Poland

June, 2011
Journal of Resources and Ecology
J. Resour. Ecol. 2011 2(2) 175-180
Vol.2 No.2
Report
DOI:10.3969/j.issn.1674-764x.2011.02.011
www.jorae.cn
Causes of Lake Area Changes in Poland
Adam CHOIŃSKI1, Agnieszka ŁAWNICZAK2, Mariusz PTAK1 and Leszek SOBKOWIAK1*
1 Institute of Physical Geography and Environmental Planning, Adam Mickiewicz University, 61-680 Poznań, Poland;
2 Chair of Ecology and Agricultural Environment Protection, Poznań University of Life Sciences, 60-649 Poznań, Poland;
Abstract: The northern part of Poland is occupied by numerous lakes formed during the last glaciation
as a result of the Scandinavian ice sheet. Studies carried out in the lake district areas show progressive
reduction of the surface area of the lakes, which leads to their eventual disappearance. The paper
discusses the degree of the observed changes and points out main natural and anthropogenic factors
influencing changes of lake area in Poland, including climate change, depth of lake basins, biomass growth,
deforestation, hydrotechnical works, use of fertilizers and discharge of wastewater.
Key words: Northern Poland; lake districts; lake area changes; natural factors; anthropogenic factors
1 Introduction
Among the areal hydrographic objects lakes deserve
special attention. They play a vital role in the continental
part of the hydrological cycle (e.g., precipitation, runoff,
retention), they are also important for biodiversity and
economy. The growth of many sectors of economy, as
energy industry, agriculture, tourism, etc. would not be
possible without the proximity of water; for that reason
in areas devoid of lakes artificial reservoirs are often
created. Also the immeasurable, aesthetic values of lakes
diversifying the landscape have to be pointed out.
The presence of most lakes in Poland, as in many other
parts of Europe, results from the Scandinavian ice sheet
activity during the last glaciation (Fig. 1).
Lake basins are subject to constant evolution. Its stages
can be defined by characteristic morphometric parameters
of the individual lake or physico-chemical properties of its
water. Every lake, as a concave geomorphological form, is
at a certain point of that evolution, leading to the ultimate
disappearance of the lake. The pace and direction of
these changes may differ, since they depend on a number
of factors, including climate, genetic type of lake basin,
land use patterns, degree of anthropopression and other.
Received: 2010-05-11 Accepted: 2011-01-14
* Corresponding author: Leszek SOBKOWIAK. Email: [email protected].
Lakes are relatively short-lived elements of the landscape.
Choiński (2007) defined the age of lakes in Poland at
2000-3000 years and predicted their lifetime, assuming the
current pace of shallowing, for just few hundred years.
Fig.1 Percentage of lake cover in Europe (after
Kmicikiewiczowa 1965).
1: 0–0.5%, 2: 0.5–1.0%, 3: 1.0–2.0%, 4: 2.0–5.0%, 5: 5.0–10.0%, 6: > 10%,
7: Ice age maximum glaciation
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Journal of Resources and Ecology Vol.2 No.2, 2011
2 Overview of the research
The beginnings of limnological studies in Poland can
be traced back to 1802–1805, when Polish researcher
Stanisław Staszic carried out preliminary studies on lakes
in the Tatra Mountains in the southern part of the country.
In the 1930s cartographers of the Military Institute of
Geography in Warsaw drew their bathymetric plans
(Choiński 2006–2007). Galon (1954) and Kalinowska
(1961) first paid attention to the processes of disappearance
of lakes in Poland. Tomaszewski (1974) analysed the
influence of vegetation and overgrowing processes, while
Babiński (1988) of drainage works on shrinkage of lakes
in the Great Poland Lowland. Glazik (1988), Superson and
Szwajgier (2003), Marszelewski and Adamczyk (2004) as
well as Choiński (2009) studied natural and anthropogenic
caused leading to changes in the area of lakes and wetlands
in selected parts of Northern Poland. In turn, Borowiak
(2002) pointed out the role of rock debris in morphometric
changes of lakes in the Polish Tatra Mountains.
that phenomenon in the years 1960–1975 is shown in Fig.
3.
4 Causes of changes in lake area
Causes of the detected changes should be seen both in
natural factors and human activity.
3 Changes in lake area in Poland
Lakes in Poland cover nearly 281 000 ha, that is
approximately 0.9% of the country’s area (Choiński 2006)
and they are located mainly (95.9%) in its northern part,
forming three geographical regions (lake districts): the
Pomeranian Lake District, the Masurian Lake District and
the Great Poland-Kuyavian Lake District (Table 1, Fig. 2).
Generally, lakes in Poland show the tendency to
decrease both in area and number. On the basis of analysed
all Polish lakes with an area ≥ 1 ha (as of 1975), Choiński
(2006) defined the scope of these changes. The data were
compared with the Catalogue of lakes in Poland (1954),
containing, among others, the area of lakes measured in
the 1920s: over that period the total area has shrunk from
316 614 ha to 280 977 ha (11.62%), while the number of
lakes decreased from 9296 to 7081 (23.82%). Within the
separated three lake districts these changes proceed at
different rate: between 1920 and 1975 the largest decline
in the surface area of lakes was observed in the Great
Poland-Kuyavian Lake District (11.62%), then (9.98%) in
the Masurian Lake District, while the lowest (9.69%) in
the Pomeranian Lake District. The spatial distribution of
Fig. 2 Distribution of lakes in Poland per 100 km2 of area [in %]
(after Majdanowski 1954).
decrease by 0%–5%
decrease by 5%–10%
decrease > 10%
growth areas
water divides of the 1st rank
lake district boundary
Fig. 3 Changes in lake area in Poland in 1960-1975 (after
Choiński 2007).
A: the Pomeranian Lake District, B: the Masurian Lake District,
C: the Great Poland-Kuyavian Lake District
Table 1 Basic data on lake districts in Poland.
Lake district
Pomeranian
Masurian
2
Area (km )
Lake coverage (%)
Number of lakes
Total area of lakes (ha)
Total capacity of lakes (km3)
*: Including area not covered by last glaciation.
Source: Choiński 2006.
51 340
2.03
3385
104 219.4
7.1
42 781
3.05
2061
130 481.0
10.1
Great Poland-
-Kuyavian
Poland*
34 190
1.23
1347
42 053.1
2.3
312 683
0.90
7081
280 977.0
19.7
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Adam Choiński, et al.: Causes of Lake Area Changes in Poland
Among natural factors the most important role play:
climate fluctuations, water inflow and the associated
sedimentation of clastic debris, depth of lake basins,
biomass growth, chemical precipitation, deforestation
caused by pests, and also local factors influencing the
incorporation of lakes into the hydrographic network.
In turn, the most important anthropogenic factors are:
deforestation, hydrotechnical works (including drainage),
intensity of agriculture and wastewater discharges within
the lake catchment that affect the lake eutrophy.
Some regularities of climate change have been observed
over centuries. They are determined by astrophysical
processes occurring in cycles; it can be concluded that
those changes take the form of sine, as for example
the sunspots with the 11-year cycles, which affect the
distribution of rainfall and temperature.
Water inflow plays one of the most important roles
in the process of changes in lake area. Main sources of
water input include: precipitation onto the lake surface,
runoff carried by rivers, surface and groundwater flows.
Precipitation is the primary factor. The average annual
precipitation in Poland is about 600 mm per year, however,
its spatial distribution is not uniform: the lowest values for
the analysed lake districts are recorded in their southern
part (500 mm per year), which is the area of the largest
water deficit in Poland. In the Great Poland-Kuyavian
Lake District, where the fastest decrease of lake area is
observed, the average amount of precipitation is 530 mm
per year (Table 2). Unfavorable water balance in the Great
Poland-Kuyavian Lake District is additionally enhanced
by high evaporation from the water surface. According
to Jurak (1987), who determined its average values for
Poland, the most intense evaporation (580–600 mm) is
in the central part of the country, including a large part
of the above-mentioned lake district. Consequently, the
volume of the direct precipitation onto the lake is there
much lower than the losses caused by evaporation from
the lake surface. In other parts of Poland the vertical
water exchange is at least balanced or there is a surplus on
the revenue side: for example, in the coastal regions the
annual average rainfall is about 650 mm, while the annual
average evaporation is around 550 mm. Moreover, studies
on climate change carried out by Boryczka (1998) show
that in the first half of the 21st century the annual average
precipitation in Poland will remain at similar level, yet, it
will be accompanied by increasing average temperatures,
that in turn will accelerate evaporation. An increasing trend
of air temperature has been already recorded for instance
at Poznań station (1.1℃ per 100 years), Kraków station
(1827–1997) (0.8℃ per 100 years) and Warsaw station
(1779–1990) (0.66℃ per 100 years).
Lange (1993) states that the longevity of a lake basin is
proportional to the share of parts relatively isolated from
the lake surface. As a result, the slowest pace of changes
is typical for deep lakes with high share of hypolimnion.
That relationship can be described by the average depth
of the lake, which determines, among others, how quickly
the plant succession may proceed. This means that the lake
is shallower, the sooner the succession proceeds, leading
to shrinkage of the lake basin. Consequently, the biomass
growth is also accelerated. Among the investigated lake
districts, the lowest value of the average depth, observed
in the Great Poland-Kuyavian Lake District, is the result
of the long-lasting levelling processes, since that area
was at the earliest revealed by the Scandinavian ice
sheet. Ptak (2010) defined statistical relationship between
the disappearance of the lakes and their average depth.
According to his calculations, the correlation coefficient
for 562 lakes in Poland in the many years’ period 19602000 is –0.22; the minus sign indicates that the degree
of lake area reduction is inversely proportional to their
average depth.
The rate of changes of the lake area is also determined
by lake openness. That parameter has a threefold
significance: it influences the degree of water level
oscillations, the supply of debris and the volume of
primary production responsible for the deposition of
nutrients. Open lakes in Poland have relatively small
Table 2 Selected natural and anthropogenic factors influencing changes of lake area in Poland.
Lake District
Factor
Pomeranian
Masurian
Precipitation1) (mm)
Average lake depth (m)
Percentage of open lakes (%)
Forests (%)
Consumption of fertilizers2) (kg ha-1)
Discharge of fertilizers into surface water2) (106m3)
600
6.84
37.1
33.2
221.1
2414.6
1) Average values for 1971–2000;
2) Average values for 1979–1983, based on: the Statistica Yearbook of Voivodeships 1980–1984.
Source: Own calculations.
585
7.45
44.8
16.0
180.5
422.2
Great Poland
-Kuyavian
530
5.70
56.0
23.3
232.5
2331.5
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Journal of Resources and Ecology Vol.2 No.2, 2011
fluctuations of water level (up to 50 cm). The amplitudes
are higher for other types of lakes and may even exceed
100 cm. Open lakes are recipients of both autochthonic
and allochthonic matter. There is a relationship: the higher
the percentage of open lakes, the faster disappearance of
lakes (the Great Poland-Kuyavian Lake District – 56.0%,
the Pomeranian Lake District – 37.1%).
Lakes are also producers of biomass within their own
basins. The volume of the biomass production depends on
the eutrophic type of the individual lake. The accumulation
of allochthonic and autochthonic material results in
shallowing and the ultimate disappearance of lakes. This
can be clearly seen in particular in shallow bays, which in
a relatively short time become “asylums” for new plant
species. These parts of the lake basin quickly change into
land, significantly reducing the area of the lake. Such a
situation has been observed in the Kaliszańskie Lake (Fig.
4) located in the Great Poland-Kuyavian Lake District. The
lake is surrounded by fields — a typical land use pattern
of the lake districts in Poland. Between 1890 and 2000 the
shallowing of the bay and the subsequent plant succession
in the southern part of that lake resulted in the reduction of
its area by 17.4%. Assuming the continuation of that trend,
the complete disappearance of the Kaliszańskie Lake may
occur within about 500 years. It has to be noted that the
pace of the lake basin shallowing may be several times
higher than the changes in the lake area (Choiński and Ptak
2009).
Besides natural factors, human activity plays an
increasing role in changes in lake area in Poland. The
beginnings of growing human impact can be associated
with the transition from the nomadic-hunting to the
agricultural lifestyle and the related changes in the
environment through deforestation, development of fields,
etc. Along with those changes a number of unintended
processes, derived from actions initiated earlier took place.
Human impact on the environment, originally marginal,
with each epoch (bronze, iron, steam engine) began
gaining momentum. Also the approach of man himself to
those actions changed: they become deliberate and precise
(draining of wetlands, damming of rivers and other). Man
became a new source of environmental changes, including
those in lakes.
Two lakes: Włókna and Brzeźno, located in the Great
Poland-Kuyavian Lake District may serve as a good
example of the result of human interference in water
relations. Due to construction of fish breeding ponds on
the nearby Mała Wełna River the water level of the lakes
between 1888 and 1998 fell by more than 1 m, while
their total area decreased by over 20%. This led to the
separation of one body of water from another and changes
in the course of the coastline (Fig. 5).
The most visible through the centuries is the reduction
of forest areas. Studies carried out by Gutry-Korycka
(1993) show that from the 10th to the mid-20th century
the forest area in Poland decreased by about 60%. Yet at
the end of the 18th century forests occupied about 38%
of the territory of Poland, while now about 28%. Water
circulation within the forest is similar to the natural,
undisturbed by man. Hence, from the hydrological point
of view, it is important that the watershed had possibly the
highest percentage of forest area. In the light of these data,
the most favourable conditions are in the Pomeranian Lake
District (33.2%), where the relatively lowest percentage of
disappearing lakes (9.69%) has been recorded.
Hydrotechnical works are another very important
Fig. 4 Changes in the shoreline of the Kaliszańskie Lake
(52°53′09″N, 17°07′46″E) between 1890 and 2000 (black
indicates the extent of the water surface reduction).
Fig. 5 The division of one reservoir into two separate lakes as
a result of reduction of the lake area between 1888 and 1998
(52°38′52″N, 17°06′51″E). Photo: M. Ptak.
179
Adam Choiński, et al.: Causes of Lake Area Changes in Poland
factor influencing changes in lake area in Poland.
While the creation of reservoirs has a positive effect on
the phenomenon in question, the regulation of rivers
significantly accelerates the disappearance of lakes. The
most often implemented in Poland hydrotechnical works
consisted of straightening of the river channels for shipping,
which accelerated the outflow from the watershed. Increase
in the longitudinal fall of rivers accelerated the outflow of
water from open lakes, which resulted in the decrease of
their area (Kaniecki 1997).
Agricultural land improvement (amelioration) includes
measurements aimed to control water circulation in order
to use the area for agriculture. They are: collection of
water in reservoirs, drainage, etc. The first works on the
drainage of the Great Poland Lowland was started in
the late 18th century and ended in the mid-19th century
(Kaniecki 1991). As a result, the water level of Lake Gopło
was lowered by 2.7 m, while many, mainly smaller lakes
completely disappeared. In that way areas were converted
into grasslands.
At present agriculture plays a fundamental role in
the processes of disappearance of lakes in Poland.
Intensification of that sector of the economy, aiming at
an increase of productivity, enforces the use of synthetic
fertilizers, which through surface flow enrich surface water
in nutrients (nitrogen and phosphorus compounds). Equally
serious are the risks posed by wastewater discharges, both
industrial and municipal. As a result, an adverse eutrophic
growth (eutrophication) is observed. Eutrophication is a
natural process, however, in recent decades it has been
greatly intensified by human activity (Fig. 6).
The major adverse effects of eutrophication include
reduction in water transparency and algal blooms
contributing to the extinction of aquatic life and the
Table 3 Tolerable and dangerous loads of nitrogen and
phosphorus.
Average lake
depth (m)
5
10
50
100
150
200
Load (g m-1 y-1)
Tolerable
N
1.0
1.5
4.0
6.0
7.5
9.0
P
0.007
0.10
0.25
0.40
0.50
0.60
Dangerous
N
2.0
3.0
8.0
12.0
15.0
18.0
P
0.13
0.20
0.50
0.80
1.00
1.20
Source: Kajak 2001.
formation of oxygen deficits (including the total lack of
oxygen).
Kajak (2001) on the basis of research on eutrophication
on a global scale defined the approximate amounts of
eutrophying substances, which pose no threat to the
lake (i.e. lake is able to neutralize them). The data are
summarized in Table 3.
Release of 1 kg of phosphorus into water increases the
weight of the plankton by 1 ton (Kajak 1979). This process
initiates a drastic acceleration of the biomass growth
in the reservoir, which in turn leads to an accelerated
growth of lake deposits and results in shallowing and
eventual disappearance (terrestialisation) of the lake basin.
Therefore, reduction in the inflow of the nutrients into the
lake would have resulted in the slowdown of the abovementioned changes.
Churski (1993) concludes that at present human activity
poses serious threat to all lakes in Poland, especially
shallow and polymictic ones located in the agricultural and
built-up zones. It should be noted that despite initiated in
Poland in the 1990s economic transition and the associated
significant reduction of human influence on the lakes
(reflected in decrease in quantity of wastewater discharged
into the lakes and used fertilizers), a negative process of
disappearance of lakes is still observed, as it has been
proved by the results of studies on individual lakes and
their groups. The main reason of these changes is a huge
amount of nutrients deposited in the sediments. They are a
source of internal ‘feeding’, which will remain active for
the next dozen or even several dozen years.
5 Summary
Fig. 6 The increase in eutrophy of water as a result of growth
(on a global scale) of quantity of the total phosphorus loads to
water (Σ) (after Kajak 2001).
N.a.: natural area sources; A.a.: anthropogenic area sources;
A.p.: anthropogenic point sources
Disappearance of lakes is a very complex process that
depends on a number of overlapping factors; these
outlined in the paper refer to the separated at the macro
scale geographical regions (lake districts) in Poland. Since
the response of every lake to the changes in its catchment
is different, detailed studies on causes of that phenomenon
should be carried out at a scale of individual lake basins
and their catchments. However, such studies would be
180
Journal of Resources and Ecology Vol.2 No.2, 2011
complicated and time-consuming. Consequently, at the
initial stage of the research information on the driving
forces of the observed changes should be obtained.
Finally, in has to be mentioned that over the last few
years a number of measures have been taken to slow down
the process of disappearance of lakes in Poland. Examples
include programs launched by the local authorities, aiming
to protect lakeshores and reduce eutrophication through
improvement of water quality. Further actions should also
focus on the inhabitants in order to raise their awareness of
human impact on the lakes.
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波兰湖泊面积变化因素
Adam CHOIŃSKI1, Agnieszka ŁAWNICZAK2, Mariusz PTAK1, Leszek SOBKOWIAK1
1 亚当密茨凯维奇大学自然地理与环境规划研究所，波兹南61-680，波兰；
2 波兹南大学生命科学学院生态学与农业环境保护研究室，波兹南60-649，波兰；
摘要：波兰北部有众多斯堪的纳维亚冰盖冰期形成的湖泊。通过湖泊区的研究，发现湖泊面积在逐渐减少，甚至导致消失。
本文对变化的程度进行了观测，指出影响波兰湖泊面积变化的主要自然与人为因素，包括气候变化、湖盆深度、生物量增长、森
林砍伐、水利工程建修、农药利用和排污等。
关键词：波兰北部；湖泊地区；湖泊面积变化；自然因素；人为因素