Geoscience Reference
In-Depth Information
Subsequently, the following studies were carried out:
l
Thermal regime of the lake under the influence of heated water discharge
l
Possible hazard to the nuclear power plant resulting from a breakdown of the
upper reservoir of the pumped-storage power plant
In this chapter, special attention will be directed to thermal regime of the lake,
which is very important for hydro-chemical and hydro-biological state of the lake
in natural conditions but also with the operation of nuclear plant. An important
problem was the water balance of the lake taking into account additional evapora-
tion caused by heated water discharge from the nuclear plant.
2 General Information on the Lake
˙
arnowiec
Lake
˙
arnowiec is of glacial origin; it is situated in the Pia´nica River valley
between two forest grown moraine hills elevated more than 100 m above the lake
water level. The average water surface of the lake is 14.30 km
2
, and the volume is
120 hm
3
. The length of the lake is 7.6 km, and the maximum width is 2.6 km. The
maximum water depth is 19.4 m, and the average depth is 8.4 m.
In natural conditions, average water level is 1.34 m above sea level (asl). The
minimum observed water surface level was 0.92 m asl, and the maximum was
1.78 m asl. The residence time of the inflow to the lake is about 1.7 years. During
vegetation season, water was abstracted from the lake to irrigate meadows situated
north from the lake. Wind induced currents in the lake are of the order 0.1 m/s.
Wind generated waves reach a height of 0.5-0.6 m. During winter, the lake is
covered with ice, which may achieve a thickness of 0.5 m. Maximum number of
days with ice on the lake was 133, and the average was about 80 (Majewski
1983
).
There are two surface inflows to the lake and one outflow directly to the sea. The
total surface inflow to the lake is estimated at 1.6 m
3
/s. Because high moraine hills
are situated on both sides of the lake, there is a significant inflow of ground water to
the lake, which is estimated as 0.6 m
3
/s. Outflow from the lake to the sea is in
natural form and its value changes with water level in the lake.
3 Catchment of the Lake
The catchment of the lake is 249 km
2
and belongs to the catchment of Pia´nica
River (310 km
2
). Lake catchment consists of the catchment of Pia´nica G´rna
(88 km
2
), catchment of the Bychowska Struga (122 km
2
), and direct catchment of
the lake (39 km
2
). The length of Pia´nica G´rna is 16.7 km with the average slope
3.3
.
The catchment of the Lower Pia´nica has the surface of 61 km
2
. The catchment
of the lake is occupied by agricultural land, meadows, forests, and wasteland.
, and the length of Bychowska Struga is 20.1 km with average slope of 2.2
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