52
Z. Michalczyk and J. Sposób
dm
3 ·s
−1 ·km
−2 . In the Masurian Lake District, they increase to 6 dm
3 ·s
−1 ·km
−2 , and
in the Pomeranian Lake District to 10 dm
3 ·s
−1 ·km
−2 . In the zone of uplands, values
of unitary outflows consequently increase with height from 4 to 8 dm
3 ·s
−1 ·km
−2 . In
the Carpathian Foothills, Carpathians, and Sudeten Foothills and Sudeten, outflow
increases with height, from 6 dm
3 ·s
−1 ·km
−2 in the boundary zone of the mountain
area to 15–30 dm
3 ·s
−1 ·km
−2 in the Carpathians and Sudeten. In the Tatra Mountains,
mean unitary outflow exceeds 40 dm
3 ·s
−1 ·km
−2 .
In the southern part of Poland, the height of the outflow layer increases with
land elevation as a consequence of an increase in atmospheric precipitation in the
mountains. In the Tatra Mountains, the annual outflow layer exceeds 1000 mm, in the
Carpathians and Sudeten it equals 300–500 mm. In the zone of Uplands of Central
Poland, the outflow layer is 150–220 mm. It is somewhat higher in the Lake District,
where it exceeds even 300 mm. The lowest outflow, below 100 mm, is observed in
the zone of Lowlands of Central Poland, and in some of its parts, it does not even
reach 70 mm (part of Kujawy and central Wielkopolska).
The value of river discharge, mainly dependent on the amount of atmospheric
precipitation and the surface area of the catchment, changes seasonally, which is
directly related to the type of alimentation of rivers. Outside the mountain area, the
highest discharges occur in spring as a result of the release of water retained in the
snow cover. In the mountains, the highest river discharges occur during intensive
rainfalls at the beginning of summer. High variability of discharges in rivers makes
it challenging to manage the entire mass of outflowing water, and causes problems
with water excess or deficits. A particularly difficult situation occurs both during
flood flows and low flows. In the remaining period, rivers are relatively evenly fed
from the groundwater resources. Discharges of the largest Polish rivers in their mouth
sections, together with the length of the rivers and size of their catchment areas, are
presented in Table 4.2. Polish rivers with the most abundant water resources are the
Vistula and Oder Rivers, and their tributaries, namely Narew and Warta.
Atmospheric waters are retained in rocks, lakes, ponds, and reservoirs, and part
of them flows directly to rivers. The amount of groundwater resources is mainly
determined by natural conditions: the amount of atmospheric precipitation, type of
rocks and land relief, soil permeability, and retention capacity of the catchment,
as well as anthropogenic factors: water bodies, meliorations and river regulation,
urbanisation, and the related change of land use structure and others. The distribution
of groundwater resources in the territory of Poland refers to conditions resulting from
the geological structure, and particularly the range and thickness of aquifers and their
water capacity. Water resources of a given area can occur in rocks of different ages,
and be renewed through infiltration of precipitation waters. The exploitable resources
of the main aquifers occurring in the territory of Poland and their area of occurrence
are presented in Table 4.3.
In the territory of Poland, groundwaters of the first aquifer occur in rocks of
different ages. The largest area is occupied by waters of the Quaternary aquifer
the resources of which exist over 75% of the area of the country (Table 4.3), and
collect 51% of exploitable resources. Over a somewhat smaller area, often underlying
Quaternary deposits, wet rocks of the Palaeogene and Neogene occur (61%). Wet
Z. Michalczyk and J. Sposób
dm
3 ·s
−1 ·km
−2 . In the Masurian Lake District, they increase to 6 dm
3 ·s
−1 ·km
−2 , and
in the Pomeranian Lake District to 10 dm
3 ·s
−1 ·km
−2 . In the zone of uplands, values
of unitary outflows consequently increase with height from 4 to 8 dm
3 ·s
−1 ·km
−2 . In
the Carpathian Foothills, Carpathians, and Sudeten Foothills and Sudeten, outflow
increases with height, from 6 dm
3 ·s
−1 ·km
−2 in the boundary zone of the mountain
area to 15–30 dm
3 ·s
−1 ·km
−2 in the Carpathians and Sudeten. In the Tatra Mountains,
mean unitary outflow exceeds 40 dm
3 ·s
−1 ·km
−2 .
In the southern part of Poland, the height of the outflow layer increases with
land elevation as a consequence of an increase in atmospheric precipitation in the
mountains. In the Tatra Mountains, the annual outflow layer exceeds 1000 mm, in the
Carpathians and Sudeten it equals 300–500 mm. In the zone of Uplands of Central
Poland, the outflow layer is 150–220 mm. It is somewhat higher in the Lake District,
where it exceeds even 300 mm. The lowest outflow, below 100 mm, is observed in
the zone of Lowlands of Central Poland, and in some of its parts, it does not even
reach 70 mm (part of Kujawy and central Wielkopolska).
The value of river discharge, mainly dependent on the amount of atmospheric
precipitation and the surface area of the catchment, changes seasonally, which is
directly related to the type of alimentation of rivers. Outside the mountain area, the
highest discharges occur in spring as a result of the release of water retained in the
snow cover. In the mountains, the highest river discharges occur during intensive
rainfalls at the beginning of summer. High variability of discharges in rivers makes
it challenging to manage the entire mass of outflowing water, and causes problems
with water excess or deficits. A particularly difficult situation occurs both during
flood flows and low flows. In the remaining period, rivers are relatively evenly fed
from the groundwater resources. Discharges of the largest Polish rivers in their mouth
sections, together with the length of the rivers and size of their catchment areas, are
presented in Table 4.2. Polish rivers with the most abundant water resources are the
Vistula and Oder Rivers, and their tributaries, namely Narew and Warta.
Atmospheric waters are retained in rocks, lakes, ponds, and reservoirs, and part
of them flows directly to rivers. The amount of groundwater resources is mainly
determined by natural conditions: the amount of atmospheric precipitation, type of
rocks and land relief, soil permeability, and retention capacity of the catchment,
as well as anthropogenic factors: water bodies, meliorations and river regulation,
urbanisation, and the related change of land use structure and others. The distribution
of groundwater resources in the territory of Poland refers to conditions resulting from
the geological structure, and particularly the range and thickness of aquifers and their
water capacity. Water resources of a given area can occur in rocks of different ages,
and be renewed through infiltration of precipitation waters. The exploitable resources
of the main aquifers occurring in the territory of Poland and their area of occurrence
are presented in Table 4.3.
In the territory of Poland, groundwaters of the first aquifer occur in rocks of
different ages. The largest area is occupied by waters of the Quaternary aquifer
the resources of which exist over 75% of the area of the country (Table 4.3), and
collect 51% of exploitable resources. Over a somewhat smaller area, often underlying
Quaternary deposits, wet rocks of the Palaeogene and Neogene occur (61%). Wet