5 Water Resources of Stagnant Waters
65
Fig. 5.1 Variability of the retention index of lake waters (mm): 1 – below 50, 2 – 50–100, 3
– 100–250, 4 – 250–500, 5 – above 500, 6 – delineated the range of the last glaciation
Figure 5.1 presents regional variability of water resources of lakes expressed as
the retention index in mm. The map of retention capacities was prepared based on
the outlines of maps at a scale of 1:50,000 for more than 200 sheets of topographic
maps. The middle of each field was ascribed a retention value providing the basis for
interpolation. Retention capacity was expressed in mm, permitting its comparison
with other indices. The determined retention capacity for the area north of the line
delimiting the maximum range of the last glaciation is 162 mm. An evident two-fold
character of the analysed phenomenon is observed on the map, i.e. the Masurian and
Pomeranian Lake District have considerably larger resources than the WielkopolskaKujawy Lake District. The zone of maximum resources has an evident latitudinal
orientation and reaches the highest values, usually south of the I degree watershed,
both in the case of the Pomeranian and Masurian Lakelands. Based on delineation of
[3], the greatest resources within the Masurian Lake District occur in the following
catchments: W˛ egorapa (404 A) – 1976 mm, Biała Ha´ ncza (407) – 958 mm, and
Pisa (227 A) – 893 mm, and in the Pomeranian Lake District in catchments of:
Drawa (119 D) – 389 mm, Wda (237 B) – 196 mm, and in the Przymorze catchment
from Wieprza to Słupia (310) – 184 mm. Within the Wielkopolska-Kujawy Lake
District, lake catchments retain considerably less waters, and the most abundant
ones include Vistula from Bzura to Skrwa (233 A) – 173 mm, Warta from Wełna to
Obra (118 G) – 141 mm, and Note´ c to Gwda (119 A) – 116 mm. Zones with the
lowest retention capacity, i.e. up to 50 mm, are located in valleys of the largest rivers
with the adjacent areas, and coasts: Gda´ nsk, East Baltic, Szczecin, and the southern
part of the Koszalin Coast. Mean retention capacity determined within the three lake
districts is exceptionally variable. In the case of the Masurian Lake District, it is
283 mm, for the Pomeranian Lake District the index equals 150 mm, and for the
Wielkopolska-Kujawy Lake District only 58 mm. The division of the total volume
65
Fig. 5.1 Variability of the retention index of lake waters (mm): 1 – below 50, 2 – 50–100, 3
– 100–250, 4 – 250–500, 5 – above 500, 6 – delineated the range of the last glaciation
Figure 5.1 presents regional variability of water resources of lakes expressed as
the retention index in mm. The map of retention capacities was prepared based on
the outlines of maps at a scale of 1:50,000 for more than 200 sheets of topographic
maps. The middle of each field was ascribed a retention value providing the basis for
interpolation. Retention capacity was expressed in mm, permitting its comparison
with other indices. The determined retention capacity for the area north of the line
delimiting the maximum range of the last glaciation is 162 mm. An evident two-fold
character of the analysed phenomenon is observed on the map, i.e. the Masurian and
Pomeranian Lake District have considerably larger resources than the WielkopolskaKujawy Lake District. The zone of maximum resources has an evident latitudinal
orientation and reaches the highest values, usually south of the I degree watershed,
both in the case of the Pomeranian and Masurian Lakelands. Based on delineation of
[3], the greatest resources within the Masurian Lake District occur in the following
catchments: W˛ egorapa (404 A) – 1976 mm, Biała Ha´ ncza (407) – 958 mm, and
Pisa (227 A) – 893 mm, and in the Pomeranian Lake District in catchments of:
Drawa (119 D) – 389 mm, Wda (237 B) – 196 mm, and in the Przymorze catchment
from Wieprza to Słupia (310) – 184 mm. Within the Wielkopolska-Kujawy Lake
District, lake catchments retain considerably less waters, and the most abundant
ones include Vistula from Bzura to Skrwa (233 A) – 173 mm, Warta from Wełna to
Obra (118 G) – 141 mm, and Note´ c to Gwda (119 A) – 116 mm. Zones with the
lowest retention capacity, i.e. up to 50 mm, are located in valleys of the largest rivers
with the adjacent areas, and coasts: Gda´ nsk, East Baltic, Szczecin, and the southern
part of the Koszalin Coast. Mean retention capacity determined within the three lake
districts is exceptionally variable. In the case of the Masurian Lake District, it is
283 mm, for the Pomeranian Lake District the index equals 150 mm, and for the
Wielkopolska-Kujawy Lake District only 58 mm. The division of the total volume