10 Flow Seasonality in Two Big Polish Rivers – The Vistula …
185
show high spatial diversity – they are moderate in the upper (upland) section, small
in the middle and lower (lowland) section, to very small locally [18]. Together with
the Warta catchment, the central part of the Oder basin covers an area of 99,018 km
2 .
The rivers in this part of the basin have diverse regimes. The left tributaries fed from
Sudeten springs have nival-pluvial or locally pluvial-nival regimes, while lowland
right and some left tributaries have moderately or locally strongly developed nival
regime [25].
The Lower Oder is a lowland, engineered river widely used for navigation. Its
lower section is 144.3 km long, and its basin covers 10,796 km
2 (7,221 km
2 in
Poland). The watercourses entering the Oder from Poland include the My´ sla, the
Rurzyca, the Płonia (via D˛ abie Lake) and the Ina, and from Germany the Finowkanal
and the Weise. These watercourses have moderately developed nival regime. Polish
rivers typically feature a high share of underground water supply, while the flows
in the watercourses entering the Oder from Germany depend on the needs for
draining some sections of old Oder beds and requirements of navigation within
E70 waterway. Mean multiannual flow of the Oder slightly above its mouth (Widuchowa water gauge) is SSQ (multiannual mean flow) = 534.6 m
3. s
−1 (1974–2013),
while the maximum and minimum flows reached WWQ (multiannual high flow) =
2980 m
3. s
−1 (August 1997) and NNQ (multiannual low flow) = 153 m
3. s
−1 (August
1992), respectively. Interestingly, both extreme flows occurred in the same month.
10.3 Physical and Geographical Conditions of Flow
Seasonality in Polish Rivers
The hydrological effects triggered by increased area and physiographic diversity of
a catchment are well known among hydrologists. They generally affect the flow
regime in qualitative and quantitative terms and change the character of the river
and its valley. As the catchment area increases, medium and maximum unit flow is
usually reduced, and minimum flow rises. Therefore, flow variability drops and its
inertia grows as a consequence of elevated retention. In larger catchments, extreme
events (floods, low water) develop and cease more slowly and last longer than in
small catchments. Also, extreme flows less closely correlate with the onset of the
triggering factor. On top of all these, there are also effects caused by changes in
stationary and non-stationary conditions and factors of flow formation.
One of the features shaping the catchment flow regime is its seasonality. Information on seasonality of river flow is the most basic and most important in hydrological
practice and water management. The temporal regime of the river flow obviously
depends on seasonal diversity in abundance and type of precipitation and intensity of surface evaporation. However, apart from external (e.g. climatic) factors,
the flow is affected by a number of phenomena and processes associated with the
river and its catchment. The catchment and the river system form a set of filters in
which the external impulses (weather, climatic or anthropogenic) are so strongly
185
show high spatial diversity – they are moderate in the upper (upland) section, small
in the middle and lower (lowland) section, to very small locally [18]. Together with
the Warta catchment, the central part of the Oder basin covers an area of 99,018 km
2 .
The rivers in this part of the basin have diverse regimes. The left tributaries fed from
Sudeten springs have nival-pluvial or locally pluvial-nival regimes, while lowland
right and some left tributaries have moderately or locally strongly developed nival
regime [25].
The Lower Oder is a lowland, engineered river widely used for navigation. Its
lower section is 144.3 km long, and its basin covers 10,796 km
2 (7,221 km
2 in
Poland). The watercourses entering the Oder from Poland include the My´ sla, the
Rurzyca, the Płonia (via D˛ abie Lake) and the Ina, and from Germany the Finowkanal
and the Weise. These watercourses have moderately developed nival regime. Polish
rivers typically feature a high share of underground water supply, while the flows
in the watercourses entering the Oder from Germany depend on the needs for
draining some sections of old Oder beds and requirements of navigation within
E70 waterway. Mean multiannual flow of the Oder slightly above its mouth (Widuchowa water gauge) is SSQ (multiannual mean flow) = 534.6 m
3. s
−1 (1974–2013),
while the maximum and minimum flows reached WWQ (multiannual high flow) =
2980 m
3. s
−1 (August 1997) and NNQ (multiannual low flow) = 153 m
3. s
−1 (August
1992), respectively. Interestingly, both extreme flows occurred in the same month.
10.3 Physical and Geographical Conditions of Flow
Seasonality in Polish Rivers
The hydrological effects triggered by increased area and physiographic diversity of
a catchment are well known among hydrologists. They generally affect the flow
regime in qualitative and quantitative terms and change the character of the river
and its valley. As the catchment area increases, medium and maximum unit flow is
usually reduced, and minimum flow rises. Therefore, flow variability drops and its
inertia grows as a consequence of elevated retention. In larger catchments, extreme
events (floods, low water) develop and cease more slowly and last longer than in
small catchments. Also, extreme flows less closely correlate with the onset of the
triggering factor. On top of all these, there are also effects caused by changes in
stationary and non-stationary conditions and factors of flow formation.
One of the features shaping the catchment flow regime is its seasonality. Information on seasonality of river flow is the most basic and most important in hydrological
practice and water management. The temporal regime of the river flow obviously
depends on seasonal diversity in abundance and type of precipitation and intensity of surface evaporation. However, apart from external (e.g. climatic) factors,
the flow is affected by a number of phenomena and processes associated with the
river and its catchment. The catchment and the river system form a set of filters in
which the external impulses (weather, climatic or anthropogenic) are so strongly