196
P. Jokiel and P. Tomalski
from large mountain rivers including the Kaczawa (between Malczyce and ´
Scinawa),
which slightly enhance the seasonality, and lowland rivers including the Barycz
(between ´
Scinawa and Cigacice), which exert contrary effects. Interestingly, the
entrances of the Bóbr (between Cigacice and Poł˛ eka) and the Nysa Łu˙ zycka (between
Poł˛ ecko and Słubice) do not cause major changes in the seasonal nature of the Oder
flow. No significant changes in the Oder seasonality are observed downstream of
the Warta entrance, similarly as for the Narew entrance into the Vistula. The index
and coefficient of seasonality (IS and GMO) in Gozdowice and Widuchowa are only
slightly lower than in Słubice although the Oder basin area more than doubles along
this section (Table 10.2, Fig. 10.5). This clearly shows that the Oder flow regime,
and particularly seasonality at Słubice are similar to that at the mouth of the Warta.
The longer the Oder and the larger its basin, the earlier the concentration date
and half-flow date fall. In the upper section of the river PK and TPO reach 180–
185 and 170–175 days, respectively. In the lower section, they drop to 150–155 and
162–163 days. This fall is not smooth, and the spread of its values is slightly larger
(especially in the middle section) than for the Vistula. Between Racibórz-Miedonia
and ´
Scinawa both parameters indicate relatively late PK and TPO, and downstream
both dates fall rather early in the year (Fig. 10.5). This delay in PK and TPO is
clearly due to a significant supply of water from water-rich mountain rivers (the
Nysa Kłodzka, the Kaczawa and a few others), while the acceleration downstream
results from the entrance of many lowland rivers, mainly the Barycz. Regression
models of the relationships between TPO and PK and A o and L o are statistically
significant but burdened with large regression errors, similarly as for the Vistula.
The relationships between the concentration date (PK) and half-flow date (TPO)
with the Oder basin are, like for the Vistula, slightly stronger than the correlation of
these parameters with the river length.
The equations presented above allow for assessing the rate of PK and TPO drop
associated with increasing basin area and length of both rivers (Figs. 10.4 and 10.5).
An increase in the Vistula and the Oder catchment area by 1000 km
2 causes the same
acceleration of half-flow date by on average one day. As for the concentration date,
the acceleration for the Oder is clearly greater and reaches three days per 1000 km
2 ,
while for the Vistula it is one day. This dependency is even more complex when
we consider the length of both rivers. An increase in the Vistula length by 100 km
accelerates PK by three days and TPO by over two days. For the Oder, average
gradients reach slightly over three days and about one and a half day, respectively.
10.6 Multiannual Fluctuations in Flow Seasonality
Our assessment of long-term changes and fluctuations in the scale, directions and
covariability of various aspects of flow seasonality in the two largest Polish rivers (the
Vistula and the Oder) is based on the data obtained for the following water gauges:
Jagodniki, Warsaw and Tczew (the Vistula) and ´
Scinawa, Poł˛ ecko and Gozdowice
(the Oder). The analysis of various seasonality parameters along the course of both
P. Jokiel and P. Tomalski
from large mountain rivers including the Kaczawa (between Malczyce and ´
Scinawa),
which slightly enhance the seasonality, and lowland rivers including the Barycz
(between ´
Scinawa and Cigacice), which exert contrary effects. Interestingly, the
entrances of the Bóbr (between Cigacice and Poł˛ eka) and the Nysa Łu˙ zycka (between
Poł˛ ecko and Słubice) do not cause major changes in the seasonal nature of the Oder
flow. No significant changes in the Oder seasonality are observed downstream of
the Warta entrance, similarly as for the Narew entrance into the Vistula. The index
and coefficient of seasonality (IS and GMO) in Gozdowice and Widuchowa are only
slightly lower than in Słubice although the Oder basin area more than doubles along
this section (Table 10.2, Fig. 10.5). This clearly shows that the Oder flow regime,
and particularly seasonality at Słubice are similar to that at the mouth of the Warta.
The longer the Oder and the larger its basin, the earlier the concentration date
and half-flow date fall. In the upper section of the river PK and TPO reach 180–
185 and 170–175 days, respectively. In the lower section, they drop to 150–155 and
162–163 days. This fall is not smooth, and the spread of its values is slightly larger
(especially in the middle section) than for the Vistula. Between Racibórz-Miedonia
and ´
Scinawa both parameters indicate relatively late PK and TPO, and downstream
both dates fall rather early in the year (Fig. 10.5). This delay in PK and TPO is
clearly due to a significant supply of water from water-rich mountain rivers (the
Nysa Kłodzka, the Kaczawa and a few others), while the acceleration downstream
results from the entrance of many lowland rivers, mainly the Barycz. Regression
models of the relationships between TPO and PK and A o and L o are statistically
significant but burdened with large regression errors, similarly as for the Vistula.
The relationships between the concentration date (PK) and half-flow date (TPO)
with the Oder basin are, like for the Vistula, slightly stronger than the correlation of
these parameters with the river length.
The equations presented above allow for assessing the rate of PK and TPO drop
associated with increasing basin area and length of both rivers (Figs. 10.4 and 10.5).
An increase in the Vistula and the Oder catchment area by 1000 km
2 causes the same
acceleration of half-flow date by on average one day. As for the concentration date,
the acceleration for the Oder is clearly greater and reaches three days per 1000 km
2 ,
while for the Vistula it is one day. This dependency is even more complex when
we consider the length of both rivers. An increase in the Vistula length by 100 km
accelerates PK by three days and TPO by over two days. For the Oder, average
gradients reach slightly over three days and about one and a half day, respectively.
10.6 Multiannual Fluctuations in Flow Seasonality
Our assessment of long-term changes and fluctuations in the scale, directions and
covariability of various aspects of flow seasonality in the two largest Polish rivers (the
Vistula and the Oder) is based on the data obtained for the following water gauges:
Jagodniki, Warsaw and Tczew (the Vistula) and ´
Scinawa, Poł˛ ecko and Gozdowice
(the Oder). The analysis of various seasonality parameters along the course of both