15 Monitoring of Small Catchments in …
367
In 1994–2017 at Koniczynka the mean annual precipitation total was 543.1 mm.
Annual totals ranged from 405.0 mm (1996) to 762.0 mm (2001). In the annual
course, the highest total values of precipitation were recorded in the summer (July
93.0 mm), and the lowest in the winter (February 26.4 mm). In individual months,
the totals were quite varied: from 2.1 mm in January 1997 to 190.3 mm in July 2003.
There were 178.7 precipitation days (p ≥ 0.1 mm) in a year, including 96.0 days
with p ≥ 1.0 mm and 11.9 days with p ≥ 10.0 mm. No statistically significant trends
in precipitation were observed, but there were some series of wet and dry years
(Fig. 15.14). In the analysed years there were 15 meteorological droughts during
which there was no precipitation for at least 15 days in a row.
The snow cover at Koniczynka formed from early October to the end of April,
but its mean duration was only 29 days. Snow cover persisted the longest during the
winter of 2012/2013 (80 days). The average thickness of the snow was a few to a
dozen-or-so centimetres, but in 2010 it reached a record 40 cm. Winters without longterm snow cover have been increasingly observed, which has a significant influence
on the environmental water resources.
The water stages and flow rates in the Struga Toru´ nska are very variable and dependent on weather conditions. There is a clear dependence of the outflow from the atmospheric circulation associated with the North Atlantic Oscillation (NAO) phases [38].
The highest flow rates are observed in the spring. However, the water regime includes
numerous flow disturbances, surges, and lows connected with specific weather. The
river quickly responds to torrential rain, snow melting and atmospheric droughts due
primarily to anthropogenic transformations and man-made drainage of the catchment. This is particularly evident in periods of long-term high air temperatures,
which favour low flows and contribute to an increased soil moisture deficit. Moreover, the complex geology of the land affects water infiltration and retention [14].
The local drainage system and lack of forests limit the retention capacity of the
catchment. As a result, water stages are subject to rapid changes after precipitation
events because of quick surface runoff and drainage.
The mean specific runoff from the entire catchment of the Struga Toru´ nska to
Koniczynka in 1994–2017 was 1.76 dm
3 s
−1 km
−2 and was among the lowest in
Poland. However, in the separated representative catchment between Lipowiec and
Koniczynka, the specific runoff was much greater (5.60 dm
3 s
−1 km
−2 ) and typical
of Central Poland (5.4 dm
3 s
−1 km
−2 ). It was different again for different parts of
the catchment (ranging from less than 2.0 dm
3 s
−1 km
−2 to approx. 9.0 dm
3 s
−1
km
−2 ) and temporally varied [31, 35]. The smallest specific runoff in Poland is 2–4
dm
3 s
−1 km
−2 and occurs in the belt of Middle Polish Plains [31, 38]. For example,
the runoff from the agricultural catchment of the Zgłowi˛ aczka river in 1951–2012
was 2.51 dm
3 s
−1 km
−2 [39]. Similar values (2.1 dm
3 s
−1 km
−2 ) were observed in
the agricultural catchment of the Borucinka river in 2010 [40]. To compare, in the
catchments of mountainous tributaries of the Vistula, the runoff exceeds 12 dm
3 s
−1
km
−2 [39]. Jokiel and Stanisławczyk [41] stated that seasonal structures of runoff
undergo nearly parallel changes in neighbouring rivers, and are similar in the case
of rivers supplying the same regions. Water resources in Poland are small and do
367
In 1994–2017 at Koniczynka the mean annual precipitation total was 543.1 mm.
Annual totals ranged from 405.0 mm (1996) to 762.0 mm (2001). In the annual
course, the highest total values of precipitation were recorded in the summer (July
93.0 mm), and the lowest in the winter (February 26.4 mm). In individual months,
the totals were quite varied: from 2.1 mm in January 1997 to 190.3 mm in July 2003.
There were 178.7 precipitation days (p ≥ 0.1 mm) in a year, including 96.0 days
with p ≥ 1.0 mm and 11.9 days with p ≥ 10.0 mm. No statistically significant trends
in precipitation were observed, but there were some series of wet and dry years
(Fig. 15.14). In the analysed years there were 15 meteorological droughts during
which there was no precipitation for at least 15 days in a row.
The snow cover at Koniczynka formed from early October to the end of April,
but its mean duration was only 29 days. Snow cover persisted the longest during the
winter of 2012/2013 (80 days). The average thickness of the snow was a few to a
dozen-or-so centimetres, but in 2010 it reached a record 40 cm. Winters without longterm snow cover have been increasingly observed, which has a significant influence
on the environmental water resources.
The water stages and flow rates in the Struga Toru´ nska are very variable and dependent on weather conditions. There is a clear dependence of the outflow from the atmospheric circulation associated with the North Atlantic Oscillation (NAO) phases [38].
The highest flow rates are observed in the spring. However, the water regime includes
numerous flow disturbances, surges, and lows connected with specific weather. The
river quickly responds to torrential rain, snow melting and atmospheric droughts due
primarily to anthropogenic transformations and man-made drainage of the catchment. This is particularly evident in periods of long-term high air temperatures,
which favour low flows and contribute to an increased soil moisture deficit. Moreover, the complex geology of the land affects water infiltration and retention [14].
The local drainage system and lack of forests limit the retention capacity of the
catchment. As a result, water stages are subject to rapid changes after precipitation
events because of quick surface runoff and drainage.
The mean specific runoff from the entire catchment of the Struga Toru´ nska to
Koniczynka in 1994–2017 was 1.76 dm
3 s
−1 km
−2 and was among the lowest in
Poland. However, in the separated representative catchment between Lipowiec and
Koniczynka, the specific runoff was much greater (5.60 dm
3 s
−1 km
−2 ) and typical
of Central Poland (5.4 dm
3 s
−1 km
−2 ). It was different again for different parts of
the catchment (ranging from less than 2.0 dm
3 s
−1 km
−2 to approx. 9.0 dm
3 s
−1
km
−2 ) and temporally varied [31, 35]. The smallest specific runoff in Poland is 2–4
dm
3 s
−1 km
−2 and occurs in the belt of Middle Polish Plains [31, 38]. For example,
the runoff from the agricultural catchment of the Zgłowi˛ aczka river in 1951–2012
was 2.51 dm
3 s
−1 km
−2 [39]. Similar values (2.1 dm
3 s
−1 km
−2 ) were observed in
the agricultural catchment of the Borucinka river in 2010 [40]. To compare, in the
catchments of mountainous tributaries of the Vistula, the runoff exceeds 12 dm
3 s
−1
km
−2 [39]. Jokiel and Stanisławczyk [41] stated that seasonal structures of runoff
undergo nearly parallel changes in neighbouring rivers, and are similar in the case
of rivers supplying the same regions. Water resources in Poland are small and do