Regional differences in the influence of the North Atlantic Oscillation on seasonal river runoff in Poland

In this paper, an analysis of monthly and seasonal runoff volumes in two stages of the North Atlantic Oscillation are presented. The analysis embraced runoff at 146 profiles located on 96 Polish rivers during the years 1951–2000. The changes in the runoff conditions of Polish rivers in the two NAO stages and their spatial diversity were determined based on the differences between runoff observed in the years of exceptionally high (NAODJFM > 2,0) and low (NAODJFM < –2,0) values of the winter NAO index. The results of the research indicate that the influence of the North Atlantic Oscillation on the runoff of Polish rivers is diverse in terms of time and space. A classification of rivers was made in terms of the similarity of deviations of their seasonal runoff between the different NAODJFM stages. In the classification procedure use was made of Ward’s method of hierarchical grouping. In this way, five classes of the river profiles under analysis were obtained. Environmental conditions in the catchments and hydrological regime features clearly influence the regional differences in the impact of the North Atlantic Oscillation on the flow of rivers

Stability of high and low flow periods on European rivers

The aim of this paper is to examine regional differences in the flow regime of European rivers. The stability of a flow regime is defined as the regularity of high and low flow periods during a year (Corbus and Stanescu, 2004). The first, second, and third maximum and minimum values of the mean monthly flows during the year served as regime characteristics, i.e. descriptors of the regime phases. A series of monthly discharges recorded during the years 1951–1990 at 510 stations on 369 European rivers were analysed. The coefficient of stability used in the analysis enables an extension of classical hydrological regime analysis. The proposed approach allows not only to establish the term of high and low flow periods of the river, but it also shows the regularity (stability) of their occurrence.618319414Badania Fizjograficzn

Uncertainty of flow regime characteristics of rivers in Europe

The aim of the paper is to describe spatial differences in the uncertainty of features of the flow regimes of rivers in Europe on the basis of measures whose methodological assumptions derive from Shannon’s information entropy theory (1948). They included: the entropy of monthly flow volumes, the entropy of the flow distribution over time, and the entropy of maximum and minimum monthly flows. An analysis was made of monthly flow series for the years 1951–1990 from 510 gauging stations located on 369 rivers in Europe. It allowed a quantitative determination of the degree of uncertainty of the four regime characteristics, indirectly establishing the predictability, regularity and stability of their appearance and their spatial variability. In the procedure of identification of spatial differences among rivers concerning the uncertainty of their flow regime features, use was made of local indices of spatial dependence. On application of LISA (Local Indicators of Spatial Association) based on Moran’s local Ii statistic, a typology of rivers was obtained in terms of the kind and statistical significance of spatial associations involving the uncertainty of the flow regime variables in question

Odpływ rzek w Polsce w różnych fazach oscylacji północnoatlantyckiej

Deviations of climatic elements from average levels, like those caused by changes in the atmosphe- ric circulation, modify the conditions in which the river runoff forms. The river regime is controlled by both, precipitation and air temperature, whose magnitudes show a significant dependence on the intensity of zonal circulation. A simple indicator characterising the atmospheric circulation over the north Atlantic is the North Atlantic Oscillation Index (henceforth, NAO). The North Atlantic Oscillation is considered a very important climate-forming factor in Poland. The analysis embraced monthly, seasonal and annual runoff of Polish rivers taking into consideration Hurrell’s winter NAO index from the years 1951–2000. The analysed flow series came from 141 profiles loca- ted on 86 Polish rivers. The selected rivers are distributed evenly throughout Poland and represent a diversity of environmental conditions (Fig. 1). The aim of the present research was to examine the extent to which the North Atlantic Oscillation affects the runoff of Polish rivers: its seasonal structure and spatial variability. Differences were calculated between the monthly, seasonal and annual runoff observed in the years with exceptionally high (NAODJFM > 2) and low (NAODJFM < –2) values of the winter NAO index and their statistical significance was determined. Also calculated were monthly, seasonal and annual deviations of runoff in the years with high NAODJFM indices from that in the years with their low values (assuming the runoff in the years with low NAODJFM indices to be 100%). The research results have confirmed a strong effect of the North Atlantic Oscillation on the runoff volume of the Polish rivers. In the winter months – January, February and March, the most statistically significant positive relations can be observed on rivers in the north-east and north of the country. The river runoff in those regions in a positive NAO stage is then more than 200% higher than in a negative stage. In the spring months, in April hold for the runoff of rivers in north-eastern Poland and the middle parts of the Oder and Warta basins, and in May, rivers of almost the entire country with the exception of the east and south-east. In those areas stre- amflow in a negative NAO stage is more than 50% higher in a positive NAO stage. The obtained results show that the North Atlantic Oscillation has the greatest effect on streamflow in the winter-spring months, i.e. in the period when the most abundant water resources are being formed in Poland. Hence, in a positive NAO stage, one might expect a considerable buildup of the water resources in the winter months, mostly in the north-east, and their marked dwindling almost throughout the entire country in spring.A6112914

Zróżnicowanie reżimu odpływu rzek w północno-zachodniej Polsce

This paper seeks to identify features of the flow regime of rivers in north–western Poland in terms of runoff, structure, as well as temporal and spatial variability. The analysis was performed on the basis of hydrometric data of the Institute of Meteorology and Water Management from the years 1951–2010 coming from 46 gauging stations located on 33 rivers. The research embraced coastal rivers and lakeland tributaries of the Oder, Noteć and Vistula. In hydrological terms, this area is characterised by wide differences in flow conditions, as indicated by both, very great and very low water abundance. As a result, those rivers have different regime features, and on the basis of regularities in their flow variability they can be classified into 3 varieties of the nival hydrological regime. The rivers in this area display exceptional differences in total runoff, from the lowest values in the entire country (under 100 mm, the upper Noteć basin), to very high, the highest in the lowland part of Poland (over 300, and in the case of the Radunia even over 400 mm). They also show wide differences in their groundwater flow and its contribution to total runoff. For many coastal rivers this figure exceeds 80%, the highest in the country. Another of their characteristics is the lowest variability of discharges, especially annual ones. Also notable are the distinctly greater water abundance, higher groundwater flow and its share in total runoff, as well as lower variability of yearly discharges of streams in the eastern part of the coastal region than in its western area

Identyfikacja cech reżimu odpływu rzek w Polsce na różnych poziomach grupowania

The paper presents the characteristics of the river regime types in Poland which were obtained by applying the unsupervised approach to the regime based on the results of clustering rivers with respect to the values of the 12 monthly flow coefficients in the average annual cycle. In the paper were used daily flow values from the period 1971–2010 for 516 gauges located on 280 Polish rivers.On three clustering levels, 5, 9 and 12 varieties of river runoff regimes were identified and detailed. The paper also presents the spatial distribution of rivers that represent these variants

Typologia reżimu odpływu rzek w Polsce w podejściu nadzorowanym i nienadzorowanym

The paper presents a typology of the river regime in Poland obtained with the application of a supervised approach, i.e. a classic typology according to the assumptions of Dynowska with a regime typology obtained in an unsupervised approach by means of hierarchical grouping. In both cases, the explanatory variables were monthly flow coefficients – respectively: only from spring and summer months, with predefined threshold values, or 12-month flow coefficients. The paper applied daily flow values from the period 1971– 2010 for 516 gauges located on 280 Polish rivers. In both approaches, five types of regime were designated, including rivers characterised by a similar distribution and range of monthly runoff values in an average annual cycle. The designated groups, however, differ in abundance, which affects the image of spatial distribution of rivers representing the types of regime identified. The analysis shows that irrespective of the adopted method of designation, two types of regime, namely nival poorly developed and pluvio-nival are evidently characterised by different patterns of flow variability in an average annual cycle, and concern similar groups of rivers

Effect of North Atlantic Oscillation on the hydrological conditions of Lake Morskie Oko (Carphatian Mountains)

The paper presents the effect of North Atlantic Oscillation of macroscale atmospheric circulation (NAO) on the hydrological conditions of Lake Morskie Oko located at an altitude of 1392.8 m a.s.l. in the highest range of the Carpathians. The paper applied detailed hydrometric information from the years 1971-2010 concerning water level fluctuations, water temperature, terms of the commencement and end of ice phenomena and ice cover, as well as meteorological data concerning air temperature and atmospheric precipitation, and monthly and seasonal NAO indices. The performed analysis suggests that the majority of analysed hydrological characteristics of Lake Morskie Oko was not prone to variability of NAO intensity in its various phases. The situation results from the local conditions, particularly responsible for the course of processes and phenomena in Lake Morskie Oko, simultaneously obscuring the effect of macroscale factor

Seasonal structure of water stages on lakes in Northern Poland

The paper presents the characteristics of hydrological periods in an average annual cycle in Polish lakes. The type of periods and their sequence determine the regime of water stages in lakes. The article applies the unsupervised approach of analysis of the pattern of water level fluctuations, where the identification of the regime is performed through grouping analytical parameters. Hydrological periods were designated by means of grouping elementary time units of the hydrological year (pentads) based on the similarity of their parameters, namely the distributions of water level frequencies. The analysis covered daily water stages in 33 lakes in Poland from the period from 1984 to 2013. Five types of hydrological periods were designated. The studied lakes differ in the number, type, and sequence of hydrological periods in an average annual cycle. The most abundant group of 19 lakes includes lakes with a 4-period temporal structure of water stages with the course of water stages in a year characteristic of this geographical zone. No spatial patterns occurred in terms of location of lakes from particular groups. This suggests the dominant role of local factors determining the seasonality of water stages

Stability of the water levels regime on the lakes in Poland

The paper presents the results of a study into the stability of water-level regimes in Polish lakes. Stability is defined as a degree of regularity with which a certain phase of the hydrological regime occurs (high and low water levels). The hydrological regime is described with the use of the following 6 variables – first, second and third maximum; first, second and third minimum. Stability of the hydrological regime is determined by the stability coefficient (WS). The analysis relies on data concerning average monthly values of water levels for 34 lakes located in Polish lake regions. There are characteristic spatial differences in the stability of maximum and minimum water levels which are usually caused by environmental factors and human activity. It was observed that the most stable dates were those of the 1st maximum and the 1st minimum. In the case of the lakes in the Pomeranian, Wielkopolsko-Kujawskie and Mazurian lake districts, the occurrence date of the 1st maximum is highly stable and stable, while the date of the 1st minimum is the most stable in the lakes of the Drawsko, Wielkopolsko-Kujawskie and Mazurian lake districts.730531522Badania Fizjograficzn