Paweł Jokiel

The aim of the study is to identify the flow seasonality of the Vistula river in 14 water-gauge cross-sections located along the river course (from Skoczów to Tczew). For this purpose, the following characteristics were used: seasonality index (IS), period of seasonal concentration (PK) half-flow date (TPO), and concentration index (GMO).  Hydrometric data from the 1951–2016 period were shared by IMGW-PIB. The average time of seasonal concentrations and half-flow dates in the analysed cross-sections occurred in April or May. Along the Vistula river the mean PK and TPO regress towards winter (are earlier and earlier). The average seasonality index is comprised in the range 22–32%, while  the values of the concentration index fall into the range 10.0–14.5. The highest IS values characterize the upper part of the river down to the Goczałkowice water-gauge (here it reaches the maximum). Next the IS rapidly decreases, due to the summing of the flows from the Vistula river tributaries varying conditions of flow formation (from Carpathian Mountains and Uplands). A significant increase in the IS is visible below the mouths of the Dunajec and then the San rivers. A local maximum of the seasonality index occurs in the Zawichost cross-section. Next, the IS slowly decreases along the river down to the Vistula river mouth. One exception is the Włocławek water-gauge where a small increase of the IS can be noticed. It is due to the functioning of a dam and a big reservoir in the town. The changes of the concentration index along the Vistula river are similar to the seasonality index changes but the differences between the values of extremes are less visible. In the five analysed flood years, both the seasonality indexes and the concentration indexes were quite high in the upper part of the Vistula river and average in the central and lower parts of the river. The half-flow dates and the periods of seasonal concentration were stable along the whole river’s course but very diversified in particular years. The changes of the examined seasonality characteristics in dry years were very similar to analogical changes in normal years. Only in 1959 was the situation different when the IS was very low and the PK and TPO occured later and later down the river’s course.

The aim of the paper is to carry out a multi-faceted analysis of the changes and the multiannual variability of the seasonal structure of river runoff in Poland. The research study is focused on river catchments situated in various regions of Poland. The seasonality index (Markham 1970) is employed to provide an assessment of river discharge seasonality for a multi-year period using data obtained from 40 water gauges. The collected data include the daily discharge of the analyzed rivers in the period 1951–2010. Average seasonality indices of the discharge of the investigated rivers were computed. On the basis of average seasonality indices (8%–37%) and their variability levels in the studied multiannual period, it is possible to compute small differences in the magnitude and dynamics of the changes in the seasonal structure of river discharge and precipitation in the studied multiannual period (Kożuchowski, Wibig 1988) and the total outflow from river catchments in the central Poland (Bartnik, Jokiel 2001), respectively. At the same time, the seasonal structure of river runoff, it is conjectured, continually constitutes a stable part of the river regime in Poland over the years as well as across geographic space. However, statistically significant trends (α=0.05) for the obtained seasonality indices of river discharge in the multiannual period was identified only for seven rivers. On the one hand, the data indicate that the smallest seasonality of river discharge is a characteristic of lake district rivers in northern Poland. On the other hand, by contrast, the best seasonal structure of river discharge is typical of Carpathian rivers distinguished by apluvial–nival river regime as well as a nival–pluvial river regime, respectively. At the same time, the data suggest that lowland rivers characterized by a nival well-developedriver regime also feature a better seasonal structure of river discharge. Correlation coefficients (r) between the seasonality indices of river discharge of the studied  rivers and the seasonality indices of river discharge of other rivers account for the fact that the seasonal structure of river discharge has changed almost simultaneously with rivers, which are situated close to one another. At the same time, the seasonal structure of river discharge has changed similarly to that of rivers, which drain the same regions of Poland.

Abstract: Springs are objects of natural environment, which are studied by different scientific disciplines: geography, hydrology, hydrogeology, hydrochemistry, hydrobiology, ecology, environmental protection, landscape architecture, touring, archeology and ethnography. These objects, in both the past and the present, were of a great importance to  man, who, in different ways and very willingly, used the clean water flowing out and the surrounding environment. Springs, giving rise to streams, which feed into larger rivers, have great scientific, economic, natural, landscape, cultural and even therapeutic values. They have been protected from devastation and pollution for centuries, mainly due to the rational and often iconic perception of them. They were and still are objects of mystification resulting from the assignment of miraculous properties to their water and fantastic legends and historical events to places where they flow out. The question of the origin of water coming from springs has always been vividly discussed. It has contributed to both the development of natural sciences and to the creation of fantastic theories pointing to a specific “power” of these places and healing properties of discharging water. Interesting descriptions of springs that draw people’s attention have appeared in many travel experience stories, which brought them fame. Many springs have become places of worship, being famous for the descriptions of their healing abilities, related myths and fantastic phenomena, which additionally increased the desire to feel their “spirit”.

The area of Poland is already quite well recognized in the aspect of springs. The knowledge about Polish springs has definitely increased in recent decades, mainly as a result of research conducted at all academic centers of the country, as well as thanks to the work on consecutive charts of the Hydrographic Map of Poland. The oldest  information about springs in Poland can be found in historical records as well as in information and descriptions prepared for the needs of mining and balneology. Specialist publications and monographic views on springs and other groundwater outflows appeared in the middle of the 18th century. The springs of Małopolska were recognized at earliest. In the second half of the 20th century scientific works on the springs of the Tatras were published, followed by descriptions of the Carpathians, the Sudetes and the uplands: Kraków-Wieluń, Miechów, Lublin as well as the Nida Basin. Springs of the Łódź Region were also examined. At the end of the 20th and the beginning of the 21st century numerous issues, documenting the occurrence of springs and other outflows in the lowlands and lakelands of Poland, were also published. Despite the quite intensive research and passing years, the number of springs in Poland is still not known, not even estimated. Few outflows are monitored continuously. There are many reasons for this, including the disappearance and devastation of many objects because of anthropopressure and low interest in springs in hydrological and hydrogeological communities. It is probably due to the fact that springs operate at the boundary of the surface and the underground phase of the water cycle. In spite of this, dozens of springs in Poland have been studied in detail, in terms of hydrology, hydrochemistry, hydrobiology and water management.

The place of natural outflow of groundwater with the accompanying depression and water discharge stream creates the spring niche, and, in a wider perspective, the spring zone (the spring area). Such areas occur in various topographical, hydrographic and hydrogeological conditions. The way the water flows out as well as its dynamics and properties are also diversified. Springs waters, usually of a very good quality, have been used by humans for their needs for a long time. Their intakes form an important part of the water management infrastructure. At the same time, the sites of water outflow are important elements of natural and cultural landscapes, enriching them with new values and forms. Springs are often the objects of cultural and religious heritage and are tightly linked to the history of a given place or have a particular significance to the local community. They are sites willingly visited by tourists and recreationists. They provide the basis for the development of balneology and touring, as well as for the cult associated with the symbolism of water or religion.

Springs are important elements of geographical environment, they are also objects possessing unique scientific, landscape and water management characteristics. Due to their high susceptibility to anthropopressure, related to the frequent devastation of outflow sites and degradation of water resources, it is necessary to implement systematic and, nowadays, even urgent activities to preserve these places in their possibly natural state. Such protection should cover the place of outflow of underground water, the spring niche, as well as the groundwater basin. This task can be implemented by local communities, via administrative or ecological education, adequate to the course of actions and the significance of the local impact on the environment. In the case of particularly valuable springs, the establishment of protection zones, which would be similar to the preservation zones of public wells, should also be taken into account. However, to achieve this, it is necessary to recognize, calibrate and, above all, provide an inventory of all valuable springs in Poland.