The aim of this study is to investigate the patterns and trends of drought occurrence in the northern part of Poland on the example of the Łeba river basin in the years 1956–2015. The study of meteorological drought was conducted on the basis of the Standardized Precipitation Index (SPI) on the scale of 1, 3, 6, 9, and 12 months. Annual precipitation totals did not show significant changes in the analyzed period, except for the station in Wejherowo, which is characterized by a significant increasing trend. The analysis of the long term of the variability average annual air temperature showed its statistically significant increase in the analyzed area at the rate of about 0.2 °C per decade. During the analyzed period, 14 to 84 meteorological droughts were identified, with durations ranging from 200 to 300 months. As the period of accumulating values of SPI, the number of droughts decreased, while their total duration increased. Most droughts were mild in nature, while extreme droughts accounted for between 5.2% and 10.7% of the duration. Drought intensification was shown only for SPI-1 in February and March in Wierzchucino station. On the other hand, a decreasing trend in SPI values was noted during longer periods of accumulation (SPI-6, 9, and 12).
The goal of this paper is to assess the impact of reservoirs on the water quality of watercourses in the urbanized catchment. To realize this goal Oruński Stream catchment was characterized with particular emphasis on retention reservoirs located within the catchment. Studies carried out were to show that these retention reservoirs change the water quality of the stream flowing through it and what the direction of these changes is.
There exist many classification systems of hydrographic entities such as lakes found along the coastlines of seas and oceans. Each system has its advantages and can be used with some success in the area of protection and management. This paper aims to evaluate whether the studied lakes are only coastal lakes or rather bodies of water of a completely different hydrological and hydrochemical nature. The attempt to create a new classification system of Polish coastal lakes is related to the incompleteness of lake information in existing classifications. Thus far, the most frequently used are classifications based solely on lake basin morphogenesis or hydrochemical properties. The classifications in this paper are based not only on the magnitude of lake water salinity or hydrochemical analysis but also on isolation from the Baltic Sea and other sources of water. The key element of the new classification system for coastal bodies of water is a departure from the existing system used to classify lakes in Poland and the introduction of ion-"tracking" methods designed to identify anion and cation distributions in each body of water of interest. As a result of the work, a new classification of lakes of the southern Baltic Sea coastal zone was created. Featured objects such as permanently brackish lakes, brackish lakes that may turn into freshwater lakes from time to time, freshwater lakes that may turn into brackish lakes from time to time, freshwater lakes that experience low levels of salinity due to specific incidents, and permanently freshwater lakes. The authors have adopted 200 mg Cl dm as a maximum value of lake water salinity. There are many conditions that determine the membership of a lake to a particular group, but the most important is the isolation lakes from the Baltic Sea. Changing a condition may change the classification of a lake.
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