This article attempts to assess the future occurrence of a drought using the Sieljaninova hydrothermal index (HTC). Air temperature and total precipitation were simulated for current conditions (2000) and forecast for eight locations of meteorological stations in Poland according to the HAD and GFDL scenarios for RCP 45 and 60 for 2040 and 2060.

Abstract. This paper presents the results of a study aimed at determining the possibility of water retention in the lakes located in the upper and middle reaches of the Noteć Zachodnia River in central-west Poland. The study was conducted on the basis of the analysis of available hydrological data and contemporary and archival topographic basemaps. The research was supplemented by a field study from the years 2011-2016, during which numerous surveys and hydrometric measurements were made. Their goal was to determine the natural range of water fluctuations in the lakes under consideration and to identify potential flows in the Noteć Zachodnia River.Observations and calculations allowed the determination of damming ordinates that are within the range of natural water fluctuations of the lakes. On the basis of this information and the previously prepared model of terrain, including the test area, the authors designated zones within the lakes at the required water level and calculated the useful and flood capacity of those water reservoirs. Subsequently, the possibilities of reducing the flood wave on the Noteć Zachodnia River were determined. Calculations were made for 2011, i.e. a year for which the highest winter spate for over 30 years has been documented. It has been shown that, by using only the flood capacities of surveyed lakes, it would be possible to reduce the flood wave on the Noteć Zachodnia River by 30% for the profile closing its catchment below Kamienieckie Lake.The results indicated the validity of damming the lakes located in the catchment of the Noteć Zachodnia River. Water retention in these lakes would restore the water resources in the area and allow reduction of the flood wave during heavy rains. This action would positively affect the ecosystems associated with the river system and would assist the flood protection system in central and west Poland.

The paper presents selected models for the estimation of diurnal total radiation on the basis of other meteorological variables (using simple data as temperature and rainfall) in the vegetation months in the territory of Poland. For that purpose 6 meteorological stations were selected, having standard meteorological data as well as total radiation data for the period of 2001 – 2010. The stations were chosen so that two of them were situated on the coast, two in the lowland part of the country, and two in the mountains. The models were evaluated with the use of the coefficient of determination R² and the relative error of estimation RMSE with division into 6 months and 6 meteorological stations. In each of the regions the best results were obtained for models 6 and 7 which are combinations of the remaining models and additionally the constructed variable ΔT, used in other non-linear models analysed in the other studies. The best fit for those models was obtained for the mountain stations (R² from 0.67 to 0.75, RMSE from 2.7 to 4.4). The poorest estimation was obtained for the coastal stations (R² from 0.41 to 0.67, RMSE from 2.6 to 5.1). The paper does not indicate the best month in terms of the fitting, due to the high variation of results for the stations and the models.

Water temperature is one of the basic physical parameters of rivers and lakes. Rising temperature can transform these ecosystems over a broad range of factors (water mixing, water quality, biological conditions, etc.). In the case of rivers, their thermal regimes also can be modified by local conditions (e.g., tree cover, adjoining water bodies, etc.). In this paper, we address the functioning of the river-lake system in northern Poland (Kocunia River-Lake Sławianowskie) in terms of the effect of the lake on temperature conditions in the river. Dependencies in daily water temperatures between stations located above and below the lake were assessed with linear regression. Based on daily morning water temperatures for the period 2012-2017, it was determined that water temperature in the river below the lake was higher than at the measurement site located above the lake by an average of 1.1°C. The greatest differences were recorded in summer-autumn months when average monthly downstream water temperatures were as much as 3.9°C higher than upstream water temperatures. This phenomenon is an example of a local factor (the lake) magnifying global factors, i.e. rising temperatures associated with climate change. The information in this paper can provide future reference for decision makers and state institutions with responsibility for measures aimed at reducing the effects of climate change.