Lake evolution in the Żnin region in the years 1912–1960 (central Poland)

The evolution of lakes, which, in the final stage, leads to their disappearance, is mainly based on the analysis of surface area change. However, there is one more, frequently overlooked process, which determines lake disappearance – namely the lake shallowing. The present paper presents the direction and rate of such evolution, taking both these processes into account. It is a comparative analysis of 9 lakes in the Żnin region – which has the greatest water deficit in the whole of Poland. Based on bathymetric plans from two periods (early 20th century and early 60’s of the 20th century), the author was able not only to evaluate the scale of surface area change but also to determine the value of lake basins volume change. Both these values were negative and amounted 9.1% and 14.9% respectively. Assuming that the said processes are invariable, the prospective period of lake functioning is about 500 years when taking into consideration surface area change only, and is 150 years shorter when allowing for aquatic resources change. The presented approach to lake disappearance analysis, which treats this phenomenon as a decline in aquatic resources rather than a simple decrease in surface area, is more reliable and therefore, scientific works in this field should take the results of lake shallowing into consideration

The effect of a water dam on Lake Powidzkie and its vicinity

The paper presents an attempt of assessment of the effect of damming of lakes on water resources based on the example of Lake Powidzkie (Central Poland) and its catchment. The analysed object is located in a region with the greatest water deficits in Poland. A co-occurrence of unfavourable natural and anthropogenic factors contributed to a considerable reduction of water resources retained in the discussed lake. Particularly low water levels were recorded in the 1990's and in the first decade of the 21st century. The situation was not improved by a water dam constructed on the outflow from the lake in the 1960's, among others due to neglect in its exploitation. Owing to the modernisation of the dam in 2010 and favourable hydrological situation in winter 2011, it was possible to retain excess water and substantially reduce its outflow. The restoration of the lost water resources, and hydrological benefits resulting from the fact were still observed several years later. Problems related to water deficits are becoming increasingly common in many regions of the world. A solution mitigating such a situation can be among others damming natural lakes. It is simpler, cheaper, and less invasive for the environment than the construction of new water reservoirs

Pedestrian safety: a new method to assess pedestrian kinematics

The progress in pedestrian safety enhancement is the result of multi-stage work, which is based mainly on the vehicle enhancement and appropriate traffic organization. However, the full separation of vehicle traffic and pedestrians seem to be impossible nowadays. The paper presents a new method for assessing the influence of vehicle structural components on pedestrian kinematics. An integral part of the method is the relationship, named as the k parameter, which can determinate the geometric property of the pedestrian body movement (kinematics) after a collision. The development of the new algorithm is the answer to the problem of assessing the risk posed by the impact of the vehicle with a high bumper/bonnet reference line (e.g. a Sport Utility Vehicle – SUV) on a pedestrian. The presented method can be a useful engineering tool to assess the safety of vehicles, both brand-new and used. The developed test system binds together a new defined kinematic criterion as well as the existing biomechanical criteria (the assessment of vehicles using pedestrian impactors). The presented method was verified on a compact vehicle and a SUV

Reconstruction of the primary bottom of a unique crater lake in the “Meteoryt Morasko Reserve” (Poland)

There are a total of several million lakes in the world, which includes only approximately 30 crater lakes. Due to this extreme global rarity, they are the subject of research in many scientific disciplines. In spite of the widespread interest in them, however, many issues still require detailed investigation. In the case of the Morasko crater lake (Poland), hydrological research has been weakly developed so far. The undertaken analysis, which employed a complex research procedure involving the use of georadar, geological corings and bathymetric measurements, aimed to determine the primary bottom of the lake, and further to determine the scale and rate of its evolution. The modern water level suggests that the lake basin is currently approximately 55% filled in with organic matter, and the rate of its sedimentation in the deepest place can be estimated at approximately 0.8 mm·y-1

Long-term water temperature fluctuations in coastal rivers (Southern Baltic) in Poland

The paper presents water temperature fluctuations in coastal rivers (Rega, Parsęta, Słupia, Łupawa, Łeba) located in the area of Southern Baltic Sea in Poland. Based on the available detailed data on daily values of the analysed characteristic in the years 1971-2015, tendencies of changes in the period were determined. In all of the five cases, the mean annual temperature showed an increasing tendency. The value of water warming in particular rivers was approximate, and ranged from 0.26°C∙dec-1 to 0.31°C∙dec-1. At the monthly scale, the highest increase was recorded in April, and amounted to 0.46°C∙dec-1 on the average. Water temperature fluctuations were particularly determined by climatic changes, and strongly correlated with air temperature. Local factors characteristic for coastal rivers, i.e. presence of infrastructure of small water power plants and predominance of groundwater alimentation, had secondary effect on changes in the thermal regime of the analysed 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

Tereny zalewowe w dorzeczu Prosny

Based on the data provided in hydrographic maps of Poland (1:50000), we can present the range and calculate the flood-hazard area in the Prosna river basin. It has been established that the total flood-hazard area amounts to 190.5 sq. km, which represents almost 4% of the river catchment. The largest areas of the type are located directly in the Prosna river valley (127.1 sq. km) and in the Pratwa river catchment (24.5 sq. km). On top of that, historical data on the water levels at the Bogusław station have been juxtaposed (1951-1983). An analysis of the average levels and the extreme annual levels has indicated that in the former case, no trend has been detected, while the extreme levels tend to have been growing. Therefore, a rising trend has been noted with reference to the emergency levels (250 cm) and alarm levels (300 cm). The year 1979 was exceptional in this respect, as the alarm level was recorded fourteen times, and the emergency level was recorded twenty eight times.56573Badania Fizjograficzn

Najnowsze sondowania wybranych jezior Pojezierza Wielkopolsko-Kujawskiego

The article presents the results of bathymeter measurements of formerly untested lakes of the Wielkopolskie and Kujawskie Lake districts with areas exceeding 50 ha. It has been established that the volume of water in the six lakes amounts to 22,980 [thou. cubic m.] while their total area amounts to 267.9 [ha]. The research results have enriched the available data on the bathymetric parameters of the region in question. At present, in the Wielkopolskie and Kujawskie Lake districts only one lake (with an area exceeding 50 ha) out of 193 has not been provided with detailed information about the hypsometry of the lake’s bottom. Bathymetric measurements conducted in various parts of Poland (both new and those updating the existing bathymetric plans) should be deemed valuable and necessary. These measurements provide a new source of information which serves, among other things, to evaluate the recent direction and rate of evolution of lake basins and the changes to the water resources stored in lake basins.55563Badania Fizjograficzn

The impact of global warming on lake surface water temperature in Poland - the application of empirical-statistical downscaling, 1971-2100

The paper presents historical (1971-2015) and scenario-based (2006-2100) changes in surface water temperatures in 10 lakes of Poland. The analysis of historical measurement (1971-2015) showed that mean annual lake surface water temperature (LSWT) was characterised by an increasing tendency by 0.37°C∙dec-1 on average, and was higher by 0.01°C∙dec-1 than air temperature in the analogical period. The highest increase in LSWT was recorded in spring months (April, May) and in summer (July). The future changes in LSWT was based on simulations of 33 AOGCMs available in the scope of CMIP5 project for RCPs: 2.6, 4.5, 6.0, and 8.5. The developed empirical-statistical downscaling models (ESD) use the air temperature field as predictors, with consideration of autocorrelation for two preceding months. ESD models are characterised by high quality of reconstruction of water temperatures in the historical period, with correlation from 0.82 (December, February) to 0.93 (July). The future CMIP5 scenarios for the period 2006-2100 assume an increase in air temperature at the end of the 21st century from +1.8°C (RCP 2.6) to +5.1°C (RCP 8.5) in reference to the period 1971-2005. According to the downscaling models, this corresponds to an increase in water temperature in the analysed lakes ranging from +1.4°C (RCP 2.6) to +4.2°C (RCP 8.5) in the years 2081-2100, respectively, with evident variability between the adopted emission paths beginning from the period 2041-2060. At a monthly scale, water temperature will increase the slowest in February (2081-2100: RCP 2.6 = +0.5°C, RCP 8.5 = +1.8°C). The highest increase in temperature will occur from May to August (RCP 8.5 = +6°C in June). Substantial effects of transformations of the thermal regime are already observed today, e,g. in the reduction of the ice season length. According to developed scenarios, a further considerable increase in water temperature will be the primary factor determining the transformation of lake ecosystems. The obtained results provide a theoretical basis for further research conducted in the scope of many disciplines, among others hydrology, hydrobiology, ecology, water management, energy production, etc. In the case of Poland, issues related to low water resources per capita are particularly important. Contemporary studies concerning changes in water resources showed that the natural factor playing the key role in their reduction is temperature increase and therefore it should constitute for the possibly fast development of multidisciplinary concepts of mitigation policy to potential impact of climate change