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1

Impact of climate fluctuations on the spring runoff regime with regard to rivers in Lithuania

100%

Bagdziunaite-Litvinaitiene L. , Litvinaitis A.

Journal of Water and Land Development

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2015

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nr 25

2

Impact of climate fluctuations on the spring runoff regime with regard to rivers in Lithuania

100%

Bagdžiūnaitė-Litvinaitienė L. , Litvinaitis A.

Journal of Water and Land Development

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2015

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tom no. 25

23--30

EN

The article describes the impact of fluctuations in climatic factors on hydrological processes. The analysis of climate and hydrology covers two periods, the first up to 1996 and the second from 1981 to 2012. Study object includes 22 river basins situated on the eastern coast of the Baltic Sea: 1000 km2, up to 10 000 km2 and bigger. The study involved Mann–Kendall, Spearman's and linear regression tests. Causal relationships, as criteria that may fundamentally change the runoff regime set up by climatic factors, were established by evaluating the size of the river basin and assessing the spread of sediments, lakes, swamps and forests in the river basin. The analysis of data from the last thirty years disclosed that, with reference to the previously obtained information, floods in lakes became substantially reduced. Nevertheless, within the winter period of recent years, temperatures prevented lakes from acting as water reservoirs. The paper examined and defined the impact of sediments on variations in the runoff regime. For the period of the last thirty years, cut-off dates, i.e. flood start, crest and end, have advanced.

PL

Przedmiotem artykułu jest wpływ czynników klimatycznych na zmianę procesów hydrologicznych. Dokonano analizy klimatycznej i hydrologicznej dwóch okresów: do roku 1996 i od roku 1981 do 2012. Obiektem badań były zlewnie 22 rzek we wschodniej części wybrzeża Morza Bałtyckiego: do 1000 km2, do 10 000 km2 i większe. W badaniach stosowano testy statystyczne Manna–Kendalla, Spearmana i regresji liniowej przeznaczone do ustalenia związku przyczynowego w ocenie wielkości zlewni rzeki, osadów, jezior, bagien, zalesienia w zlewni rzeki jako kryteria, które w zasadniczy sposób mogą zmienić reżim odpływu ukształtowany przez czynniki klimatyczne. Analiza danych pochodzących z ostatnich trzydziestu lat wykazała, że według wcześniejszych danych jeziora w większym stopniu ograniczały występowanie powodzi, jednak w ostatnich latach temperatura w sezonie zimowym nie pozwala jeziorom pełnić funkcji akumulatorów wodnych. Zanalizowano i określono wpływ osadów na zmiany reżimu przepływu. Stwierdzono, że w ciągu ostatnich trzydziestu lat graniczne daty powodzi – początek, szczyt i koniec – notowane są wcześniej.

3

Assessing the impact of the turbulence of river flow on variations in the concentrations of nutrients

100%

Bagdziunaite-Litvinaitiene L. , Litvinaitis A.

Environment Protection Engineering

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2017

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tom Vol. 43, nr 3

81--91

EN

The fourth-order stream of the Baltic Sea has been analysed, which is a tributary which remained in the riverbed as a result of natural river stretches not corresponding to the status of good water quality. The authors examined separate river stretches representing maximum changes in the hydraulic gradient and investigated the dependence of variations in the concentrations of biogenic nutrients on river flow velocity, i.e., turbulence, defining it by the Reynolds criterion. The calculation of the coefficient of self-purification provides that the river flowing downstream is 100% self-purified and removes all nitrates and 61% of phosphates. The content of dissolved oxygen at the confluence of the river in spring was by 5.5% larger than that at the headwaters, whereas in the summer season, the difference in the content of dissolved oxygen in river water between the headwaters and confluence increased and made 25%. The conducted research has disclosed that the dynamics of river flow affects water quality, and therefore, for selecting monitoring places, land use structure or economic entities situated around the sampling point as well as the nature of the river flow itself must be considered.

4

Assessment and research of river restoration processes in regulated streams of southeastern Lithuania

61%

Survile O. , Saulys V. , Bagdziunaite-Litvinaitiene L. , Stankeviciene R. , Litvinaitis A. , Stankevicius M.

Polish Journal of Environmental Studies

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2016

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tom 25

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nr 3

EN

The article deals with the auto-naturalization problems of regulated streams in Lithuania. Research on such streams overgrown with woody vegetation was conducted in the Neris River basin in the Baltic Highlands. We chose to investigate the most urbanized rough terrain area of southeastern Lithuania. The regulated streams found in this area include stretches with a relatively high reserve of hydraulic conductivity. Therefore, with reference to the Water Framework Directive for improving the ecological situation, we assessed the possibilities of promoting the naturalization process. The average density of woody vegetation on the investigated slopes of regulated streams is T = 1.26±0.20 items m-2. The slopes with northeastern exposure point to the average density of woody vegetation counting TNE = 0.91 items m-2, which is 2.42 times more than that observed on the slopes with eastern exposure and 2.30 times more than those with southern exposure (TS = 0.39 items m-2). Under the presence of the recent density of woody vegetation, hydraulic measurements established Manning’s roughness coefficient that varied from 0.030 to 0.094. The conducted simulation indicates that the studied stretches of regulated streams lose a margin of hydraulic conductivity when Manning’s roughness coefficient reaches a threshold of 0.060-0.080. Planning the naturalization of regulated streams is first offered in the stretches of higher slopes (S0>0.003), where the maintenance of the adequate roughness of the bed may assist in designing the overgrowth of both slopes with woody vegetation.

5

Evaluating the impact of neogene sediments on river runoff formation

61%

Litvinaitis A. , Bagdziunaite-Litvinaitiene L. , Saulys V. , Barvidiene O. , Stankeviciene R. , Cesnulevicius A.

Polish Journal of Environmental Studies

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2015

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tom 24

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nr 4

EN

Due to the recently increasing frequency of extreme changes in river runoff regime, scientific literature has dealt with the characteristics of runoff formation. Studies have been carried out on analyzing climate change and a lot of attention has fallen on land-use structures. Migration of precipitation through the river basin is influenced by the lithological composition of sediments. Its structure is determined by analyzing geological and geomorphological maps and by drilling boreholes in the selected area. With the help of boreholes the level of groundwater and lithological composition of sediments can be assessed. An installed system of lysimeters and piezometers in the borehole allows us to monitor the change of groundwater level and the amount of water moving through the unsaturated zone of sediments over time. The set of lysimeter boreholes allows us to capture and map the spacial change of these parameters. Following thorough analysis of the lithological structure of river basins in separate costal zones, this article aims at evaluating river runoff formation characteristics. The basin lithological factor was calculated based on large-scale maps using ArcGis software. In order to carry out more thorough analysis of the influence of lithology in given territories, sections of 0-50 m, 50-200 m, 200-500 m, 500-800 m, 800-1000 m, and >1000 m were established, calculating the distance in meters from the riverbank. Eight river basins of typical lithological structure (sandy, loamy, argillaceous) were selected and examined. The period of the year 1960-2013 was analyzed as this period and the relationship between the runoff and precipitation with correlation of 0.72-0.83 was established, as well as that with the lithological structure, established following the derivation of a hydromodule.