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Late Pleistocene and Holocene environmental evolution of the Wkra River Valley near Bielawy Gołuskie (central Poland) recorded in palaeo-oxbow lake deposits

Niska M., Jonczak J., Gadziszewska J.

Geological Quarterly

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2017

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Vol. 61, No. 2

305--318

EN

This study aimed to reconstruct environmental changes in the Wkra River Valley near Bielawy Gołuskie (central Poland) based on geochemical, palynological and subfossil Cladocera analysis of deposits filling a palaeo-oxbow lake. Two sediment boreholes collected from the palaeochannel bend (BG-1) and neck (BG-2) include full sequences of organic deposits lying on clastic deposits. The lower part of the BG-1 borehole contains gyttja that accumulated during the Younger Dryas and the Preboreal, which is covered by reed peat of Preboreal and Boreal age. On top of this is alder peat that accumulated during the Atlantic. The ages of the gyttja and peat were confirmed by both radiocarbon dating and palynological analysis. The peats are characterized by a significant content of organic matter, which is relatively stable over time. This indicates a low intensity of mechanical denudation in the catchment, which is supported by low concentrations of aluminum and potassium. Calcium values greatly exceed these elements, suggesting that the lake was mainly fed by groundwater. Variation in trophic conditions over time is indicated by a vertical variability in the content of nitrogen, as well as by the Cladocera population. The strong decomposition of peat in the top layer of the mire, and increased concentrations of phosphorus and heavy metals, testify to increasing human activity during the most recent time periods.

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The evaluation of hydrodynamic balance at the Wkra River estuary

Siwicki P., Urbański L., Hejduk L., Gładecki J.

Meteorology Hydrology and Water Management. Research and Operational Applications

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2016

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Vol. 4, iss. 2

29--34

EN

The river bed stability analysis at the Wkra estuary reach is presented in this paper. When a flood appears, channel and river bed erosion can reach a significant size. During such a situation, flow and water velocity exceed critical values for particular bed sediment grain sizes. This causes the breakage of bed armouring, and then bed mass motion begins. For the estimation of the sandy Wkra River bed the criteria of average velocity and bed armouring were applied with the use of ARMOUR software. The two Wkra River cross-sections at km 1+000 and km 3+200 distance were analysed. The calculation of the characteristics of bed sediment velocities was performed on the basis of, among other factors, probable river flow data, longitudinal slope, and grain size distribution of the bed. The results of the calculations were compared with average velocities in the analysed cross-sections. The results indicate the there is a threat to the stability of the Wkra River bed, especially during long-lasting high water stages. The prognosis of river bed stability loss performed by use of ARMOUR software shows that the bed armour breakage will take place in both considered cross-sections at relatively low water stages (about 40 cm), and mass motion of bed sediments in cross-section P-2 will occur at a flow of slightly lower than Q50% ,and in cross-section P-1 at flows greater then Q0,3%.

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Porównanie wartości współczynników dyspersji zanieczyszczeń pasywnych wyznaczonych z pomiarów na rzece Wkrze z obliczonymi zależnościami empirycznymi

Krukowski M.

Przegląd Naukowy Inżynieria i Kształtowanie Środowiska

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2002

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Vol. 11, No. 2

144--154

EN

The prediction of water quality in natural rivers requires the solution of the mass-transport equation. The accuracy of the numerical solution is highly dependent upon the accuracy of longitudinal dispersion coefficient. The values of dispersion coefficients calculated form easured concentrations in Wkra River have been compared with values calculated using existing empirical equations for the dispersion coefficient. Using statistical methods for analysis, has shown that the accuracy of calculated values is good for McQuivey and Keefer formulation.