Anna Uciechowska-Grakowicz

Reintroduction of European bison into the natural environment is one of the most important conservation measures applied for this species. After creating a free herd of European bison, spatial monitoring is crucial. It allows for observation of the population, as well as the detection of potential threats and needs for intervention. In 2016, a new free herd of European bison was introduced to the Żednia District in Knyszyńska Forest. After a few months spent in the acclimation enclosure, the animals were released. The course of their acclimatisation was observed with GPS collars during the next 7 years. Thanks to telemetry monitoring, we could determine the moment when the herd stabilised its home range within available habitats. Monitoring performed for 7 years after the release of the herd confirmed the previously established home range. The fact that the animals remain close to the release site and that there is no damage to the winter crops confirms that the reintroduction site was well chosen.

In this contribution, interpolation methods were assessed to build the bathymetry of 200 km of the Odra River in South Poland. The River Bed Mapping (RBM) was carried out surveying the depth of several reaches of the canalized part of the river using an Global Navigation Satellite System (GNSS) with an echo sounder as well as two navigation schemes. The values from the interpolation were compared with the data from a classical cross-sectional survey as part of the ISOK (Polish acronym for Information System of Country Protection Against Extraordinary Hazards) project. Two statistical errors between the interpolation values and the ISOK information were estimated, namely, the Mean Absolute Error (MAE) and the Root Mean Square Error (RMSE). Thanks to the presented analysis, it was possible to compare and analyze which interpolation method fits the best for the batymetric surveying of a shallow river. For this specific case study, the TIN (Triangular Irregular Network) and the NN (Natural Neighbor) methods generates the most accurate RBM.

This article presents the results of numerical simulations of seepage through the body of the dam and the reservoir bed. The purpose of this study was to analyse the seepage stability during a flood as well as the impact on seepage stability of the diaphragm wall and gravel columns, on which the dam body is founded in selected segments. Simulations were conducted for three different locations, and the following 3D models of the dum were prepared: – a model containing the front and right-bank part of the dam, for which no diaphragm wall, gravel columns and drainage ditch were provided for – a model of a segment of the right-bank dam including a diaphragm wall, drainage ditch and gravel columns under the dam (two variants with differing diaphragm wall lengths) – a model of the water dam segment accounting for gravel columns and a drainage ditch, but without a diaphragm wall. In the case of founding on gravel columns, the base was modelled as an anisotropic medium in terms of seepage properties, macroscopically equivalent to the actual soil medium. The numerical model utilises the finite element method. The geometry of the dam and geological substrate was defined in the GIS tools in the form of a 3D model of the terrain and geology of the substrate.

In the case of a two-phase medium – such as the soil, which consists of an elastic skeleton and is filled with pore fluids – stress and strain within the medium are dependent on both phases. Similarly, in the case of heat transfer, heat is conducted through the two phases at different rates, with an additional heat transfer between the phases. In the classical approach to modelling a porous medium, it is assumed that the fluid filling the pore space is water, which is incompressible. In the case of gas, the volume of which is strongly dependent on temperature and pressure, one should take this behavior into account in the constitutive relations for the medium. This work defines the physical relations of a two-phase medium and provides heat transfer equations, constructed for a porous, elastic skeleton with fluid-filled pores, which may be: liquid, gas, or mixture of liquid and a gas in non-isothermal conditions. The paper will present constitutive relations derived from the laws of irreversible thermodynamics, assuming that pores are filled with either a liquid or a gas. These relations, in the opinion of the authors, may be used as the basis for the construction of a model of the medium filled partly with a liquid and partly with a gas. It includes the possibility of independent heat transfer through any given two-phase medium phase, with the transfer of heat between the phases.

In this paper, the results of numerical analysis of the thermal consolidation of a two phase medium, under the assumption of independent heat transfer in fluid and the solid phase of the medium, are presented. Three cases of pore fluid were considered: liquid, represented by water, and gas, represented by air and carbon dioxide. The mathematical model was derived from irreversible thermodynamics, with the assumption of a constant heat transfer between the phases. In the case of the accepted geometry of the classical dimensions of the soil sample and boundary conditions, the process leads to equalization of temperatures of the skeleton on the pore fluid. Heat transfer is associated with the fluid flow in the pores of the medium. In the case of gas as the pore fluid, a non-linear mathematical model of gas filtration through the pores of the medium was accepted. For the computing process, relationships between viscosity or density and temperature proposed by other authors were taken into account. Despite accepting mechanical constants of the solid phase that do not depend on temperature, the obtained model is nonlinear and develops the classical Biot–Darcy model.