Search

A major part of Poland, classified geographically as Polish Lowland, is covered by a layer of loose or cohesive sediments whose thickness increases toward the north. Numerous authors emphasize the impact of the protrusion of the erosional base level on the course of processes shaping modern river valleys. It has been demonstrated, among other things, that the culmination of the sub-alluvial, cohesive bedrock determines the manner in which the channel zone and the adjacent floodplain are formed, which is associated with the hydrological system of the river. A number (12) of geological documenting holes have been drilled to the bottom of the valley. Also, geological profiles were recorded for 34 natural outcrops. The range of the individual outcrops was determined using a geomorphological analysis based on, among other things, the data from airborne laser scanning. The main objective of the research based on geomorphological criteria was to identify the differences in valley morphology and geological structure as well as the dynamics of currently occurring fluvial processes, along with geological features influencing their development, in particular in the middle course of a river. The research allowed the distinction of three geologically and geomorphologically characteristic sections. This allowed an answer to the question: why is the river in the lowland similar to a mountain stream.

The present paper discusses studies related to the preparation of a hydrogeological model of groundwater flow and nitrate transport in an area where a precision farming system is applied. Components of water balance were determined using the UnSat Suite Plus software (HELP model), while the average infiltration rate calculated for the study area equalled 20 per cent. The Visual MODFLOW software was used for the purpose of modelling in the saturated zone. Hydrogeological parameters of the model layers, inclusive of hydraulic conductivity, were defined on the basis of results of column tests that were carried out under laboratory conditions (column experiment). Related to the dose of mineral nitrogen used in precision fertilisation (80 kg N/ha), scenarios of the spread of nitrates in the soil-water environment were worked out. The absolute residual mean error calculated for nitrate concentrations obtained from laboratory and modelling studies equalled 0.188 mg/L, the standard error of the estimate equalling 0.116 mg/L. Results obtained were shown graphically in the form of hydroisohypse maps and nitrate isolines. Conclusions were drawn regarding the possibility of using numerical modelling techniques in predicting transport and fate of nitrates from fertilisers applied in precision agriculture systems.