This paper presents the characteristics of the chemistry of surface and ground water in the bottom of the river valley reclaimed Ochoza. Drained grassland accounts for 20% of the total catchment area and are located on organic soils in the valley Tyśmienica classified to the Natura 2000 sites. Analysis of physico-chemical properties of water are to assess the effects of anthropogenic transformation and identify factors that influence water quality in the study area. Water samples were collected in the years 2011–2012 in several points. The walls were characterized by surface water stagnant in the trenches, in July, blueberry plantation. Characterized by the highest quality of surface water runoff river with the test object. Occurring here throughout the growing season water flow reed growing on the bed and temporary impoundment of water contribute to the self-cleaning effect of water. Conducted at different times of the growing season (winter, spring, summer, autumn) of water chemistry analysis allows to assess the impact of vegetation on the process of self-purification of water. Based on the survey it was found that the river is reduced by 26% BOD 5, COD by 37%, 12% phosphate and potassium by 13%. Concurrently, an increase in the content of nitrogen compounds – ammonia at 27% and 15% nitrate. The increase in the content of nitrogen compounds is particularly evident in the bottom of the object, which is probably associated with the deep trench causing excessive drying of the soil. The highest values of pollutants were recorded mostly in the spring probably due to the outflow of water from the drans.