The change of quantity and quality outflow of water in Ochożanka River basin

Abstract

The aim of this research work is to evaluate changes in the quantities of water and chemical parameters of outflow water from the forest catchment. Research was carried over a hydrological five-year period in the Ochożanka River basin (Western Polesie). The structure of the catchment area of 33.1 km2 is dominated by forestland constituting 81% of the area. During this period the precipitation amounted to 627 mm, which was 100 mm higher than the multi-year average. Precipitation of the summer half-year was almost three times higher than in the winter half-year. Data analysis shows that the average unit outflow from the catchment unit was 3.0 dm3·s−1·km−2. Outflow in the winter half-year was 52% higher than in the summer half-year. The waters of the river are used, they are usually characterized by good chemical status. In case 30% samples concentration of Kjeldahl nitrogen (>2 mg N·dm−3), total phosphorus (>0.4 mg P·dm−3) exceed the limit values for second class quality water. Indicators of oxygen conditions reach medium and high values. In spring, it happens that the limits are exceeded for second class water quality. These values are respectively COD > 20 mg O2·dm−3 and oxygen <5 mg O2·dm−3. An important issue related to the value parameters is the seasonal variability of their concentration in water outflow from the catchment. The maximum value chemical parameters are recorded in March, when the occurred largest outflows water.

Keywords

• forest catchment
• precipitation
• quality class
• water outflow