Volume XV |

SWAT Model Application for Simulating Nutrients Emission from an Agricultural Catchment in Ukraine

Abstract: For the first time in Ukraine, a process-based watershed model SWAT was applied for the analysis of a surface water body contamination by nitrogen and phosphorus compounds. The model was applied in a small Holovesnya River Catchment (area 30.4 km2) located in the forest zone of Ukraine on the territory of the Desna water-balance station. The model run was in daily step for years 1985−1988, 2007, 2009, 2010, 2012. The calibration and validation within SWAT-CUP showed good results for streamflow (NS, R2 > 0.6, PBIAS < 4%), acceptable for nitrogen and phosphorus loads (NS > 0.6, RSR < 0.6, PBIAS < 43%).Streamflow and removal of nitrogen and phosphorus mineral compounds were to estimate the dependence of nutrient wash-off on the amount and practice of fertilizing were evaluated to provide recommendations for agricultural management. Increase of the amount of fertilizer results in the reduction of its efficiency. Divided application of fertilizer leads to the nitrate wash-off reduction by 66%.

Volume XV |

Field Experimental Studies of the Leaching of Humic Substances from the Peat Soils and Estimation of their Role in Dissolved Iron Transportation

Abstract: A field experiment on humic substances and dissolved iron transportation from the water catchment area was conducted in the spring time. The studies were carried out on a small runoff site (2x1m) filled with peat layer of 50 cm deep.During the snowmelt, exclusively a subsurface runoff was formed. The values of distribution characteristics of two main fractions of humic substances – humic and fulvic acids – between the solid phase of peat and water runoff were obtained. It has been shown that the process of complexing with fulvic acids significantly expands migration limits of iron in the dissolved phase. By means of thermodynamic modeling it has been found that the water pH value and the concentration of fulvic acids are the limiting factors for iron’s existence in a dissolved phase.A methodology has been proposed to predict emission of humic substances and iron into water runoff of the Pripyat River (Ukraine).