Hydrological models can be useful tools simulating climate and land use changes and their impact on nutrients outflows from a catchment area. One of them is the HYPE (HYdrological Predictions for the Environment) water quality model applicable to different spatial scales. Groundwater recharge via infiltrating precipitation is a significant water budget component. The rate of groundwater recharge in the HYPE model is estimated from the water balance in soils. The Kocinka river catchment is one of the test areas in the BONUS-Soils2Sea project where HYPE model modelling was carried out. A hydrograph, among others, is one of the modelling results and, based on it, the recharge rate of groundwater was determined. This value was compared with groundwater recharge rates estimated by the infiltration method used for the Groundwater Vulnerability Map of Poland.

The paper presents basic assumptions and results of a non-stationary MODFLOW model of nitrate transport in the Kocinka catchment. A method of reconstructing temporally and spatially variable input function of pollution for two main contamination spots: agriculture and urbanized areas, is presented. The NLES4 software was used to assess loads of nitrogen leaching from agricultural areas. Presented are also: representation of denitrification process in the model, the results of its calibration and the modelled nitrate breakthrough curves.