The Zagreb aquifer is the main source of potable water for a quarter of the Croatian population. It is designated as part of the country`s strategic water reserves, protected by the Croatian State. Nitrates are defined as one of the five main groups of contaminants in the study area. Although there are numerous potential sources of nitrates, many studies showed a high correlation between agriculture and nitrates concentration in groundwater.. The main outcome of this project is the assessment of nitrogen pollution in drinking water and the dynamics of aquifer recharge, hence contributing to decreasing nitrate concentrations in drinking water.