Investigation of the potential of denitrification in shallow groundwater to mitigate nitrate concentrations in Flemish surface water bodies.

Despite extensive efforts, nitrate concentrations in the surface water continue to rise in some regions in Flanders, suggesting additional knowledge is necessary to reach future targets. In this context, fundamental insight in the relation between groundwater and surface water is becoming increasingly important. One relatively unknown and promising factor is denitrification in the groundwater. In this project, the potential of denitrification in shallow groundwater as a measure to reduce nitrate concentrations in surface water will be investigated.

Measurements will be collected using the push-pull method. A known amount of 15N-labelled nitrate is added to the groundwater and denitrification can be calculated from the share of 15N-labelled denitrification products. To achieve the best results possible, the method will be optimized for application in Flanders in a carefully selected test region. Since push-pull measurements are too labour-intensive and time-consuming to be collected all over Flanders, another approach is followed to obtain useful information on a Flemish scale. For a wide variety of relevant parameters, data are available for every region in Flanders. Push-pull denitrification measurements will be collected on 20 sites in Flanders and these measurements will be analysed for possible correlations with data already available. These results will then be validated for the rest of Flanders. A parallel experiment will be set up to investigate whether cover crops can lead to an increase in denitrification.