Simulating 50 years of land management and groundwater flow

Aquatic ecosystems can be strongly distorted by high nitrate inputs from intensive agriculture. Starting in the early 90-ies, the Flemish government has imposed increasingly stringent fertilization regulations on farmers in order to comply with the EU Nitrates Directive, but despite this, nitrate concentrations remain high in many surface waters. This may be the result of a substantial inflow of old nitrate-rich groundwater. In this study, we aim to define the expected delay for the achievement of water quality goals in those waters by simulating historical nitrate leaching towards groundwater and by determining origin, age distribution and pathways of groundwater inflow.

Elevated nitrate concentrations in both ground and surface water are a common problem in regions with intensive agriculture such as Flanders. Fertilizer restrictions have in many catchments been awarded with reduced nitrate concentrations, but not everywhere. In catchments with substantial nitrate-rich baseflow, the response may be delayed due to long travel times of historically contaminated ground water travelling through oxidized parts of the aquifer systems.