The Aquisafe project aims at mitigation of diffuse pollution from agricultural sources to protect surface water resources. The first project phase (2007-2009) focused on the review of available information and preliminary tests regarding (i) most relevant contaminants, (ii) system-analytical tools to assess sources and pathways of diffuse agricultural pollution, (iii) the potential of mitigation zones, such as wetlands or riparian buffers, to reduce diffuse agricultural pollution of surface waters and (iv) experimental setups to simulate mitigation zones under controlled conditions.

The Aquisafe project assesses the effectiveness of natural mitigation zones in reducing diffuse pollution to surface waters. In one case study on a constructed wetland in agriculturally dominated Western France, nitrate concentrations from drainage inflows to a small river decreased up to tenfold on the way through an intermediary constructed wetland. However, only ~30 % of the total N-load is retained in the wetland, whereas ~70 % enters the river directly during high flow events as a result of low soil permeability. The study underlines the importance of flow paths and infiltration for nitrate removal in natural or constructed wetlands, which is often neglected in practice.