The Europe-China Water Innovation Balance – Findings from the PIANO project ’ s mapping

Denmark has since the late 1980ties significantly reduced the N-leaching from agriculture, but must further decrease the N-load to coastal waters from agriculture areas to comply with the Water Framework Directive. Farmers are, however, already fertilizing below economical optimum and new regulatory strategies are required. A new spatially targeted regulation, taking spatial variation in natural N-reduction in groundwater into account, is under development. The objectives of this study were to analyse the potential benefits of a spatially targeted regulation based on detailed N-reduction maps and to analyse how uncertainty in the N-reduction maps affects the efficiency of such a regulation. Two ways of spatially targeting was examined: (i) Identification of target areas with low N-reduction where mitigation measures must be applied to reduce N-leaching to a defined level and (ii) redistribution of N-leaching on non-target areas according to the N-reduction maps, so that high leaching rates are relocated to areas with high N-reduction and vice versa. The study illustrates that there are potential benefits of implementing a spatially targeted regulation based on detailed groundwater N-reduction maps. The potential benefits are larger in Odense study catchment than in Norsminde catchment. The results show, that an increase in N-leaching can be allowed on non-target areas without increasing the N-load to surface water, if farmers at the same time implement a spatially targeted regulation. If spatially targeting is solely done by redistributing the present N-leaching a reduction of 8% in N-load can be obtained in Norsminde and 26% in Odense. Uncertainty on the N-reduction maps due to geological uncertainty is found to lower the efficiency of spatially targeted regulation since wrong target areas can be identified. The study shows that using the mean of an ensemble of N-reduction maps can lower this error. The uncertainty of the N-reduction maps decrease with increasing spatial resolution of the maps, but the study also shows that the spatial resolution greatly influences the efficiency of spatially targeted regulation. * alha@geus.dk, jcr@geus.dk, ika@geus.dk Depart. of Hydrology, Øster Voldgade 10, DK-1350 Copenhagen K ** jeo@agro.au.dk, christen.borgesen@agro.au.dk: Dept. of Agroecology, Blichers Allé 20, DK-8830 Tjele