Alternative strategies for reducing nitrogen loading

Two alternative strategies for reduction in nitrogen loading are analysed: (1) changes in agricultural production structure and (2) lake creation/rest oration. The former includes spatial redistribution of the agricultural pro duction, setting aside areas and changes in agricultural practice. The latt er includes five scenarios with different lake location and size. A 342 km( 2) agricultural watershed is used as study area. Two GIS-based models are a pplied: (1) a distributed riverine nitrogen loading model for analysis of a gricultural changes and (2) a linked-lumped model for lake creation analysi s. The analysis shows that each of the agricultural measures would result i n a 11-13% reduction. In combination they would amount to 30% reduction. Th e five lake scenarios were giving area specific reductions varying from 46 to 2375 kg N ha(-1) year(-1). The best lake creation strategy seems to be a high number of smaller lakes distributed in all parts of the watershed. Re sults indicate that comprehensive lake creation would result in a 20-30% re duction. The results emphasise the need for integrated watershed management .