|
To implement the European Water Framework Directive (WFD) into German law, measures have
to be taken to reduce the unacceptably high nutrient input into rivers. To identify the most
effective measures, the sources and pathways of nutrient emissions into rivers have to be
quantified. Therefore, the MONERIS model is applied, which quantifies nutrients emissions into
river basins, via various point and diffuse pathways, as well as nutrient load in rivers. Most
nitrogen emissions come from groundwater flow (43%), tile drainages (30%), and point sources
(12%), whereas most phosphorus emissions come from groundwater flow (31%), point sources
(23%), erosion (13%) and overland flow (12%). Because of their great distance from the river basin
outlet, the southern sub-basins Werra and Fulda-Diemel have an 8% reduction in their nitrogen
loads and a 15% and 16% reduction in their phosphorus loads, respectively. This reduction is due
to retention in the main part of the river Weser. For the choice of the most effective measures,
the different retention in the river is relevant.
|
