Delimitation of nutrient vulnerable zones - a comprehensive method to manage a persistent problem of agriculture

Agriculture, despite numerous efforts, still remains the key pressure on the aquatic environment causing an over excessive enrichment with nitrogen and phosphorus compounds. Therefore, an essential part of contemporary research and management endeavours to identify areas at risk. Presented here is a method of delimitation of such zones susceptible to nutrient pollution from agricultural activities. The starting point for its development, and subsequent construction, was the problem of Nitrate Vulnerable Zones of agricultural origin (NVZ), which still, as of yet, has not been resolved within the European Union. Surface component of NVZ (s-NVZ) areas have served as an example of a method application in a pilot catchment of the Warta River, which is one of the largest river catchments in Poland. The proposed method employs a mathematical algorithm using catchment modeling. The methods rely on a multi-stage delimitation procedure, which allows for precise delineation of only those areas within the catchment, which actually contribute to the analyzed problem (nutrient pollution and eutrophication). The method enables the user to benefit from a very extensive database, which can be modified in almost any way, depending on the current needs and local circumstances. It is also possible to expand this tools possibilities, connecting and coupling the used Macromodel with other modules or models. The proposed method can also be applied by countries that have recognized their whole territory as an NVZ area to designate areas particularly exposed to pollution (i.e. hot-spots). The proposed method applied for the pilot catchment resulted in an indication of 14 s-NVZs, occupying over 6800 km2 in total (13% of the catchment area). The indicated areas have been confirmed to have the largest share of agricultural pollution discharge into surface waters.