Nitrogen application rates had increased dramatically over past decades, so that a surplus in excess of that needed by crops or grassland was transported into freshwater systems. Application rates in the subregion are now widely declining in response to the legal framework summarised above, but the time taken for pollutants to move through the hydrological cycle means that in some areas concentrations in receiving waters may still be rising, even when the source itself is diminishing. Where trend data exists, this suggests that nitrate concentrations declined between 1992 and 2008 in 30% of rivers.