A NSA was an area where nitrate concentrations in drinking water sources exceeded or was at risk of exceeding the limit of 50 mg/l set by the 1980 EC Drinking Water Directive. Voluntary agricultural measures were introduced by DEFRA as MAFF as a means of reducing the levels of nitrate with payments being made to farmers who complied. The scheme was started as a pilot in 1990 in ten areas, later implemented within 32 areas, with the aims of both reducing nitrate levels in areas where concentrations were high and providing information about the most effective agricultural management approaches for bringing about reductions. The Scheme was closed to further new entrants in 1998, although existing agreements continued for their full term. All the NSAs fell within the areas designated as Nitrate Vulnerable Zones (NVZs) in 1996 under the EC Nitrate Directive (91/676/EEC).Full metadata can be viewed on data.gov.uk.