Catchment planning and the nitrate issue: a U K perspective

The imposition of strict water quality standards by the EC had prompted renewed interest in catchment planning in the UK. This article examines nitrogen cycling in rural catchments, placing particular emphasis on the delivery of nitrate to the stream system. Nitrate levels in UK freshwaters are reviewed. Over the last two decades increases in nitrate concentration have been noted for many rivers, both large and small; in many cases, this increase can be related to the intensification of agricultural practices. Evidence is presented which shows that nitrate concentrations in many lowland rivers are close to, and in some cases exceed, EC limits for nitrate in drinking water. In southeast England, only the chalk aquifer provides low-nitrate water at present, though evidence suggests that the unsaturated zone of the aquifer is already heavily polluted by nitrate. The possibility of controlling nitrate loss by managing land use is discussed, including the implications of recent EC legislation; the UK's pilot Nitrate Sensitive Area scheme is briefly reviewed. The paper ends with a description of the authors' own research on riparian buffer zones.