The use of conventionally and alternatively located buffer zones for the removal of nitrate from diffuse agricultural run-off

Abstract

Interest in the use of buffer zones for the protection of surface water bodies from diffuse agricultural pollution is increasing in the UK. Current protocol for buffer zone location recommends they are established adjacent to the water body, typically in the riparian zones of rivers and streams. In many situations this may be the most efficient location to deliver benefits such as habitat provision and river bank stability, though this may not necessarily be the case for effective reduction of diffuse pollution. In the UK many of these riparian locations are by-passed by drains and ditches, rendering them ineffective as buffer zones for reducing pollutant concentrations in ground water and surface water. Alternative wetland buffer zone locations have often been found to be more effective for nitrate removal. These include areas of both footslope seepage and overland flow often associated with small ditch systems, which traditionally would not be considered as buffer zones. Examples are presented of two alternative wetland buffer zones in south-west England, one situated in an area of footslope discharge, and the other on an overland flow zone associated with a ditch system. The potential efficiency of both buffer zones is examined with regard to nitrate removal.