Nitrate Leaching to Groundwater

Groundwater provides over 30% of developed supplies of potable water in Britain. The outcrops of the important aquifers form extensive tracts of agricultural land. Groundwater resources largely originate as rainfall that infiltrates this land. During the 1970s, growing concern about rising, or elevated, groundwater nitrate concentrations, in relation to current drinking water standards, stimulated a major national research effort on the extent of diffuse pollution resulting from agricultural land-use practices. The results presented derive from intensive and continuing studies of a number of small groundwater catchments in eastern England. It is in this predominantly arable region that the groundwater nitrate problem is most widespread and severe. The distribution of nitrate in the unsaturated and saturated zones of the aquifers concerned is summarized. These data have important implications for the water-supply industry, but their interpretation is discussed primarily in relation to what can be deduced about both the recent and long-term histories of leaching from the more permeable agricultural soils.