Présentations Colloques

    Oral Presentation
    Session 7.03: Agricultural and sanitation contaminants and implications for water services and health
    Dottridge Jane
    40 years of rising nitrates and future concentrations in UK groundwater
    In response to the European directive on drinking water quality, the UK government commissioned a review of groundwater quality in the 1980s, which identified a growing problem of contamination by agricultural chemicals and industrial hydrocarbons. In the popular scientific press, the results were reported as ‘The hills are alive with nitrates’, but rising nitrate concentrations had already been highlighted by Foster and Crease in 1974. Despite this awareness, long term monitoring shows a rising trend in most of the UK’s major aquifers, with widespread exceedance of the drinking water standard of 50 mg l (as nitrate). This prevents compliance with Water Framework Directive ‘good status’ and requires treatment or blending for water supply. Modelling of nitrate fate and transport in the soil, unsaturated zone and saturated aquifers allows prediction of future concentrations, often continuing to rise. **Since 2010, most water companies have investigated catchment management, changing land use and farm management, as a potential environmentally and economically sustainable solution to improve groundwater quality. Working collaboratively with farmers and landowners, the pilot projects produced some significant reductions in nitrate concentrations, which then rose in two successive wet winters. **Although modelling indicates that catchment management can be effective more widely in the long term, many groundwater sources show little or no response to catchment management in the short-medium term, due to the aquifer properties and unsaturated zone thickness. As practical considerations and cost limit the extent of catchment management measures, identification of the most favourable areas is a priority. A GIS based approach was developed, combined with a sensitivity matrix to allow selection of priority areas. This was combined with modelling to estimate the rate and amount of changes in concentrations.**The approach, results and predicted future nitrate concentrations are illustrated for a range of hydrogeological settings, highlighting where catchment management could be most effective.**
    United Kingdom


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