Improving the characterization of Quaternary deposits for groundwater vulnerability assessments using maps of recharge and attenuation potential

Assessing aquifer vulnerability is difficult for bedrock aquifers concealed by highly variable superficial deposits such as glacial till. Many current groundwater vulnerability maps, and the geological maps on which they are based, do not adequately account for regional and vertical variations in the characteristics of superficial deposits. A new method for characterizing recharge potential and contaminant retardation potential of superficial deposits is presented here, which captures primary geological and hydrogeological expert knowledge in a systematic manner. The method modifies existing superficial geology maps using Quaternary domains and their descriptions, bedrock lithology and thickness of superficial deposits, and applies additional information on superficial geology and bedrock lithology. Central to the method is a matrix that allows local geological and hydrogeological knowledge to be incorporated in a systematic and traceable manner. The scale-independent method has been piloted at 1:625 000 scale to produce maps of recharge and attenuation potential for Great Britain. Preliminary verification against several indicators (HOST data, the Scottish vulnerability screening tool, and nitrate data) has been encouraging. The method is being used by the Environment Agency as part of its vulnerability assessments for the characterization of groundwater bodies as required by the Water Framework Directive

Phosphorus in groundwater-an overlooked contributor to eutrophication?

This paper presents the first international assessment of phosphorus concentrations in groundwater, using data from the Republic of Ireland, Northern Ireland, Scotland, England and Wales. Phosphorus is considered to be the main limiting nutrient in most freshwater ecosystems. Controlling phosphorus inputs is thus considered the key to reducing eutrophication and managing ecological quality. Very little attention has been paid to evaluating transfers via groundwater due to the long-held belief that adsorption and metal complex formation retain the majority of potentially mobile phosphorus. In each country, ecologically-important phosphorus thresholds are exceeded in a significant number of groundwater samples. The relative contributions of potential sources for these elevated concentrations are currently unclear but there is evidence to suggest that they are at least partly anthropogenic. The results suggest that groundwater P concentrations are such that they may be a more important contributor to surface water phosphorus than previously thought. Copyright ¸ 2008 John Wiley & Sons, Ltd