AISUWRS work-package 4 : water quality of the Doncaster aquifer

This interim report comprises the fourth in the UK series of the project “Assessing and Improving the Sustainability of Urban Water Resources and Systems” (AISUWRS). Doncaster is one of the three European urban areas being studied in this European Community 5th Framework Programme-Shared Cost Research Technological Development and Demonstration project. It comprises part of Deliverable D10 for project Work Package 4. The report assesses groundwater quality in the Triassic Sherwood Sandstone aquifer supplying the case study town of Doncaster, England. Available data from stakeholders, principally Yorkshire Water, and from the project’s tripartite sampling programme have been collated and analysed. An understanding of the characteristics of groundwater from both the upper and middle/lower parts of the aquifer is emerging and has informed the conceptual model of evolution of water quality. In this part of the Nottinghamshire-South Yorkshire Sherwood Sandstone outcrop, recharge processes are complicated by the presence of variable Quaternary superficial deposits, which appear to control both the ease with which recharge can occur and the hydrochemical characteristics of the resultant groundwater. The data suggest that this complexity manifests itself in a degree of lateral variability of geochemical trends that is at least as great as that occurring with depth. The implication is that the degree to which the underlying saturated aquifer is affected by the contaminant load depends at least as much on local recharge conditions as the magnitude of the loading itself. At this interim stage of the field programme, the study has succeeded in initial hydrochemical characterisation of the principal constituents of the groundwater circulating in the mains water supply to the study focus area, the wastewater in its sewer system, the underlying and surrounding shallow aquifer and the deeper aquifer. Assessment of the urban recharge indicators of chloride, sulphate, boron and zinc has shown that these are likely to be only partially successful in Doncaster, for the following reasons: • the wastewater effluent load is relatively dilute • pollution from other human activities (agriculture, mining) is present within the same catchments, generating similar contaminant types and loading profiles • important relatively persistent contaminants found in urban wastewater such as sulphate and chloride also occur naturally and variably in the aquifer. Further work will be needed to unravel this complex system sufficiently to inform the urban water models that are being developed, linked and operated as the principal task of the AISUWRS project.