Hydrogeochemistry of aquifer storage and recovery in the Lower Greensand (London, UK) for seasonal and drought public supply

Investigations are in progress to determine the potential for ASR, in the Cretaceous Lower Greensand aquifer at Horton Kirby, to meet demand during droughts of up to 2 years, whilst also meeting normal seasonal demands. The sands and sandstones are glauconitic and ferruginous so an understanding of the hydro geochemistry is needed to predict the responses to injection of aerobic water from the overlying Chalk aquifer. Pumped and pore water from the aquifers have been characterised, microcosm experiments undertaken and the results used to constrain geochemical modelling. The transmissivity of the 23 m thick aquifer is calculated to be 45 m2/d and it contains Ca-HCO3 type groundwater with a pH of 7.6 and a SEC of 329 μS/cm. Concentrations of Fe(total) and Mn exceed the prescribed concentration value (PCV). The water to be injected is also a Ca-HCO3 type with a pH of 7.4 and a SEC of 537 μS/cm, is aerobic and contains elevated concentrations of nitrate (22 mg/l), but not in excess of limits. Likely impacts of ASR are reactions with Fe-minerals (including small quantities of pyrite) resulting in an increase in dissolved iron and sulphate, and removal of injected nitrate through reduction

Catalogue of geothermal data for the land area of the United Kingdom : first revision: August 1981

A comprehensive catalogue of underground temperature, heat flow and geochemical data was first published by the Department of Energy in 1978 (Burley and Edmunds) It was compiled under the terms of contracts drawn between the Commission of the European Communities, the Department of Energy and the Natural Environment Research Council in association with its component body the Institute of Geological Sciences. This First Revision of the earlier catalogue was prepared under an extension of the same contractual arrangements. It incorporates new data acquired since the first catalogue was completed in June 1977, and it also includes the data published in the first catalogue. Revisions of the original maps, however, are not included and readers will themselves need to add the locations of new data to those maps. Reference should be made to the original publication for an account of how the tables are compiled but an explanation of the various columns of data is given at the beginning of each table. A further revision is planned in 1984 when it is intended to publish a fully revised version of the catalogue

Investigation of the geothermal potential of the UK : catalogue of geothermal data for the land area of the United Kingdom

A comprehensive catalogue of undergound temperature, heat flow and geochemical data was first prepared in 1977 by the Institute of Geological Sciences (now renamed the British Geological Survey) and published by the Department of Energy in 1978. It was compiled under terms of contracts between the Commission of the European Communities (CEC), the Department of Energy (DEn), and the Natural Environment Research Council (NERC) in aSSOCiation w1th its component body the British Geological Survey (BGS). A first revision of the earlier catalogue was published by IGS in 1982 incorporating new data acquired between June 1977 and August 1981 and including the data published in the first catalogue. 'lhat revision comprised listings of the underground temperature, heat flow ana geochemical" data but not the maps or detailed notes incorporated in the original catalogue. This second revision of the catalogue incorporates new data acquired between August 1981 and April 1984 and includes data published in the previous catalogues. This catalogue has also been prepared under contracts between the DEn, the CEC and the NERC in association with the BGS. The text of this catalogue has been written by A J Burley, W M Edmunds and I N Gale. Canpilation and editing of the data on computer files from which this catalogue has been produced has largely been carried out by S J Whitting using programs written by M T Houghton (Tables I and II) and R Andrews and D G Kinniburgh {Table III>. 'nle work has been supervised by R A Downing under the general direction of D A Gray

Geochemical modelling of fluoride concentration changes during Aquifer Storage and Recovery (ASR) in the Chalk aquifer in Wessex, England

During ASR-cycle testing at a site in the confined Chalk near Lytchett Minster in Dorset, the high concentration of fluoride in the recovered water posed severe limitations on the success of the scheme. Based on physical modelling, the dual porosity character of the Chalk combined with high fluoride concentrations in the native water were identified as the key factors controlling the measured concentrations. However, mixing of water between the matrix pores and fractures was not sufficient to explain the fluoride concentration and it was concluded that there was an additional release of fluoride from aquifer interaction. This led to an additional increase in the fluoride concentration in the recovered water. In order to investigate this hypothesis, a geochemical model incorporating reactions between the injected water, the native groundwater and the aquifer minerals was developed. The geochemical model PHREEQC-2 was set up so that it was capable of modelling ASR-cycles (including radial flow and diffusive mixing as a consequence of dual porosity). The physical aspects of the model were calibrated using a 3-D dual porosity transport model (SWIFT). Different geochemical processes (e.g. limited mineral availability, reaction kinetics) causing fluoride concentrations above those expected from dual porosity mixing were investigated. Comparing the modelled results with the observations from the test site suggested that slow dissolution of fluoride minerals (fluorite) was likely to be responsible for the additional increase in fluoride concentration in the recovered water

Augmenting groundwater resources by artificial recharge (AGRAR): progress of activities May-November 2003

Progress of the DFID-funded KAR project entitled “Augmenting Groundwater Resources by Artificial Recharge” – AGRAR (R8169), was reviewed in early November 2003 at the three research sites and during a meeting of all partners in Ahmedabad, Gujarat. Draft inception reports for the three research sites and review reports for the two ancillary studies were presented and discussed by all partners. It was agreed that final draft versions of these reports would be prepared by mid-December 2003 for publication on the project web page in January 2004. The delay in initiating the instrumentation and surveys at the three research sites has resulted in significant loss of data during the 2003 monsoon season. However, the conceptual understanding of the sites has improved and aspects that need to be monitored have been more closely identified. For example, the understanding gained from monitoring water levels in wells around recharge structures has helped in the siting of observation boreholes that are currently being drilled in preparation for monitoring through the forthcoming monsoon season. The work undertaken, at some of the research sites, by the related ComMan1 project has provided a valuable basis on which to build in order to achieve the distinct objectives of AGRAR. This has been especially the case with the rural livelihoods surveys which, in ComMan, have addressed the issue of demand management in the context of community approaches to managing groundwater resources, and have set out to examine whether hydrogeological, institutional and socio-economic conditions exist to enable such user-based schemes to be set-up and sustained. The AGRAR project will complement these activities by focusing on the potential and effectiveness of augmenting groundwater resources, while ComMan will concentrate on the challenges associated with controlling the demand for groundwater. Surveys and methodologies have therefore been designed to build on the findings of ComMan in order to specifically address the impacts of artificial recharge structures on the livelihoods of the communities. The AGRAR project was commissioned by DFID to address the specific issue of the effectiveness of artificial recharge structures, from both the technical and socio-economic perspectives. This is being done in the context of other projects being undertaken by a range of organisations; government, NGOs and researchers. Contact with these organisations has been maintained in order to learn from their experience and hence avoid duplication. A brief review of the relationship of the activities of AGRAR in relation to other projects is given

Investigation of the geothermal potential of the UK Heat flow and regional groundwater flow in the United Kingdom

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