User Guide: Groundwater Vulnerability (Scotland) GIS dataset
Contents
1. Any individuals or bodies involved in the activities listed in Section 2 3 are likely to find the groundwater vulnerability dataset useful OR 11 064 Groundwater Vulnerability Scotland E gt 4a E 4b ie 2 a BB not available Figure 1 The groundwater vulnerability Scotland map Version 2 OR 11 064 Table 1 Groundwater vulnerability classifications and their interpretation Vulnerability Description Frequency of Travel class activity time 5 Vulnerable to most pollutants with rapid impact Hic Gao Vulnerable to Rapid Vulnerable to 4a May have low permeability individual those soil less likely to have clay events 4 pollutants not present in superficial deposits dil EA 4b More likely to have clay adsorbed or mas itansf rmed present in superficial deposits 3 Vulnerable to some pollutants many others significantly attenuated 2 Vulnerable to some pollutants but only when they are continuously discharged leached Only vulnerable to conservative pollutants in the long term when continuously and widely discharged leached 1 Vulnerable only to Very persistent slow activity Not sufficient data to classify vulnerability e g below lochs in urban areas 0 where geological and or soils data are missing where superficial deposits are mapped but not classified or in mined including opencast and quarried areas 3 Technical Information 3 1 DEFINITIONS Gr2. 27 AND Bedrock Flow type Intergranular or Mixed Vulnerability Attributed according to Table A6 using Bedrock Permeability and Depth to Water in Bedrock 7 Intergranular bedrock with soil cover no superficial deposits mapped Selection Remaining polygons where HOST CLASS IS NOT 22 OR 27 AND Bedrock Flow type Intergranular or Mixed Vulnerability If HOST Class Group A Class 9 16 18 24 26 28 or 29 low permeability soil then Vulnerability is attributed according to Table A8 using Bedrock Permeability and Depth to Water in Bedrock Otherwise if HOST Class Group B all other HOST classes high or moderate permeability soil then Vulnerability is attributed according to Table A7 using Bedrock Permeability and Depth to Water in Bedrock 15 OR 11 064 Appendix 3 Tables for vulnerability classification These tables are used with the rules in Section 3 to define the assigned vulnerability class for each given combination of input parameters They have been slightly modified from the tables used to derive Version 1 of the groundwater vulnerability dataset Ball et al 2004 as follows Vulnerability Class 4 has been subdivided throughout into two sub classes Class 4a and Class 4b Class 4a includes areas where superficial deposits have low permeability Class 4b includes areas where superficial deposits have moderate or high permeability The tables have been amended to reflect this Because of this c
3. Because of this the permeability of all has been classed as ranging from low minimum to moderate maximum Only in areas which have been remapped using modern techniques are the lithologies of these deposits described in more detail for example where hummocky moundy glacial deposits are described as comprising gravel and sand only and these deposits are classed as having high permeability In Version 1 till was treated separately from moraine and hummocky moundy deposits but this set up a false division between mapped till and moraine which in reality cannot be distinguished It therefore also gave a false impression of the accuracy of the map To promote consistency as well as transparency and given this available level of detail and accuracy in the available geological mapping for Version 2 of the groundwater vulnerability dataset the permeability of all glacial deposits as for all other superficial deposits has been taken directly from the latest version of the BGS Permeability Dataset of Great Britain Version 6 2010 e Soil permeability James Hutton Institute formerly the Macaulay Institute O Soil permeability derived from HOST data was used to refine the vulnerability classification for areas where BGS maps show no superficial deposits Where no superficial deposits are mapped and the HOST classes is one of 9 16 18 24 26 28 or 29 which all refer to low permeability soils the vulnerability classifi
4. of Scotland Figure 2 OR 11 064 Figure 2 The coverage of the groundwater vulnerability Scotland dataset 3 7 DATA FORMAT The groundwater vulnerability Scotland Version 2 dataset is available as both a vector dataset and a raster dataset Both datasets contain only the final groundwater vulnerability classification and none of the input parameter information Table 3 Table 1 The raster dataset has a 50 m grid cell size with the grid value equal to the groundwater vulnerability classification Table 1 Table3 Data fields and parameter values in the aquifer productivity datasets Field Description Values Vuln Groundwater vulnerability As Table 1 4 Licensing Information The British Geological Survey does not sell its digital mapping data to external parties Instead BGS grants external parties a licence to use this data subject to certain standard terms and conditions In general a licence fee will be payable based on the type of data the number of users and the duration years of a licence OR 11 064 All recipients of a licence potential licensees are required to return a signed digital data licence document to us before authorisation for release of BGS digital data is given In general terms a BGS digital data licensee will be permitted to make internal use of the dataset s allow a specified number of internal users to access use the data the number of users will be ag
5. records but modified applying expert knowledge to particular areas For more information see Ball et al 2004 CLAY Delineating those areas known to contain at least Derived from lithological log data 5m thickness of clay within the superficial deposits held in BGS s Single Onshore sequence either as a single unit or the sum of more Borehole Index SOBI database For than one unit more information see Ball et al 2004 SD_DTW Depth to groundwater level in superficial deposits Developed by BGS for the purposes aquifers This dataset is based primarily on a of the groundwater vulnerability surface representing the depth from ground level to map For more information see the river base level which is modelled based on a Appendix 1 and Ball et al 2004 digital terrain model DTM and the locations of major rivers combined with HOST data showing areas where the water table is lt 2m Four classes of depth to groundwater level are defined 1 lt 3m 2 3 10m 3 10 30m and 4 gt 30m BR_DTW Depth to groundwater level in bedrock aquifers Developed by BGS for the purposes This is defined only for aquifers with significant intergranular flow Four classes of depth to groundwater level are defined 1 lt 3m 2 3 10m 3 10 30m and 4 gt 30m of the groundwater vulnerability map OR 11 064 Parameter name Description Dataset derivation HOST_CLASS HOST Hydrology of Soil T
6. relative contamination under conditions of uncertainty National Research Council US Committee on Techniques for Assessing Groundwater Vulnerability National Academy Press 10 OR 11 064 Appendix 1 Detail of amendments to input datasets compared to Version 1 The input datasets used to produce Version 2 of the groundwater vulnerability dataset are listed and described briefly in Table 2 More detail on how they have been amended from Version 1 of the groundwater vulnerability dataset is given here The derivation ownership of the input datasets is given in brackets after the name of each dataset For more detail on the original derivation of these datasets for Version 1 see Ball et al 2004 e DiGMapGB 50 BGS O DiGMapGB 50 the Digital Geological Map of Great Britain at 1 50 000 scale for bedrock and superficial deposits are the key input datasets These have been significantly revised since Version 1 of the groundwater vulnerability dataset was produced Version 5 18 was used during the creation of the vulnerability map For a few parts of Scotland DiGMapGB 50 is not available for superficial deposits and in these cases superficial geology data at 1 625 000 scale has been merged in e Permeability of bedrock and superficial geological units BGS O This has been taken from the latest versions of BGS s Permeability Datasets for Great Britain Version 6 2010 for bedrock and superficial deposits which have been revise
7. 0 30 gt 30 Superficial deposits permeability at surface VH or H Table A6 Bedrock Flow Type Significantly Intergranular including mixed fracture intergranular no soil or superficial deposits Rule 6 Depth to Water in Bedrock m 0 3 3 10 10 30 30 Bedrock permeability VHor H 17 OR 11 064 Table A7 Bedrock Flow Type Significantly Intergranular including mixed fracture intergranular no superficial deposits high or moderate soils HOST classes in Group B see Rule 7 Depth to Water in Bedrock m 0 3 3 10 10 30 30 Bedrock permeability VH orH M L Table A8 Bedrock Flow Type Significantly Intergranular including mixed fracture intergranular no superficial deposits low permeability soils HOST classes in Group A see Rule 7 Depth to Water in Bedrock m 0 3 3 10 10 30 30 VH or H Bedrock permeability M E Table A9 Bedrock Flow Type Significantly Intergranular including mixed fracture intergranular Superficial Deposits Permeability at surface Very High or High Rule 5 Depth to Water Bedrock High permeability superficial deposits thickness m in Bedrock m perm gt 5m cla eability g in y sequence VH or H VH or H 18 OR 11 064 Table A10 Bedrock Flow Type Significantly Intergranular including mixed fracture intergranular Superficial Deposits Permeability at sur
8. British Geological Survey NATURAL ENVIRONMENT RESEARCH COUNCIL User Guide Groundwater Vulnerability Scotland GIS dataset Version 2 Groundwater Science Programme Open Report OR 1 1 064 BRITISH GEOLOGICAL SURVEY GROUNDWATER SCIENCE PROGRAMME OPEN REPORT OR 11 064 User Guide Groundwater Vulnerability Scotland GIS dataset Version 2 The National Grid and other Ordnance Survey data are used with the permission of the Controller of Her Majesty s Stationery Office Licence No 100017897 2011 Keywords Groundwater vulnerability Scotland GIS Front cover Groundwater vulnerability Scotland mao Bibliographical reference DOCHARTAIGH B DOcE D D RUTTER H K AND MACDONALD A M 2011 User Guide Groundwater Vulnerability Scotland GIS dataset Version 2 British Geological Survey Open Report OR 11 064 25pp Copyright in materials derived from the British Geological Survey s work is owned by the Natural Environment Research Council NERC and or the authority that commissioned the work You may not copy or adapt this publication without first obtaining permission Contact the BGS Intellectual Property Rights Section British Geological Survey Keyworth e mail ipr bgs ac uk You may quote extracts of a reasonable length without prior permission provided a full acknowledgement is given of the source of the extract Maps and diagrams in this book use topography base
9. ally based classification of the soils of the United Kingdom Institute of Hydrology Report No 126 Institute of Hydrology Wallingford British Geological Survey 2010 Permeability Indices PI data Information Note 2010 Permeability Index Version 6 0 British Geological Survey Information Note Accessed from http www bgs ac uk products hydrogeology permeability html 11 October 2011 Foster S S D 1998 Groundwater recharge and pollution vulnerabiloity of British aquifers a critical review In Robins N S ed Groundwater Pollution Aquifer Recharge and Vulnerability Special Publications 130 Geological Society London 7 22 Lawley R and Garcia Bajo M 2009 The National Superficial Deposit Thickness Model version 5 British Geological Survey Internal Report OR 09 049 MacDonald A M Ball D F and O Dochartaigh B E 2004 A GIS of aquifer productivity in Scotland explanatory notes BGS Commissioned Report CR 04 047N Dochartaigh B Ball D F MacDonald A M Lilly A Fitzsimons V del Rio M and Auton C A 2005 Mapping groundwater vulnerability in Scotland a new approach for the Water Framework Directive Scottish Journal of Geology 41 1 21 30 Dochartaigh B Doce D D Rutter H K and MacDonald A M 2011 User Guide British Geological Survey Aquifer Productivity Scotland GIS datasets Version 2 BGS Internal Report OR 1 1 065 US National Research Council 1993 Groundwater vulnerability assessment predicting
10. at used for Version 1 The method is described in detail in Appendices 2 and 3 3 4 INPUT DATASETS The input datasets used to produce Version 2 of the dataset are listed and described briefly in Table 2 More detail on how they have been amended from Version 1 is given in Appendix 1 Table 2 Data fields and parameter values used in the creation of the groundwater vulnerability Scotland Version 2 map input datasets and final groundwater vulnerability class Parameter name Description Dataset derivation BR_FLOWTYPE Flow type flow mechanism in bedrock aquifers Significantly Intergranular mixed Intergranular Fracture or Fracture From BGS s Bedrock Aquifer Productivity Scotland map O Dochartaigh et al 2011 BR_MAXPERM Maximum permeability of bedrock Very High High Moderate Low or Very Low From BGS s Permeability Dataset for Great Britain Bedrock British Geological Survey 2010 SD_MAXPERM Maximum permeability of superficial deposits Very High High Moderate Low or Very Low From BGS s Permeability Dataset for Great Britain Superficial Deposits British Geological Survey 2010 SD_THICK Superficial deposits are only mapped where gt 1m Based on the first version of BGS s thick Thickness of superficial deposits was coded superficial deposits thickness map as follows 1 1 3m 2 3 10m 3 10 30m 4 which was interpolated from gt 30m borehole
11. cation is reduced 12 OR 11 064 e Soil thickness James Hutton Institute formerly the Macaulay Institute BGS O Soil thickness derived from HOST data in combination with superficial deposits mapping was used to distinguish areas where essentially bare rock is exposed at the ground surface Where the HOST class is either 22 or 27 which both refer to very thin soils the vulnerability classification is increased e Depth to groundwater level in superficial deposits BGS O An updated map of depth to groundwater in superficial maps has been produced for Version 2 of the groundwater vulnerability map using updated input data This map is based primarily on a surface representing the depth from ground level to the river base level which is modelled based on a digital terrain model DTM and the locations of major rivers This surface is termed the River Head Space Bloomfield et al 2007 It was recreated for Version 2 using the NextMap DTM instead of the Ordnance Survey DTM used for Version 1 The same digital river network from SEPA was used as for Version 1 The River Head Space surface was converted to a vector file with four depth to groundwater classes lt 3m 3 10m 10 30m and gt 30m This was then combined with HOST soils data which show soils where the groundwater table is lt 2m taken as HOST classes 10 and 12 including these areas in the River Head Space lt 3m category Where the HOST data show the water table i
12. cotland Dataset Version 2 2 1 BACKGROUND The groundwater vulnerability Scotland dataset Version 1 was produced in 2004 by the British Geological Survey BGS and the Macaulay Institute now the James Hutton Institute on behalf of the Scottish Environment Protection Agency SEPA funded by the Scotland and Northern Ireland Forum for Environmental Research SNIFFER The dataset comprised a GIS based groundwater vulnerability screening tool and an associated report describing the groundwater vulnerability screening methodology Ball et al 2004 O Dochartaigh et al 2005 This revised version Version 2 uses updated input data and a slightly modified methodology to develop new GIS based maps Related BGS datasets that the user may also be interested in are maps of bedrock and superficial deposits aquifer productivity for Scotland O Dochartaigh et al 2011 MacDonald et al 2004 permeability index datasets British Geological Survey 2010 superficial deposits thickness datasets Lawley and Garcia Bajo 2009 and DiGMapGB 50 the Digital Geological Map of Great Britain at 1 50 000 A related external dataset is the Hydrology of Soil Types HOST available through the James Hutton Institute Boorman et al 1995 http www macaulay ac uk host 2 2 WHAT THE DATASET SHOWS The groundwater vulnerability dataset is a screening tool that shows the relative threat to groundwater quality across Scotland from contamination Groundwater v
13. d on Ordnance Survey mapping NERC 2011 All rights reserved Keyworth Nottingham BEO Dochartaigh D D Doce H K Rutter and A M MacDonald British Geological Survey 2011 BRITISH GEOLOGICAL SURVEY The full range of our publications is available from BGS shops at Nottingham Edinburgh London and Cardiff Welsh publications only see contact details below or shop online at www geologyshop com The London Information Office also maintains a reference collection of BGS publications including maps for consultation We publish an annual catalogue of our maps and other publications this catalogue is available online or from any of the BGS shops The British Geological Survey carries out the geological survey of Great Britain and Northern Ireland the latter as an agency service for the government of Northern Ireland and of the surrounding continental shelf as well as basic research projects It also undertakes programmes of technical aid in geology in developing countries The British Geological Survey is a component body of the Natural Environment Research Council British Geological Survey offices BGS Central Enquiries Desk Tel 0115 936 3143 email enquiries bgs ac uk Fax 0115 936 3276 Kingsley Dunham Centre Keyworth Nottingham NG12 5GG Tel 0115 936 3241 Fax 0115 936 3488 email sales bgs ac uk Murchison House West Mains Road Edinburgh EH9 3LA Tel 0131 667 1000 Fax 0131 668 2683 email scotsales bgs ac u
14. d since Version 1 These datasets define both a minimum and a maximum permeability for each geological formation to encompass the likely range of permeability for any one formation both because of the natural heterogeneity of geological formations e g the presence of siltstone or mudstone bands within a dominantly sandstone sequence and because of the lack of measured permeability data available for most formations and therefore the uncertainty in ascribing a single permeability value For the purposes of the vulnerability assessment a cautionary approach was taken in that the maximum possible permeability is the most relevant since this defines the worst case scenario in terms of groundwater vulnerability For the purposes of the vulnerability map a small number of changes were made to the bedrock permeability classifications in the latest version of BGS s Permeability Dataset for Great Britain in those cases where new information e g from test pumping has become available since the dataset was last revised or where errors were noted The superficial deposits permeability classifications in the latest version of BGS s Permeability Dataset for Great Britain have been used directly in the production of the groundwater vulnerability dataset with no changes A number of classifications in this dataset are recognised as being potentially wrong on a local scale either because of the level of available detail and accuracy in the geological map
15. dataset is a screening tool that provides specific information on the vertical pathway to the water table It is not a complete solution to groundwater risk assessment and site suitability studies It can provide guidance on the vulnerability of groundwater at a regional scale highlighting areas at comparatively higher risk of groundwater contamination and can help indicate the level of specific site investigation required for a new development or activity Groundwater vulnerability maps provide information on the pathway followed by pollutants resulting from human activities e g related to industrial urban agricultural or domestic practices to the water table They are used along with an assessment of the hazard and of the consequences of pollution occurring to help calculate the degree of risk of contamination caused by such activities The dataset allows for regional assessment of groundwater vulnerability as one stage in the process of assessing overall risk to groundwater for example when combined with land use and aquifer maps The dataset may have several uses including In policy analysis and development To prioritise aquifer and site investigations To inform planning decisions To improve awareness of groundwater in general 2 4 LIMITATIONS The groundwater vulnerability Scotland Version 2 dataset has been developed at 1 100 000 scale and must not be used at larger scales It is not designed to assess g
16. evised on a periodic rather than on an annual basis licensees will therefore not automatically receive a new dataset each year unless changes have been made to the data These are general comments for guidance only A licensee of BGS s digital data is provided with full details of the basis on which individual BGS datasets licensed to them are supplied If you have any doubts about whether your proposed use of the BGS data will be covered by a BGS digital licence the BGS Intellectual Property Rights IPR section will be happy to discuss this with you and can be contacted through the following email address iprdigital bgs ac uk BGS IPR will usually be able to provide reassurance that the licence will cover individual user requirements and or to include additional special conditions in the licence documentation addressing specific requirements within BGS s permitted usage References Ball D MacDonald A Dochartaigh B del Rio M FitzSimons V Auton C and Lilly A 2004 Development of a groundwater vulnerability screening methodology for the Water Framework Directive SNIFFER Report Project WFD28 BGS Commissioned Report CR 03 294C Bloomfield J P McKenzie A A Rutter H K and Hulbert A 2007 Methodology for mapping geological controls on susceptibility to groundwater flooding British Geological Survey Internal Report IR 07 72 55pp OR 11 064 Boorman D B Hollis J M and Lilly A 1995 Hydrology of soil types a hydrologic
17. face Moderate Rule 5 Depth to Water Bedrock Moderate permeability superficial deposits thickness m in Bedrock m perm eability gt 5m clay in sequence Table A11 Bedrock Flow Type Significantly Intergranular including mixed fracture intergranular Superficial Deposits Permeability at surface Low Rule 5 Bedrock Low permeability superficial deposits thickness m Depth to Water perm in Bedrock m ability 1 RACEN VH or H a a 19
18. hange one table the original Table 2 has been removed as no longer needed The following abbreviations and legend are used in the tables VH Very High permeability H High permeability M Moderate permeability L Low permeability n a not applicable Vulnerability class Highest Lowest Table A1 Bedrock Flow Type Fractured no soil or superficial deposits mapped Rule 3 Fractured bedrock no soil or superficial deposits Fractured bedrock no soil or superficial deposits Table A2 Bedrock Flow Type Fractured soil present no superficial deposits mapped Rule 4 Superficial deposits thickness m lt 1 Soil permeability OR 11 064 Table A3 Bedrock Flow Type Fractured superficial deposits are mapped Clay Thickness lt 5m Rule 2 Superficial deposits thickness m 1 3 3 10 10 30 gt 30 VH or H Superficial deposits M permeability at surface Table A4 Bedrock Flow Type Fractured superficial deposits are mapped Clay Thickness gt 5 m Rule 2 Superficial deposits thickness m Superficial deposits permeability at surface Table A5 Superficial Deposits Permeability at surface High or Very High there is a water table in superficial deposits Superficial Deposits Thickness gt Depth to Water in Superficial Deposits Rule 1 Depth to Water in Superficial Deposits m lt 3 3 10 1
19. i n sssini essea 5 Dale Defin oNSsisen cates ste cece lesa i aee a eseis ais 5 Dede Sealers estaas tien nesia eta bead ees eee be cee EEO EO ee eee 5 3 3 Methodology used to create Dataset bse sei ccsscasck xasyeues cadenesesec aucaeaand dude tdecanchaecomnacansbaanes 5 3 4 Input Datasets ei i3scksxisccaeendeaesssascaninasohea ss oda ianaeeed dads Sopvad anced a sind odds Sena eee eta 6 3 3 A DALASSLISLOLY nis SvenriscdaSerghus uetonceatadeeentsaneacdste nylon aeea ae atea etes a e aa 7 3 0 Coyetag eripi ie beets aaa ea sopaateaaunte sea Sos ae saan addy saseaetaabicsu AATE i Dod Data Format arec openii an i E tat race hs E E E tee ahaa ta atorat iad 8 4 Licensing Information sssssissiscsoiesrscoireissseshensseecosieescsisrosseoneis sooo ccpaedeunsdeevensesiuceutencaserauneseas 8 REFERER CES aessa a aes aeaea E EE E sS e seraa 9 Appendix 1 Detail of amendments to input datasets compared to Version 1 11 Appendix 2 Methodology used to create vulnerability dataset cccssccsssscssssscesseees 14 Appendix 3 Tables for vulnerability classification ccscccssssccssssccsssscssssccssscsssssssssees 16 FIGURES Figure 1 The groundwater vulnerability Scotland map Version 2 0 0 0 eesceseeeeeeeeneeeeeeeees 4 Figure 2 The coverage of the groundwater vulnerability Scotland dataset ee eee eeee 8 TABLES Table 1 Groundwater vulnerability classifications and their interpretation 0 0 0 0 cee eeeee 5 Table 2 Data f
20. ields and parameter values used in the creation of the groundwater vulnerability Scotland Version 2 map input datasets and final groundwater vulnerability class 6 Table 3 Data fields and parameter values in the aquifer productivity datasets eeceeeeeees 8 OR 11 064 Summary This report describes a revised version Version 2 of the groundwater vulnerability Scotland digital dataset produced by the British Geological Survey BGS Version 1 of the dataset was produced in 2004 by the British Geological Survey BGS and the Macaulay Institute now the James Hutton Institute on behalf of the Scottish Environment Protection Agency SEPA funded by the Scotland and Northern Ireland Forum for Environmental Research SNIFFER Version 2 uses updated input data and a slightly modified methodology The map shows the relative vulnerability of groundwater to contamination across Scotland Groundwater vulnerability is the tendency and likelihood for general contaminants to move vertically through the unsaturated zone and reach the water table after introduction at the ground surface On this map groundwater vulnerability is described by one of five relative classes ranging from 1 lowest vulnerability to 5 highest vulnerability The groundwater vulnerability map is a screening tool that can be used to show the relative threat to groundwater quality from contamination across Scotland It can provide guidance on the vulnerability of ground
21. k Natural History Museum Cromwell Road London SW7 5BD Tel 0207589 4090 Fax 020 7584 8270 Tel 020 7942 5344 45 email bgslondon bgs ac uk Columbus House Greenmeadow Springs Tongwynlais Cardiff CF15 7NE Tel 029 2052 1962 Fax 029 2052 1963 Maclean Building Crowmarsh Gifford Wallingford OX10 8BB Tel 01491 838800 Fax 01491 692345 Geological Survey of Northern Ireland Colby House Stranmillis Court Belfast BT9 5BF Tel 028 9038 8462 Fax 028 9038 8461 www bgs ac uk gsni Parent Body Natural Environment Research Council Polaris House North Star Avenue Swindon SN2 1EU Tel 01793 411500 Fax 01793 411501 www nerc ac uk Website www bgs ac uk Shop online at www geologyshop com OR 11 064 Contents COMM ENS S EEEE E I E E E EE EEE i SUMMATY iesse iasss ripasso n orii ea S iaa eves cunssuenouasewai oun TSKCS SERTEL E a EEEn E rar ais ii 1 Introduction cs cecan gatcnaesassceccasnsdansdicenctencaesccetnsstoncansscucatasoumedegiescsedanesuea eneseaatosnencaegsbonstaaseoneese 1 2 The Groundwater Vulnerability Scotland Dataset Version 2 csccccsssccsssscesssscesees 1 2i Background anana a a E a N a a a 1 2 2 What the dataset Shows rieme snie meinn a e ede ea a Bends 1 23 Howcan the dataset De Used Tis onn a a a RG A EA A ea 2 DA Limitations aea a a a a E Manco tate 2 2 5 Who might benefit from using the dataset eseeeeeeseseeseeseessesreesersrrseresressrseresresseserss 3 3 Technical Informat
22. meability low permeability soils reduce vulnerability from 5 to 4a Selection Remaining polygons where HOST Class IS NOT 22 OR 27 AND Bedrock Flow type Fractured 14 OR 11 064 Vulnerability If HOST Class Group A Class 9 16 18 24 26 28 or 29 low permeability soil then Vulnerability 4a from Table A2 Otherwise Vulnerability 5 5 Intergranular bedrock superficial cover Selection Remaining polygons with Bedrock Flow type Intergranular or Mixed AND superficial deposits are mapped Vulnerability If Clay Thickness gt 5m then Vulnerability 1 Tables A9 A10 and A11 If Clay Thickness lt 5m AND Superficial Deposits Permeability Very High or High then Vulnerability is attributed according to Table A9 using Depth to Water in Bedrock Bedrock Permeability and Superficial Deposits Thickness If Clay Thickness lt 5m AND superficial permeability Moderate then Vulnerability is attributed according to Table A109 using Depth to Water in Bedrock Bedrock Permeability and Superficial Deposits Thickness If Clay Thickness lt 5m AND Superficial Deposits Permeability Low or Very Low then Vulnerability is attributed according to Table All using Depth to Water in Bedrock Bedrock Permeability and Superficial Deposits Thickness 6 Intergranular bedrock with no cover no superficial deposits mapped and soil is effectively absent Selection Remaining polygons where HOST Class 22 OR
23. most realistic superficial deposits thickness model for Scotland at 1 50 000 scale e Presence of thick clays in the superficial deposits sequence BGS O This dataset is unchanged from Version 1 13 OR 11 064 Appendix 2 Methodology used to create vulnerability dataset The groundwater vulnerability dataset was produced in ArcGIS by combining a range of environmental datasets Table 2 A detailed description of the methodology for developing the groundwater vulnerability Version dataset is given in Ball et al 2004 This new dataset Version 2 was produced along largely the same lines with some small methodological changes to simplify the assessment procedure but using updated input datasets The input datasets used to produce Version 2 of the dataset are listed and described briefly in Table 2 More detail on how they have been amended from Version 1 is given in Appendix 1 A rule based method for combining the various input datasets to define a vulnerability classification has been used which has been modified only slightly from that used for Version 1 The method is described by a set of scenarios and a corresponding set of rules or criteria which are implemented on the input datasets in turn depending on whether a particular scenario is true As each rule is implemented parts of the map i e polygons in the GIS file are selected and these selected polygons are attributed with the relevant vulnerability classificatio
24. n as shown in a set of tables which are shown in Appendix 2 Once each rule has been implemented the polygons already attributed are excluded and the next rule is implemented The scenarios considered and the rules implemented in order with the input datasets used for each are as follows 1 Superficial deposits at the ground surface are highly permeable and water table is in the superficial deposits Selection Polygons where Superficial Deposits Permeability High or Very High and Superficial Deposits Thickness gt Depth to Water in Superficial Deposits Vulnerability Attributed according to the values in Table A5 using the datasets Superficial Deposits Permeability and Depth to Water in Superficial Deposits 2 Fractured bedrock superficial cover Selection Remaining polygons with Bedrock Flow type Fractured AND superficial deposits are mapped Vulnerability If Clay Thickness gt 5m then Vulnerability 1 from Table A4 If Clay Thickness lt 5m then Vulnerability is attributed according to Table A3 using Superficial Deposits Permeability and Superficial Deposits Thickness 3 Fractured bedrock no cover no superficial deposits mapped and soil is effectively absent Selection Remaining polygons where HOST Class 22 OR 27 AND Bedrock Flow type Fractured Vulnerability Vulnerability 5 from Table A1 4 Fractured bedrock soil cover no superficial deposits mapped Subdivided according to soil per
25. onship between high permeability and high aquifer productivity For Version 1 of the groundwater vulnerability dataset much focus was put into the subdividing of till deposits according to their likely permeability This approach has been simplified for Version 2 For Version 1 the permeability of till deposits was subdivided using HOST and supporting soil parent material data to define three till subclasses highly permeable tills derived from Precambrian rocks and classed as local aquifers moderately permeable tills derived largely from Devonian sandstones in Strathmore and low permeability tills largely derived from Carboniferous sedimentary rocks in central Scotland Ball et al 2004 This approach has been revised partly because it is no longer thought that any tills are highly permeable and partly because of the level of available detail and accuracy in superficial deposits mapping Superficial deposits were historically often mapped in less detail and or with less precision than bedrock formations The level of detail and accuracy in the current maps of glacial deposits mean it is not possible to accurately distinguish between till moraine and hummocky moundy glacial deposits although recent evidence suggests that moraine is typically significantly more permeable than till The lithology of most of these glacial deposits is described interchangeably as diamicton or some mix of diamicton silt clay sand and gravel
26. oundwater vulnerability is the tendency and likelihood for general contaminants to move vertically through the unsaturated zone and reach the water table after introduction at the ground surface It therefore accounts for intrinsic properties of the vertical pathway in the unsaturated zone above the water table whether within an aquifer or its overburden superficial deposits and or soil It does not account for the movement of contaminants through the saturated zone of an aquifer after reaching the water table 3 2 SCALE The groundwater vulnerability Scotland Version 2 dataset is produced for use at 1 100 000 scale The dataset is not designed to be used to assess groundwater vulnerability at a single point All spatial searches of the map dataset should be conducted using a minimum 100 m buffer 3 3 METHODOLOGY USED TO CREATE DATASET The groundwater vulnerability dataset was produced in ArcGIS by combining a range of environmental datasets Table 2 A detailed description of the methodology for developing the groundwater vulnerability Version dataset is given in Ball et al 2004 This new dataset Version 2 was produced along largely the same lines with some small methodological changes to simplify the assessment procedure but using updated input datasets 5 OR 11 064 A rule based method for combining the various input datasets to define a vulnerability classification has been used which has been modified only slightly from th
27. ping or because of the natural heterogeneity of geological formations in particular superficial deposits As has been discussed in the user notes for the associated aquifer productivity maps Scotland O Dochartaigh et al 2011 classifying superficial deposits aquifers on a national scale is subject to much uncertainty and must of necessity involve simplification generalisation and therefore the masking of local variations Because this groundwater vulnerability dataset is also made on a national scale it is accepted that the same approach of simplification must be made These points in particular however are made The permeability of superficial deposits refers only to the superficial deposits mapped at the ground surface The permeability of any different superficial deposits at depth in the superficial deposits sequence has not been taken into 11 OR 11 064 account EXCEPT where it is known that at least 5m thickness of clay exists within the sequence The permeability of superficial deposits has been used both to help define the productivity of superficial deposits aquifers and as an input into the groundwater vulnerability map in its own right However aquifer permeability and productivity are different things so that for example geological formations may have high permeability but do not form productive aquifers perhaps because they are too thin or of too small a lateral extent There is not necessarily a direct relati
28. reed with the licensee and specified in the licence document for the purposes of their day to day internal activities reproduce extracts from the data up to A3 for use in external analogue paper hard copy or non queryable electronic e g secured pdf format to meet a public task duty fulfil a statutory requirement and or as part of academic or other non commercial research But will not be permitted to provide a bureau service for others or incorporate the data in the generation of products or services for commercial purposes sell assign sublicense rent lend or otherwise transfer any part of the dataset s or the licence place any part of the dataset s on the Internet The BGS is committed to ensuring that all the digital data it holds which is released to external parties under licence has been through a robust internal approval process to ensure that geoscientific standards and corporate quality assurance standards are maintained This approval process is intended to ensure that all data released i is quality assured ii meets agreed BGS data management standards iii is not in breach of any 3rd party intellectual property rights or other contractual issues such as confidentiality issues that would mean that release of the data is not appropriate When the BGS digital datasets are revised any upgrades will be automatically supplied to the licensee at no additional cost Geological map datasets are r
29. roundwater vulnerability at a single point All spatial searches against the data should therefore be conducted using a minimum 100 m buffer The groundwater vulnerability Scotland Version 2 dataset is based on and limited to an interpretation of the records in the possession of the British Geological Survey at the time the dataset was created Groundwater vulnerability maps provide approximate descriptions of ground conditions Use of them must therefore be pragmatic The US National Research Council 1993 quotes three laws of groundwater vulnerability which are instructive when using any groundwater vulnerability map 1 All groundwater is to some degree vulnerable 2 Uncertainty is inherent in all vulnerability assessments 3 There is a risk that the obvious may be obscured and the subtle indistinguishable OR 11 064 2 5 WHO MIGHT BENEFIT FROM USING THE DATASET The groundwater vulnerability dataset was originally developed for use by the Scottish Environment Protection Agency SEPA for protecting and managing groundwater and informing their response to land use planning applications Other potential users of the dataset are regional planners and managers in Local Authorities and national government Identifying areas where groundwater is vulnerable to contamination is a key stage in effective environmental management for example related to sustainable agricultural and industrial practices and land use planning applications
30. s lt 2m and the River Head Space data show it is gt 3m the HOST data takes precedence and the final classification is lt 3m as the HOST data are based on real observations while the River Head Space map is based on an unverified model e Depth to groundwater level in bedrock aquifers BGS O Depth to groundwater in bedrock aquifers is defined only for aquifers with significant intergranular flow This has been changed slightly from Version 1 because the bedrock aquifer flow type classifications in the bedrock aquifer productivity map Dochartaigh et al 2011 have been updated Depth to groundwater has been added for one other bedrock aquifer unit the Glenvale Sandstone Formation west of Dundee which was previously classed as having mixed intergranular fracture groundwater flow but has been reclassified as having significantly intergranular flow Where no groundwater level data are available for a bedrock unit with significantly intergranular flow the depth to groundwater map defaults to the shallowest category lt 3 m as the conservative scenario i e worst case in terms of groundwater vulnerability e Superficial deposits thickness BGS O This dataset is unchanged from Version 1 a version of BGS s Geohazard interpolated model based on borehole data which has been manually corrected by Quaternary geologists in those areas where no borehole data exist This combination of modelling and geological knowledge has provide the
31. ulnerability is a term that has been in use for more than 30 years and has been interpreted in different ways The accepted definition of groundwater vulnerability in the UK and other European countries is the tendency and likelihood for general contaminants to reach the water table within the uppermost aquifer after introduction at the ground surface O Dochartaigh et al 2005 Groundwater vulnerability therefore accounts for intrinsic properties of the vertical pathway in the unsaturated zone above the water table whether within an aquifer or its 1 OR 11 064 overburden All groundwater is to some extent vulnerable to contamination from surface or sub surface sources Foster 1998 and one of the objectives of vulnerability maps is to integrate geological and hydraulic charactersistics of aquifers and overlying material to indicate the relative risk to groundwater from contamination The groundwater vulnerability dataset does not account for the movement of contaminants through the saturated zone of an aquifer after reaching the water table Separate aquifer productivity maps have been developed to help characterise this pathway O Dochartaigh et al 2011 The groundwater vulnerability map Scotland is shown in Figure 1 Groundwater vulnerability is described by one of five relative classes ranging from 1 lowest vulnerability to 5 highest vulnerability Table 1 2 3 HOW CAN THE DATASET BE USED The groundwater vulnerability
32. water at a regional scale highlighting areas at comparatively higher risk of groundwater contamination and can help indicate the degree of specific site investigation required for a new development or activity It is designed to be used at a scale of 1 100 000 and should be regarded as a tool to aid groundwater risk assessment rather than a complete solution ii OR 11 064 1 Introduction Founded in 1835 the British Geological Survey BGS is the world s oldest national geological survey and the United Kingdom s premier centre for earth science information and expertise The BGS provides expert services and impartial advice in all areas of geoscience Our client base is drawn from the public and private sectors both in the UK and internationally Our innovative digital data products aim to help describe the ground surface and what s beneath across the whole of Great Britain These digital products are based on the outputs of the BGS survey and research programmes and our substantial national data holdings This data coupled with our in house Geoscientific knowledge are combined to provide products relevant to a wide range of users in central and local government insurance and housing industry engineering and environmental business and the British public Further information on all the digital data provided by the BGS can be found on our website or by contacting one of our offices or enquiries bgs ac uk 2 The Groundwater Vulnerability S
33. ypes Class Digital soils data at From the James Hutton 1 250 000 scale Institute formerly the The following groups of HOST classes were used at Macaulay Saute 7 A lt a Boorman et al 1995 different stages of creating the groundwater vulnerability mapi http www macaulay ac uk f host HOST class 9 16 18 24 26 28 or 29 to define low permeability soils HOST class 22 or 27 to define thin soils HOST class 10 or 12 to define areas where groundwater is present within 2m of ground level see also below Depth to groundwater level in superficial deposits VULN Code representing relative groundwater vulnerability from 1 very low vulnerability to 5 very high vulnerability See Table 1 for how to interpret the codes 3 5 DATASET HISTORY The groundwater vulnerability Scotland dataset Version 1 was produced in 2004 by the British Geological Survey BGS and the Macaulay Institute now the James Hutton Institute on behalf of the Scottish Environment Protection Agency SEPA funded by the Scotland and Northern Ireland Forum for Environmental Research SNIFFER The dataset comprised a GIS based groundwater vulnerability screening tool and an associated report describing the groundwater vulnerability screening methodology Ball et al 2004 This revised version Version 2 uses updated input data and a slightly modified methodology to develop new GIS based maps 3 6 COVERAGE The dataset covers all
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