Groundwater Vulnerability National Dataset User Guide

Transcription

1 Groundwater Vulnerability National Dataset User Guide Version st January 2009

2 Contents 1.0 Record of amendment Introduction Description of the Groundwater Vulnerability Related data sources Public Register and non Public Register Data National Security Legislation relevant to GWV Data structure Data quality Data Standards Reporting errors Validation rules and completeness checks Validation checks specific to the Ground Water data Known quality issues Frequently Asked Questions (FAQ) Useful information when using the data What is not included in the data Recommendations on how to use or analyse the data Changes in the data Change in dataset name Glossary Feedback form Appendix Appendix 2: Soil vulnerability classification Soils of High Leaching Potential (H) Soils of Intermediate Leaching Potential (I) Soils of Low Leaching Potential (L)...14

3 1.0 Record of amendment Version number Section number Amendment description Date All Amendment of dataset name 01/01/09 Copyright Environment Agency 3

4 2.0 Introduction This document provides information to accompany the Environment Agency s groundwater vulnerability (GWV) dataset. It can be used to gain a better understanding of the GWV when used in conjunction with the current data release. For information relating to national datasets in general; please refer to the National Dataset Generic Text document. Details of our distribution policy can be found in the National Dataset Generic Text document, along with contact details for the Data Management Team. Information about our web site can also be found in the Generic document. The Ground Water web site is located at: This page includes links to other water resources information. 2.1 Description of the Groundwater Vulnerability The Agency has produced a series of maps to broadly define areas relevant to the protection of groundwater. These are based on the maps and concepts that are described in a document known as the Policy and Practice for the Protection of Groundwater (PPPG). This approach considers: the vulnerability of the groundwater resources as a whole; and the specific importance of areas which form the catchments to the main sources of supply. Groundwater resources are assigned a vulnerability class, this is subdivided into major, minor and non-aquifers; soil classification at the surface and presence (if any) of low permeability drift deposits. This dataset of groundwater vulnerability is produced as a separate, published set of fiftythree maps which cover England and Wales. The boundaries on these maps are based on published geological and soil survey mapping. For this reason they are rarely updated, unless re-mapping is carried out. The Groundwater Vulnerability dataset can be used to indicate where groundwater resources may be vulnerable from activities carried out on the surface land. Other information, such as the depth of groundwater and thickness and type of overlying cover, will always be required for a site-specific assessment. The working maps and reports which detail how the GWV have been derived are held at local Agency regional or area offices. The maps are available for inspection. Dissemination and copying of the working maps and reports will be restricted subject to consultation with the relevant local office.. The maps are 1:100,000-km scale and the data type are polygon. The projection is British National Grid. These polygons were created 10/03/1999 and are the result of a joint project between the Environment Agency, British Geological Survey and the Soil Survey and Land Research Centre. Copyright Environment Agency 4

5 2.2 Related data sources The Source Protection Zones (SPZ) dataset shows the parts of aquifers that are considered to form the catchments to public water supplies and certain other private supplies. They provide an indication of the risk to groundwater supplies from potentially polluting activities and accidental releases of pollutants. The National Abstraction Licence Database (NALD) dataset contains details of all live water abstraction licences in England and Wales. The dataset is a static snapshot of NALD, which is a live system and is constantly being updated. For further information on the SPZ and NALD datasets please consult the relevant national dataset user guides. Copyright Environment Agency 5

6 3.0 Public Register and non Public Register Data For a general description of what constitutes public register and non-public register data please refer to the National Dataset Generic Text document. The GWV data is not public register. 3.1 National Security A discussion of national security issues can be found in the Generic Text document. There are no national security issues with any of the fields supplied in GWV. 3.2 Legislation relevant to GWV The Environment Agency is responsible for the protection of controlled waters from pollution under the Water Resources Act Controlled waters includes groundwater. The Act also states that it is an offence to cause pollution of controlled waters, either deliberately or accidentally. The Environment Agency also has specific duties to prevent groundwater pollution by certain dangerous substances under the Groundwater Regulations 1998 and the Waste Management Licensing Regulations The EU Water Framework Directive, implemented through The Water Environment (Water Framework Directive) (England and Wales) Regulations 2003, also requires the adoption of measures to prevent or limit the input of pollutants to groundwater, and for the designation and protection of Drinking Water Protected Areas. Copyright Environment Agency 6

7 4.0 Data structure The data structure of the GWV dataset is given in the National Dataset Field Attribute document. The GWV data is supplied as two shapefiles: GWV_100k: An assessment of the vulnerability of groundwaters to diffuse sources of pollution. This shapefile shows aquifer and soils classifications. The maps identify seven groundwater vulnerability classes, which are based on soil type and underlying geology only. The depth to groundwater is not considered, and the presence of drift is noted, but not incorporated into the assessment. GWV_100k_Drift: An assessment of the vulnerability of groundwaters to diffuse sources of pollution. It shows the distribution of low permeability drift deposits. This dataset should be used in conjunction with the GWV_100k data and a 10k buffer. Copyright Environment Agency 7

8 5.0 Data quality 5.1 Data Standards For data standards applicable to a number of national datasets please consult the National Dataset Generic Text document. Any standards specific to the ground water data are detailed below. 5.2 Reporting errors Methods of reporting errors are included in the Generic Text document. A feedback form can be found at the end of this user guide. 5.3 Validation rules and completeness checks For background information on the data validation process and general completeness checks that we carry out, please refer to the National Dataset Generic Document. 5.4 Validation checks specific to the Ground Water data The maps which form this dataset were created jointly by the Environment Agency, British Geological Survey and Soil Survey, in a one off digitising process and is a static dataset, therefore no data entry validation is required. 5.5 Known quality issues There are minor discrepancies between the digital and paper based maps. The paper maps are more accurate. This data currently has no topology. Copyright Environment Agency 8

9 6.0 Frequently Asked Questions (FAQ) Q: How are the soil vulnerability classes defined? See section 11.0 Appendix 2 for a full explanation, Copyright Environment Agency 9

10 7.0 Useful information when using the data You should take into account the following information when analysing the data. This section also points out information that is not included in the data, as well as any limitations on interpreting the data. An explanatory booklet entitled 'Guide to Groundwater Protection Zones in England and Wales' has been published by The Stationary Office. 7.1 What is not included in the data The paper based Groundwater Vulnerability maps may contain areas with no data. These areas were not digitised. 7.2 Recommendations on how to use or analyse the data Use the.avl file for the legend symbology, to display the different classifications. Please note, the information provided by the groundwater vulnerability maps and source protection maps forms part of an initial screening process in assessing impacts to groundwater resources. A site specific assessment can only be made in conjunction with additional information, including detailed geological and hydrological features, together with consideration of local water use. Site specific assessments can only be made with an appropriate level of expertise in the field. 7.3 Changes in the data The boundaries on these maps are based on published geological and soil survey mapping. For this reason they are rarely updated, unless re-mapping is carried out Change in dataset name Prior to January 2009, this dataset was known as Groundwater Vulnerability Maps. Copyright Environment Agency 10

11 8.0 Glossary GWV IEC NALD PPPG SPZ Ground Water Vulnerability Information Enterprise Centre National Abstraction Licence Database (NALD) Policy and Practice for the Protection of Groundwater Source Protection Zones Copyright Environment Agency 11

12 9.0 Feedback form We welcome feedback on our data. If you have any comments please complete the form below and return to us: Name: Phone: Organisation: Fax: National Dataset. (Please enter dataset to which your feedback relates) Comments: Feedback on contents of documentation: Feedback on data content: General feedback: Information Enterprise Centre Tel: Environment Agency Government Buildings Burghill Road Westbury on Trym Bristol, BS10 6BF Copyright Environment Agency 12

13 10.0 Appendix 1 Complete list of all amendments ever made to the document Version number Section number Amendment description Date All Text reviewed and reformatted 18/04/ Text revised 20/01/ Text revised 20/01/ Text revised 20/01/ Text revised 20/01/ Text revised 20/01/ Text revised 20/01/ Text revised 20/01/ Text from added 20/01/ Section added to /01/ Section removed 20/01/ Section removed 20/01/ Section added 20/01/ Section added 20/01/ Section added 20/01/ Section added 20/01/ Table updated 21/07/ Text Revised 21/07/ Text revised 21/07/ Section re-named NDU Validation rules and completeness 21/07/05 checks Section number changed from to /07/ Text added 21/07/ Section number changed form to /07/ Text revised 21/07/ Section number changed from to /07/ Text Updated 21/07/ Section number changed from to /07/ Section number changed form 5.4. to /07/ Text Updated 21/07/ Section removed 21/07/ Text Updated 21/07/ Table updated 21/07/ Table updated 22/04/ Text Updated 22/04/ Heading Edit 22/04/ Text Updated 22/04/ Text Updated 22/04/ Text Updated 22/04/ Text Updated 22/04/ Text Updated 22/04/ Text Updated 22/04/ Text Updated 22/04/ Table updated 22/04/ Text Updated 22/04/05 Copyright Environment Agency 13

14 11.0 Appendix 2: Soil vulnerability classification The Groundwater Vulnerability maps cover the whole of England and Wales and identify the vulnerability of groundwater to contamination. The maps identify seven groundwater vulnerability classes, which are based on soil type and underlying geology only. Depth to groundwater is not considered, and the presence of drift is noted, but not incorporated into the assessment. The soil vulnerability classification groups the many different soils of England and Wales into three soil vulnerability classes and six sub-classes. Each is based on the physical and chemical properties of soil which affect the downward passage of water and contaminants. These include: texture, structure, soil water regime and the presence of distinctive layers such as raw peaty topsoil and rock or gravel at shallow depth. This classification is not applied to soils above Non-Aquifers Soils of High Leaching Potential (H) This classification is applied to soils with little ability to attenuate diffuse source pollutants and in which non-absorbed diffuse source pollutants and liquid discharges have the potential to move rapidly to underlying strata or to shallow groundwater. They include soils of the Andover, Sherbourne and Sollom Associations from the National Soil Map. Three sub-classes are recognised: H1: Soils that readily transmit liquid discharges because they are either shallow, or susceptible to rapid by-pass flow directly to rock, gravel or groundwater. H2: Deep, permeable, coarse textured soils which readily transmit a wide range of pollutants because of their rapid drainage and low attenuation potential; and H3: Coarse textured or moderately shallow soils which readily transmit non-absorbed pollutants and liquid discharges but which have some ability to attenuate adsorbed pollutants because of their large clay or organic mater contents Soils of Intermediate Leaching Potential (I) This classification is applied to soils which have a moderate ability to attenuate diffuse source pollutants or in which it is possible that some non-absorbed diffuse source pollutants and liquid discharges could penetrate the soil layer. They include soils of the Evesham, Frilsham and Carstens Associations. Two sub- classes are recognised: I1: Soils which can possibly transmit a wide range of pollutants: and I2: Soils which can possibly transmit non- or weakly adsorbed pollutants and liquid discharges but are unlikely to transmit adsorbed pollutants Soils of Low Leaching Potential (L) This classification is applied to soils in which pollutants are unlikely to penetrate the soil layer because either water movement is largely horizontal, or they have the ability to attenuate diffuse pollutants. Lateral flow from these soils may contribute to groundwater recharge elsewhere in the catchment. They generally have a high clay content and include soils of the Wickham and Denchworth Associations. Copyright Environment Agency 14