GSHP Screening Tool
Click on map to assess potential for open-loop (>100kWth) systems
Navigating the map
To pan: left-click on the map and drag.
To zoom: Drag the vertical slider on the left of the map, use the mouse wheel, hold down the Shift key and drag a rectangle, or use the 'Go to location' to enter a known location e.g. a place, postcode.
Initial screening layer
The application opens displaying the initial screening layer. The initial screening layer highlights all areas (light blue) where there is potential for the operation of open-loop GSHP systems (>100kWth). In these areas, a productive aquifer (> 1 L/s) is present within 300 m below the topographic surface.
Query initial screening layer
Click anywhere on the initial screening layer to show details of GSHP data layers at that point. The information presented is described in more detail below. A number of the results provide a 'Map' button which opens a sub map containing the data layer. A blue circle is displayed on the sub map showing the location queried on the initial screening layer. The sub map can also be queried by clicking anywhere on the map.
Bedrock aquifer layer
The bedrock aquifer layer shows where an aquifer is present at the surface (“at outcrop”) and/or “concealed at depth” (i.e., the aquifer lies under less permeable rocks). Each category includes a yield range which refers to the maximum yield that can be obtained from a single borehole. Concealed aquifers were mapped for the main geological formations that form important aquifers at depth and can provide yields of at least 1 L/s.
Depth to source layer
This layer estimates the depth (below the ground) to the water source. This is typically the depth to the water table or to the top of the water bearing strata (=aquifer) where it is covered by superficial deposits or by less permeable bedrock (i.e., concealed aquifer). The layer is included here to give an indication of the minimum depth of drilling that is required for borehole installation. It refers to the uppermost aquifer where more than one is present.
Protected areas layer
The layer outlines where protected areas, including Source Protection Zones (SPZ), Sites of Special Scientific Interest (SSSIs) and/or National Parks are present. In these areas additional protection is required to safeguard drinking water supplies, wildlife and habitats or special landscape qualities through restricting activities that may affect any of these features. These are included here to show where restrictions on water abstraction/reinjectionmay apply. For further details see: http://www.environment-agency.gov.uk/homeandleisure/37833.aspx,https://www.ccwater.org.uk and http://publications.naturalengland.org.uk.
Existing licensed abstractions layer
This field shows what abstraction volumes have been licensed by the Environment Agency within a radius of 600m around the search location. The values refer to the total daily abstraction allowance per site/licence and can represent the combined yield from multiple boreholes. Where two or more values are found, these may refer to different aquifers and depths. The information is included here to show what daily yields can be achieved in the area of interest. It is not indicative of the licence that can be agreed with the Environment Agency as this will depend on the availability of water in the area. Details on this can be found at the Environment Agency’s website at https://www.gov.uk/government/collections/water-abstraction-licensing-strategies-cams-process .
Groundwater chemistry layer
Groundwater chemistry data are provided for all groundwater sampling points within 600m radius of the search location. Where two or more values are found, these may refer to different aquifers, depths or times of sampling. These data are included here to give an indication of the groundwater chemistry that can be expected around the area of interest. Please note that these data are only available for about 2% of the mapped area.
A set of empirical indices is provided that estimate (1) the tendency of the water (at in-situ temperature) to form/dissolve calcium carbonate scale (Langelier Saturation Index, Ryznar Stability Index) and (2) the corrosiveness of the groundwater towards steel (Larson-Skold Corrosive Index) (Table 1). It is also shown if iron concentrations in the groundwater are beneath or above the threshold value of 500µg/L . Concentrations equal to or greater than this threshold value may cause problems for open loop GSHPs due to precipitation and clogging of the pump or wells.
LSI > 0.4
RSI < 6
Calcium carbonate precipitation
LSCI < 0.8
0.4 > LSI > -0.4
6 < RSI < 7
0.8 < LSCI < 1.2
LSI < -0.4
RSI > 7
Calcium carbonate dissolution, =scaling unlikely
LSCI > 1.2
Table 1: Interpretation of scaling/corrosion indices
Note: Some experts prefer LSI > 1.5 (up to 2.5) as the break point for scale formation and LSI < -1.5 as indication of aggressive water. Likewise, some experts consider only waters at RSI <4.5 as definitely scale forming and waters at RSI > 8.5 as clearly aggressive.
Limitations of the tool
For further information see:
Technical Guide - A screening tool for open-loop ground source heat pump schemes (England and Wales): http://www.bgs.ac.uk/downloads/start.cfm?id=2648
Non-technical Guide - A screening tool for open-loop ground source heat pump schemes (England and Wales): http://www.bgs.ac.uk/downloads/start.cfm?id=2646