The proportion of water held in the soil at field capacity (5KPa) and at the permanent wilting point (1500kPa) was calculated for each soil horizon of each soil taxonomic unit (soil series) delineated within the 1:250 000 national soil map of Scotland based on pedotransfer functions (regression equations using median sand, silt, clay and organic carbon contents from the Scottish soils knowledge and information base (SSKIB) derived for soils in the UK (Hollis et al., 2015). The Available Water Content for each horizon was calculated by subtracting the water content at 1500 KPa from the water content at 5 kPa. The horizon thickness was then multiplied by the available water content (mm) and summed for the entire soil profile to 1 m or rock if <1m. The map shows the average available water capacity calculated using the areal proportions of all soils in each 1:250 000 soil map unit.
Gagkas, Z., Lilly, A., Baggaley, N. & Donnelly, D. (2019). Map of available water capacity of soils in Scotland. James Hutton Institute. Aberdeen.
Please note that this dataset differs significantly to the version of Available Water Capacity published in 2012. The difference results from the use of different regression equations to predict available water capacities (Hollis et al.) and bulk densities. In addition, the data values shown are weighted averages by polygon rather than the AWC of the dominant soil type in the polygon. The earlier version of AWC was published as Lilly, A, Baggaley, N and Donnelly, D. 2012. Map of available water content to 1 metre depth in soils of Scotland. Map prepared for EU project GS-SOIL-Assessment and strategic development of INSPIRE compliant Geodata-Services for European Soil Data. ECP-2008-GEO-318004.
