Pan-European Vulnerability to Pollution: R-Layer - Net recharge

The R layer represents the mean annual net groundwater recharge for the climatic normal period 1961 - 1990, scored (classified) for index values 1...10 according to class breaks proposed by the HOVER project. The recharge caluclation was performed on an averaged montly basis using WORLDCLIM 1.4 climate data (precipitation, temperature, downscaled to 1 km resolution, https://www.worldclim.org/data/v1.4/worldclim14.html) and a temperature-based approach to claculate effective precipitation on a monthly basis after Samani and Hargreaves (1985). Annual diffuse net groundwater recharge was then estimated from effective precipitation using several environmental attenuation factors, as deduced from a scheme by Döll & Flörke (2005). Areas delineated by IHME1500 as "no groundwater" are blanked.