Mean Annual Groundwater Recharge of Germany 1:1,000,000 (GWN1000)

The map shows the average annual groundwater recharge of Germany for the period 1961 - 1990 as a raster image in a cell range of 1 x 1 km. For this purpose, a multi-step regression model was developed (Neumann, J. 2005). In a first step, the baseflow index (BFI = baseflow / total runoff) was determined as the regression target size as a function of slope gradient, drainage density, land cover, available field capacity, depth to groundwater and the ratio of direct runoff to total runoff. Based on this, two different model variants were developed for low-drainage (R < 200 mm/a) and high-drainage regions (R > 200 mm / a). For R < 200 mm/a, groundwater recharge rates were calculated by multiplying the regional grid-based baseflow index and the area-differentiated total runoff according to BAGLUVA. For the higher values R > 200 mm/a, a second regression equation has been used which, in addition to the base flow index, also requires the BAGLUVA total runoff and the depth to groundwater.