Table 1
Calculation of WSF indices.
Land use category Calculation of WSF index
Glaciers and snowfields Average water runoff per year of the land surface
areas covered by glaciers and snowfields
multiplied by availability factors
Forests, pastures, arable
land, residential areas
Average rainfall minus evapotranspiration of the
land surface areas covered by the respective land
use pattern multiplied by availability factors
Industrial areas Average rainfall minus evaporation on sealed
areas except traffic areas (roofs, storage areas)
multiplied by availability factors
Streets and parking lots Average rainfall minus evaporation on sealed
public and private traffic areas multiplied by
availability factors
Desalinated water WSF of virtual water needed to produce the
energy (water needed as cooling agent in caloric or
nuclear power plants) required for the
desalination plant
Recycled water WSF index is zero if water does not have to be
purified and no virtual water is needed in the
purification process
Virtual water As virtual water has to be supplied within the
catchment area the WSF is calculated from
average regional rainfall minus average regional
evapotranspiration multiplied by availability
factors