The water footprint measures a human demand on freshwater. It is a multi-dimensional indicator that shows water consumption by source and polluted volumes by type of pollution; all components of a total water footprint are specified geographically (in place) and temporally (in time).
Water use and water consumption may have various meanings in the world; however, in regards to water footprint, their definitions are as follows:
Water use is measured in terms of water volumes consumed (evaporated) and/or polluted per unit of time. Usually three types of water usage are distinguished:
- Consumptive use of rainwater stored in soils as soil moisture (green water).
- Consumptive use of water withdrawn from groundwater or surface water (blue water).
- Pollution of water (grey water).
Water consumption refers to loss of water from the available ground-surface water body in a catchment area, which happens when water evaporates, returns to another catchment area or the sea or is incorporated into a product.