The water footprint is a measure of the total volume of freshwater used directly or indirectly by a person, industry, or nation. It is divided into three types: blue, green, and grey water footprints. Each type represents a different aspect of water use and its environmental impact.
1. Blue Water Footprint
- Definition: Refers to the volume of surface water and groundwater consumed during production processes.
- Examples:
- Irrigation from rivers or borewells.
- Water used in industrial cooling or manufacturing.
- Source: Freshwater from lakes, rivers, reservoirs, or underground aquifers.
- Impact: Leads to depletion of water bodies and affects aquatic ecosystems if overused.
2. Green Water Footprint
- Definition: Refers to the amount of rainwater stored in soil and used by crops through evapotranspiration.
- Examples:
- Water used by crops grown under rain-fed conditions (like wheat, pulses).
- Source: Rainwater that does not run off but stays in the root zone.
- Impact: Less harmful to ecosystems; important in agriculture and food security.
3. Grey Water Footprint
- Definition: The volume of water needed to dilute pollutants in wastewater to meet environmental standards.
- Examples:
- Water required to dilute industrial effluents or domestic sewage.
- Source: Indirect – not water used, but water needed to clean the environment.
- Impact: Reflects pollution load, important for wastewater management.
Comparison Table
| Type of Water Footprint | Source of Water | Use Type | Environmental Concern |
|---|---|---|---|
| Blue | Surface & Groundwater | Irrigation, industrial use | Depletion of freshwater sources |
| Green | Rainwater (soil) | Crop growth (rain-fed farming) | Least impact, sustainable |
| Grey | Calculated Volume | Diluting pollutants in wastewater | Water pollution & quality concern |