Capping Human Water Footprints in the World's River Basins

Area of Science:

• Hydrology
• Environmental Science
• Water Resource Management

Background:

• Global water scarcity is exacerbated by increased demand and overexploitation of freshwater resources.
• This leads to economic instability and conflicts over water allocation worldwide.
• Establishing water footprint caps is a proposed policy to manage human water consumption within ecological boundaries.

Purpose of the Study:

• To estimate globally the monthly blue water flows available for human use in all river basins.
• To explicitly reserve water for environmental flow requirements.
• To analyze trade-offs between environmental flow requirements and water resource utilization, especially in basins with high variability.

Main Methods:

• Estimation of monthly blue water flows for human allocation across all global river basins.
• Quantification of trade-offs considering temporal variability in water availability.
• Analysis of seasonal and interannual variability impacts on water allocation.

Main Results:

• The study provides estimates of allocable blue water flows for human uses in river basins worldwide.
• Quantified trade-offs highlight the challenges in balancing environmental needs with human appropriation, particularly in variable basins.
• Identified limitations and challenges for the practical implementation of water footprint caps.

Conclusions:

• Local and time-specific water footprint caps are crucial for sustainable water management.
• Policy makers need to agree on specific capping procedures for effective implementation.
• Water footprint caps can be linked to the planetary boundary for freshwater use to ensure global sustainability.