Global water resources affected by human interventions and climate change

Area of Science:

• Hydrology
• Climate Science
• Environmental Science

Background:

• The terrestrial water cycle is influenced by direct human activities, including dam construction and water withdrawals for various uses.
• Climate change is projected to further impact water supply and demand dynamics globally.

Purpose of the Study:

• To analyze and compare the impacts of climate change and direct human interventions on the terrestrial water cycle.
• To evaluate these impacts across different global warming levels, aligning with climate change mitigation targets.

Main Methods:

• Utilized a multimodel approach involving seven global hydrological models.
• Forced models with multiple climate projections, both with and without accounting for human impacts (dams, water withdrawals).
• Analyzed model results for various global warming levels (e.g., +2 K).

Main Results:

• Direct human impacts on the water cycle in regions like Asia and the western United States are comparable to or greater than impacts from moderate global warming (+2 K).
• Irrigation water consumption is projected to increase with rising global mean temperatures.
• Significant irrigation water scarcity is evident in parts of southern and eastern Asia, with projections indicating worsening conditions.

Conclusions:

• Human interventions significantly shape regional water cycle dynamics, often rivaling or surpassing climate change impacts at moderate warming levels.
• Future climate change is expected to exacerbate existing irrigation water scarcity, particularly in vulnerable regions of Asia.