Changes in Major Global River Discharges Directed into the Ocean.

Area of Science:

• Hydrology
• Climate Science
• Environmental Science

Background:

• Global climate change is altering river discharge patterns worldwide.
• Understanding these changes is crucial for water resource management and ecological health.

Purpose of the Study:

• To analyze trends and identify causes of discharge variation in 40 major global rivers from 1960-2010.
• To quantitatively distinguish the contributions of climate factors and human activities to river discharge changes.

Main Methods:

• Developed a runoff variation attribution analysis method based on the Budyko hypothesis for large-scale basins.
• Incorporated human activities and glacial melting into the attribution model.
• Calculated contribution rates using elastic coefficients derived from factor and runoff change rates.

Main Results:

• Most rivers exhibited downward discharge trends, with notable regional variations (e.g., North America/Africa downward, Europe upward).
• Climate was identified as the primary driver of discharge changes.
• Human activities significantly impacted approximately 25% of river discharges.
• Upward trends were prevalent in subtropical monsoon humid and savanna climate zones (75% of basins), while tropical rainforest/monsoon zones showed downward trends.

Conclusions:

• Climate change is the dominant factor influencing global river discharge trends.
• Human activities play a significant role in specific regions, particularly in mid-low latitudinal zones.
• Discharge trends vary considerably with climate zones and latitude, necessitating region-specific management strategies.