Using GRACE satellite observations for separating meteorological variability from anthropogenic impacts on water...

Area of Science:

• Hydrology
• Climate Science
• Remote Sensing

Background:

• Total Water Storage Anomaly (TWSA) from GRACE is crucial for drought monitoring.
• The widely used Total Water Storage Deficit Index (TWSDI) can be inconsistent with meteorological data due to trends from human water use.

Purpose of the Study:

• To develop a modified TWSDI (MTWSDI) that distinguishes between anthropogenic and climate-driven components of TWSA.
• To introduce a deficit-based method for assessing drought severity and recovery time using GRACE data.

Main Methods:

• Decomposition of GRACE TWSA into anthropogenic and climatic components.
• Application of MTWSDI and deficit-based methods in the Ganges-Brahmaputra and Markazi basins.
• Comparison of MTWSDI with meteorological drought indices.

Main Results:

• MTWSDI showed improved consistency with meteorological drought indices in both study basins.
• The deficit-based method quantified annual water deficits, revealing significant anthropogenic contributions.
• Anthropogenic water deficits were equivalent to moderate to abnormally dry conditions annually in the studied basins.

Conclusions:

• MTWSDI offers a more reliable approach to drought monitoring by accounting for human water use impacts.
• Unsustainable water use is creating perpetual, accelerated anthropogenic droughts in the studied regions.
• Addressing these trends is critical to prevent basin depletion and socio-economic challenges.