Understanding the Asian water tower requires a redesigned precipitation observation strategy

Area of Science:

• Hydrology
• Climatology
• Environmental Science

Background:

• The Asian water tower (AWT) is crucial, supplying 10 major rivers and supporting 2 billion people.
• Reliable precipitation data is essential for understanding the AWT's water cycle.

Purpose of the Study:

• To quantitatively assess precipitation underestimation over the AWT.
• To identify causes of measurement errors and their impact on water cycle understanding.

Main Methods:

• Analysis of evapotranspiration, runoff, and accumulated snow data.
• Identification of instrumental and representativeness errors in precipitation measurements.

Main Results:

• Observed precipitation over the AWT is significantly underestimated.
• Paradoxical water balance components (evapotranspiration, runoff, snow) indicate underestimation.
• Wind-induced gauge undercatch and sparse-uneven gauge density are key error sources.

Conclusions:

• Current precipitation data for the AWT is unreliable.
• Previous water cycle studies in the region may require re-evaluation.
• Addressing measurement errors is critical for accurate AWT water resource management.