High-resolution mapping of global surface water and its long-term changes

Area of Science:

• Earth Observation Science
• Hydrology
• Climate Science

Background:

• Surface water dynamics are crucial for climate regulation, biodiversity, and human well-being.
• Previous global assessments of surface water changes lacked high-resolution, long-term data.
• Quantifying high-resolution, long-term changes in global surface water remains a significant challenge.

Observation:

• Utilized three million Landsat satellite images to map global surface water changes over 32 years (1984-2015) at 30-meter resolution.
• Recorded the seasonality and persistence of surface water, identifying areas of loss and gain.
• Documented changes in water occurrence, including seasonality and persistence, across diverse global regions.

Findings:

• A net global increase in permanent surface water was observed, with 184,000 sq km forming, contrasting with a loss of nearly 90,000 sq km.
• Significant water loss was concentrated in the Middle East and Central Asia (over 70%), linked to drought and human activities like damming and diversion.
• While reservoir filling contributed to water gain, climate change impacts on surface water occurrence were measurable globally.

Implications:

• The validated dataset provides crucial evidence of how climate change and human activities alter surface water distribution and persistence.
• This data can enhance climate modeling, wetland ecotone research, and inform critical water resource management decisions.
• Freely available data will support improved understanding of surface forcing and provide evidence for state and change in wetland ecosystems.