Timing of Global Surface Water Transitions Reveals Anthropogenic Dominance of Recent Growth in Water Extent

Abstract

The extent of coastal and inland surface water resources is constantly varying in response to complex interrelated processes, driven by natural and anthropogenic factors. Recent advance in satellite technology and cloud computing have enabled global-scale monitoring of the changing occurrence and extent of these surface water resources. However, until now, no previous study has sought to estimate the timing of these surface water changes at the global-scale. Here we introduce the first global-scale identification of the year when water advanced or receded within a given pixel, using a 38-year Landsat time series. Our methods focus exclusively on persistent changes in water features, filtering out seasonal or short-lived fluctuations. We use the new algorithm to map the timing of water advance and/or recession events globally, encompassing both inland water bodies and coastal dynamics. Additionally, the timing of water transitions enabled the identification of the primary drivers behind these changes. As a result, we identified that most of the large-scale water change events are related to human influence, such as damming, infrastructure failures and even conflicts. These combined factors contributed to a global shift, with accumulated water advancing surpassing water receding over time.