Contribution of Anthropogenic and Climatic drivers to the Surface Water Extent Change in the Contiguous United States

Demographic expansion along with shifts in precipitation trends and temperature rise considerably impact the availability of surface water resources, causing serious consequences for human and the environment. The identification of the human and climatic dynamics contributing to the expansion and reduction of the extent of surface water bodies is key to guarantee the preservation of freshwater ecosystems and water scarcity.

In this work, we evaluated the variation of surface water extent and five potential drivers that occurred between 1984 and 2020 within the river basins of the contiguous United States (CONUS). We selected built-up area, population, and irrigated land as anthropogenic drivers, while precipitation and temperature represent the hydroclimatic drivers. The analysis of the interaction between changes in surface water extent and its drivers revealed that there has been an expansion of surface water extent over the majority of the CONUS, which was mainly induced by an increase in the mean annual precipitation, mostly in river basins with a continental and temperate climate. The reduction of the extent of surface water observed in the river basins in the arid southwestern region of the CONUS resulted to be influenced by all the anthropogenic and hydroclimatic factors, especially by temperature rise and population growth. We also noticed that river basins sharing the same climatic condition present similar trends of change in surface water extent and its drivers. In particular, arid river basins show distinct pattern of variations with respect to other climatic regions of the CONUS. This result highlights the need to further analyze these vulnerable areas where water availability is greatly affected on anthropogenic activities and climate change.