Satellite imagery published by NASA on Saturday reveals the extent of flooding caused by the Lower Sesan II hydropower dam, and the change in the landscape in just one year.

“The Operational Land Imagery (OLI) on the Landsat 8 satellite captured these before and after natural-color images of the dam and reservoir,” NASA, the US National Aeronautics and Space Administration, wrote in a news release posted to the Earth Observatory website, the agency’s public outreach arm.

One image from February 14, 2017, shows the dam still under construction, with the Sesan and Srepok rivers still flowing freely, while an image from February 1 this year shows the after-effects of the closure of the dam’s floodgates in September, creating a 75-square kilometer reservoir.

Annotated Landsat 8 satellite imagery dated February 14, 2017. Photo courtesy of The Earth Observatory/NASA

“The brown and light green areas in the first image, particularly those with straight edges, were likely cleared recently for timber; some of the smaller tan areas were crop fields near villages. Densely forested areas are green,” NASA wrote.

Annotated Landsat 8 satellite imagery dated February 1, 2018. Photo courtesy of The Earth Observatory/NASA

The controversial dam cost some $800 million, and has drawn criticism over the displacement of villagers living in the reservoir area, many of whom are ethnic minorities. Justified by the government as a necessary source of cheaper energy, environmental experts have pointed to how the changing global climate may soon make hydropower dams on the Mekong and its tributaries inefficient or obsolete as water flows become unpredictable. A 2012 study published in the Proceedings of the National Academy of Sciences projected the Lower Sesan II dam would reduce the productivity of the Mekong Basin fisheries by nearly 9 percent.

Read more: Life after the flood: Sesan dam holdouts rue their losses – but see a fragile victory