Environmental and community groups have sued Utah officials over failures to save its iconic Great Salt Lake from irreversible collapse.

The largest saltwater lake in the western hemisphere has been steadily shrinking, as more and more water has been diverted away from the lake to irrigate farmland, feed industry and water lawns. A megadrought across the US south-west, accelerated by global heating, has hastened the lake’s demise.

Unless dire action is taken, the lake could decline beyond recognition within five years, a report published early this year warned, exposing a dusty lakebed laced with arsenic, mercury, lead and other toxic substances. The resulting toxic dustbowl would be “one of the worst environmental disasters in modern US history”, the ecologist Ben Abbott of Brigham Young University told the Guardian earlier this year.