(Newser) – Two of the Great Lakes have hit their lowest water levels ever recorded, the US Army Corps of Engineers said today, capping more than a decade of below-normal rain and snowfall and higher temperatures that boost evaporation. Measurements taken last month show Lake Huron and Lake Michigan have reached their lowest ebb since record-keeping began in 1918. The lakes were 29 inches below their long-term average and had declined 17 inches since January 2012.

The other Great Lakes—Superior, Erie and Ontario—were also well below average. "We're in an extreme situation," says a corps official. The low water has caused heavy economic losses by forcing cargo ships to carry lighter loads, leaving boat docks high and dry, and damaging fish-spawning areas. The corps might reconsider a long-debated proposal to place structures in a river to reduce the flow of water away from lakes Huron and Michigan, which are connected.