Recent water level changes across Earth's largest lake system and implications for future variability

Water levels on Lake Ontario, the most downstream of the Laurentian Great Lakes, reached a record high in the spring of 2017. This event was accompanied by widespread flooding and displacement of families. Water levels across all of the Great Lakes have risen over the past several years following a period of record low levels. When levels were low, public and expert discussion focused on the possibility that low levels would continue into the future due to climate change, diversions of water from the lakes, and dredging. During the current high water period, variability is being attributed to water management, despite evidence of unusually high precipitation and river flows across the region. Understanding and communicating the drivers behind water level variability, particularly in light of recent extremes, is a fundamental step towards improving regional water resources management and policy.