Extreme water level variability on the Great Lakes

The Great Lakes are the largest surface freshwater system on Earth and serve the diverse needs of 30 million people. Water levels across the Great Lakes were very high throughout 2019 and 2020, approaching or exceeding seasonal or all-time record-high water levels at various times throughout the year. Only six short years earlier, shoreline communities on the Upper Great Lakes had been adjusting to a fifteen-year period of very low water levels. While water level fluctuations are normal on the Great Lakes, these extreme shifts between record low and high water levels fit the pattern of what would be expected under a changing climate. Projections for the future are not simply that water levels in the Great Lakes will trend up or down, but rather that they will experience more frequent periods of very high or very low levels. Planning is difficult in this context, as shoreline communities struggle to adjust and adapt to uncertain future conditions. Emerging insights from adaptive management theory and practice suggest that building resilience―the ability to withstand a wide range of scenarios―into both human and ecological systems is an effective way to cope with environmental change characterized by future uncertainty. The International Joint Commission (IJC) has adopted such an adaptive management approach as a means of dealing with future uncertainty on the Great Lakes.

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