Tuesday, June 18, 2019

Great Lakes near or at record high levels; scientists say climate change driving extreme swings in water levels

A pier on Lake Ontario is partially inundated by rising water and wind-driven waves. (Buffalo News photo)
Water levels in the Great Lakes have been high since 2014 and these days are at or near record highs. "In May, new high water level records were set on Lakes Erie and Superior, and there has been widespread flooding across Lake Ontario for the second time in three years. These events coincide with persistent precipitation and severe flooding across much of central North America, Drew Gronewold and Richard Rood write on The Conversation. Gronewold and Rood are professors at the University of Michigan who specialize in hydrology and climate science.

What happens to the Great Lakes matters; they contain about one-fifth of the world's surface fresh water, and more than 30 million people live in the Great Lakes basin, many of whom rely on the lakes for drinking water, industrial use, shipping and recreation, Gronewold and Rood report.

High water levels pose several problems for those who live near or depend on the Great Lakes, "including shoreline erosion, property damage, displacement of families and delays in planting spring crops. New York Gov. Andrew Cuomo recently declared a state of emergency in response to the flooding around Lake Ontario while calling for better planning decisions in light of climate change," Gronewold and Rood report.

Based on their research, Gronewold and Rood say climate change is causing rapid fluctuations between too-high and too-low water levels in the Great Lakes, and that this will be the new normal. Water levels in most Great Lakes were very low as recently as 2013, but began surging in 2014 after the "polar vortex" froze much of the lakes and caused evaporation to drop, even as regional precipitation began increasing.

Water levels are influenced by three main factors: rain and snowfall over the lakes, evaporation, and runoff that enters the lakes from tributaries and rivers. Runoff is affected by rain over land, snow and soil moisture. Warmer weather increases evaporation, but also causes snow to melt and runoff to increase. That makes for bigger swings in water level, especially considering that spring is coming earlier these days. Gronewold and Rood call for government agencies and weather forecasters to develop new tools to assess how future climate conditions could affect the Great Lakes' water levels, since current tools aren't capturing the whole picture.

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