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Water levels in the Great Lakes are rising from record lows. Lakes Huron and Michigan are 3 feet higher than a year ago. Here's NPR's David Schaper.
DAVID SCHAPER, BYLINE: Walking over the foredune towards the sparkling blue-green waters of Lake Michigan at Central Avenue Beach in the Indiana Dunes National Lakeshore, you'd expect to find a long, gradual, sandy descent to the water's edge. But instead...
MIKE BREMER: That sand's gone now. It's washed away.
SCHAPER: Chief ranger Mike Bremer says just a year ago, this beach was 50 feet wide. Now it's just a sandy cliff with a sharp 8- to 12-foot drop-off to the jagged remnants of an old, broken-up road below that had been buried under the sand.
BREMER: It's rock, concrete, asphalt, debris, the big clay blocks, other woody debris down there. There's a lot of things that people could get hurt on.
SCHAPER: So this beach is now closed because the rapidly rising water level of Lake Michigan allowed storm-driven waves to reach higher onto the beach and carry most of the sand away.
BREMER: When we got out here in the springtime, that 50 feet had been reduced down to more along the lines of about 15 to 20 feet. And then the storms we had a few weeks ago pretty much took the rest of that.
SCHAPER: This beach would eventually be replenished naturally with sand the lake would carry from other beaches to the east and north, but man-made structures, such as docks, piers and breakwaters, are holding back the sand that would normally flow to this beach. Some waterfront homes and other structures also could be threatened by the higher water levels in coastal erosion. But what's bad for the beaches and homes is good for recreational boaters and commercial shippers.
KEITH KOMPOLTOWICZ: In the Great Lakes, it's really kind of in the eye of the beholder.
SCHAPER: Keith Kompoltowicz is chief watershed hydrologist for the Detroit District of the U.S. Army Corps of Engineers. He says the lakes were in the midst of an unprecedented 15-year stretch of very low water levels, hitting a record low in January of 2013. Kompoltowicz says many harbors and marinas had to dredge in order to remain open while shipping companies had to lighten their loads to get freighters in and out of ports, all at great expense. And some wondered if the lower Great Lakes' water levels were becoming the new normal. But since the winter of 2013...
KOMPOLTOWICZ: And then it started to rain, and it really hasn't stopped raining for the past couple of years.
SCHAPER: Above-average rainfall, snowfall and increased runoff has been refilling the lakes while colder temperatures and icier winters reduce the amount of lake water lost to evaporation. Hydrologist Drew Gronewold at NOAA's Great Lakes Environmental Research Lab gives some of the credit to the dreaded polar vortexes.
DREW GRONEWOLD: The cold air masses that came over the Great Lakes in the past couple of winters are certainly related to this as is the subsequent formation of ice.
SCHAPER: Now Lakes Michigan and Huron, as well as Superior, which is also rising at a record rate, are still below their all-time high levels. The lakes are just about a foot above average right now. But what piques the interest of scientists such as Gronewold is such a rapid water-level rise right after the historic low.
GRONEWOLD: Right in the midst of this period where we have persistent below-average water levels and evaporation as a dominant process, we suddenly have a record-setting two-year surge. And I do find that to be a compelling juxtaposition.
SCHAPER: On Chicago's North Avenue Beach, rising waters have swamped some beach volleyball courts. But Joel Brammeier of the Alliance for the Great Lakes isn't so concerned just by the fact that the lake level is up.
JOEL BRAMMEIER: Natural fluctuations in the levels are actually good for the Great Lakes. They help to nurture the fish and wildlife that live there, and they're a sign of a healthy system.
SCHAPER: But Brammeier is concerned about how fast the water is rising and that such extreme fluctuations are becoming more common and more difficult to predict in any given year.
BRAMMEIER: That's probably a symptom of a changing global climate. We're seeing more extreme storms, less predictable temperatures on any given season, and that has an effect on these massive bodies of water.
SCHAPER: And since the Great Lakes contain more than one-fifth of the surface freshwater in the world, Brammeier and others want more study of the effects of climate change and stronger policies to protect the lakes for future generations. David Schaper, NPR News, Chicago. Transcript provided by NPR, Copyright NPR.