The water level in Lake Superior has been slipping for years, and is now nearing record lows, according to the National Oceanic and Atmospheric Administration. Monitors put the current lake level at 183.028 meters, close to the record low for August of 182.97 meters.

The all-time record low water measurement for Superior - the largest of the Great Lakes - is 182.69 meters, set in April 1926. The record low water for September and October is 183.06 meters, NOAA says, so there is some possibility a new record low could be set this fall.

There are a variety of possible explanations for the falling water levels. The region has been experiencing unusually warm winters in recent years. Higher temperatures and reduced ice cover in winter causes greater rates of evaporation from the lake. And reduced snow cover has meant less runoff into the lake.

Some observers are also blaming years of drought and human factors, including water diversion and dredging, which has increased drainage from the lake. 

The drop in water levels has reduced shipping on the lake as carriers try to lighten their loads to avoid running aground. Marinas are also having to dredge or close as lake levels fall.

You can read more about it here.