Straight from the Tap

Cooler Weather Will Reduce Lake Levels


As colder air masses move over a warm Lake Erie, people who frequent the coast should notice a change – decreasing lake levels.

Lake Erie's water level for August 1 started out at 574.47 feet and is ending the month around 574.15 feet.

These water levels are still several inches higher than they were this time last year and more than 2.5 feet higher than the August monthly average thanks to a record-breaking summer.

For the past 2 years, water levels have been much higher than average with an all-time record monthly average water level set in June of 574.61 feet. Even July’s monthly average of 574.57 feet topped the previous historic monthly high water level of 573.95 feet, set in July 1986.

The water level of Lake Erie constantly undergoes natural fluctuation, including daily changes, seasonal cycles, and long-term changes. These changes are closely monitored and recorded by various Cleveland Water partners including the National Oceanic and Atmospheric Administration (NOAA) and the U.S. Army Corps of Engineers (USACE).

NOAA maintains a database of water levels for each Great Lake that extends back more than 100 years while the USACE tracks daily levels and forecasts how water levels will change daily, weekly, and monthly. Both data sets are important economically to the shipping and boating industries and help the USACE plan dredging and harbor maintenance projects.

Lake levels change based on two variables: water input and water outflow. Water input is greatest in the spring and summer in response to winter snowmelt and spring rains and runoff. Water outflow in the form of evaporation is greatest when the temperature difference between the water and the air is greatest. This occurs in the early fall when the cold air masses move over the lake which still retains the heat from summer. Water temperatures, also tracked by NOAA, then drop as evaporation takes heat away from the lake. When evaporation is greatest, Lake Erie can lose several inches of water in a week.

While the water level changes on Lake Erie can be dramatic for those who live, work or play along the lakeshore, water level changes do not impact our ability to continue producing high quality, safe and great tasting water that is delivered to your tap.