Expected water levels on the Great Lakes for Jul 31, 2020.
Connecting Channels and the St. Lawrence River, given in inches above (+) or below (-) Low Water Datum (LWD). LWD is a plane of reference used on a navigation chart. It is also known as chart datum.
Great Lakes: Lake Ontario +39 Lake Erie +60, Lake St. Clair +62, Lake Michigan-Huron +56, Lake Superior +23.
St Lawrence River: Above Long Sault Dam +20, Above Iroquois Dam +26, Ogdensburg +32, Alexandria Bay +37. Head of River at Cape Vincent +39.
Detroit River: Lake Erie at Pelee Passage +60 Mouth of River at Gibraltar +65, Fort Wayne +66. Head of River above Belle Isle +62.
St. Clair River: Mouth of River at St. Clair Flats +62, Algonac +65, St. Clair +62, Blue Water Bridge +62, Head of River at Fort Gratiot +58, Lake Huron Approach Channel +56.
St. Marys River: Mouth of River at Detour +55, West and Middle Neebish +51, Head of Little Rapids +50, U.S. Slip +48, Above Locks +27, Head of River at Point Iroquois +23.
Available water depth is determined for a location by adding (if +) or subtracting (if -) the amount from the above to the water depth shown on National Oceanic and Atmospheric Administration (NOAA) navigational charts. Caution: Depths so determined are representative of a still water surface elevation, disturbed by neither wind nor other causes. Depth, however, may be reduced or increased as much as several feet for short periods of time due to these disturbances, or when sections of channels develop shoals. Vessel masters should refer to the Local Notice to Mariners for extent of shoaling and scattered bedrock projections in all channels. For further information direct inquires to: Department of the Army, Detroit District Corps of Engineers P. O. Box 1027, Detroit, MI 48231, (313) 226-6443. Additional information can be found on the U.S. Army Corps of Engineers Information Center website at