• the smallest by volume
• the shallowest
  • warms rapidly in the spring and summer
  • frequently freezes over in winter
  • average depth is only about 62 ft. (19m)
  • the western basin (about 20% of the lake), is very shallow with an average depth of 24 ft. (7.4m) 
• retention time = 2.6 years (a measure based on the volume of water in the lake and the mean rate of outflow)
• most of the land area around the lake is urban or agricultural
• 17 metropolitan areas with populations over 50,000 within the Lake Erie basin
• significant effects from urban and agricultural runoff

from Lake Erie Binational Nutrient Management Strategy, 2011

The Lake Erie watershed, the most populated of all Great Lakes basins, is very diverse. It is largely agricultural, intensively industrialized, and highly urbanized. About one third of the total population of the Great Lakes basin resides within the Lake Erie watershed. This amounts to 11.6 million people (10 million U.S. and 1.6 million Canadian), including 17 metropolitan areas, each with more than 50,000 residents. Lake Erie provides important natural, economic and recreational values and provides drinking water to 11 million people.

Of all the Great Lakes, Lake Erie is exposed to the greatest stress from urbanization, industrialization and agriculture. Lake Erie surpasses all the other Great Lakes in the amount of effluent received from sewage treatment plants and is also most subjected to sediment loading due to the nature of the underlying geology and land use. Exposed agricultural and urban lands, particularly in southwest Ontario and northwest
Ohio, contribute immense sediment loads to the lake.

Lake Erie is the smallest of the Great Lakes by volume and also the shallowest. It warms quickly in the spring and summer and cools quickly in the fall. The shallowness of the basin and the warmer temperatures make it the most biologically productive of the Great Lakes.

• Eighty percent of Lake Erie’s total inflow of water comes through the Detroit River
• Eleven percent is from precipitation (rain and snow)
• The remaining nine percent comes from the other tributaries

Bathymetry of Lake Erie and Lake St. Clair

• The western basin is very shallow, with an average depth of 7.4 metres (24 ft) and a maximum depth of 19 metres (62 ft). It is the most turbid region of the lake as most of the lake bottom is covered with fine sediment particles that are easily disturbed by wind and wave action.
• The central basin is quite uniform in depth, with an average depth of 18.3 metres (60 ft) and a maximum depth of 25 metres (82 ft).
• The eastern basin is the deepest of the three basins, with an average depth of 24 metres (80 ft) and a maximum depth of 64 metres (210 ft).

The central and eastern basins thermally stratify every year.

Stratification refers to the layering that occurs, particularly in the warmer months, where a warmer, less dense layer of water (the epilimnion) overlies a colder denser layer (the hypolimnion). Stratification can occur in the western basin but does not last very long. Stratification impacts the internal dynamics of the lake physically, biologically and chemically, and this in turn affects the amount of dissolved oxygen present at the bottom of the lake.

Lake Erie & St. Clair Maps from National Oceanic and Atmospheric Administration