According to the 2000 census , the county has a total area of 672.20 square miles ( 1,741.0 km2 ) , of which 614.15 square miles ( 1,590.6 km2 ) ( or 91.36 % ) is land and 58.05 square miles ( 150.3 km2 ) ( or 8.64 % ) is water ( including parts of the Detroit River and Lake St. Clair ) .
Of this , 614.15 square miles ( 1,590.6 km2 ) ( or 91.36 % ) is land and 58.05 square miles ( 150.3 km2 ) ( or 8.64 % ) is water Parts of the Detroit River and Lake St. Clair are included in the county .