Calcasieu Lake is a brackish lake located in southwest Louisiana, United States, located mostly within Cameron Parish. The Lake, also known as Big Lake to the local population, is paralleled on its west shore by Louisiana Highway 27, and is located about 17 mi south of Lake Charles, Louisiana. The lake is the natural outlet of the Calcasieu River. Com…Calcasieu Lake is a brackish lake located in southwest Louisiana, United States, located mostly within Cameron Parish. The Lake, also known as Big Lake to the local population, is paralleled on its west shore by Louisiana Highway 27, and is located about 17 mi south of Lake Charles, Louisiana. The lake is the natural outlet of the Calcasieu River. Commercial traffic uses the Calcasieu Ship Channel that runs down the west side of lake Charles and on the southern end splits Lake Charles from West Cove and exits the lake passing St Johns Island.