Platte Lake is one of the many lakes located in the northwestern part of Michigan's lower peninsula. There are two lakes in Benzie County, Michigan based on the name Platte, the other being Little Platte. Platte Lake covers 2,516 acres and is 3.3 miles long and 1.6 miles wide. The average depth of Platte Lake is 24 feet deep. The deepest point of th…Platte Lake is one of the many lakes located in the northwestern part of Michigan's lower peninsula. There are two lakes in Benzie County, Michigan based on the name Platte, the other being Little Platte. Platte Lake covers 2,516 acres and is 3.3 miles long and 1.6 miles wide. The average depth of Platte Lake is 24 feet deep. The deepest point of the lake is measured at 95 feet deep. The Platte River flows through the lake at a speed of 120 cubic feet per second. This means the residence time for the water in Platte Lake is 6 months. Also meaning that every hour 3,300,000 US gallons of water are passing through Platte Lake. The Platte River flows through Platte Lake and continues downstream through Loon Lake until it finally reaches Lake Michigan.