A Lacustrine System is - according to the USDA terminology - "composed of wetlands and deepwater habitats occurring in one of five systems in the classification of wetlands and deepwater habitats . The Lacustrine System includes wetlands and deepwater habitats with all of the following characteristics:
- situated in a topographic depression or a dammed river channel;
- lacking trees, shrubs, persistent emergent plants, emergent mosses or lichens with greater than 30% areal coverage; and
- total area exceeding 20 acres. Similar habitats totaling less than 20 acres are included if an active wave-formed or bedrock shoreline feature makes up all or part of the boundary, or if the water depth in the deepest part of the basin exceeds 6.6 feet at low water."