Wetlands are distinct ecosystems that are flooded or saturated by water, either permanently or seasonally. They are transitional areas between permanently flooded deepwater environments and well-drained uplands, where the water table is usually at or near the surface of the soil all year or for varying periods of time during the year, including during the growing season. Wetlands have unique characteristics, and they are generally distinguished from other water bodies or landforms based on their water level and on the types of plants that live within them. Wetlands are characterized as having a water table that stands at or near the land surface for a long enough period each year to support aquatic plants. Wetlands may support both aquatic and terrestrial species, and the prolonged presence of water creates conditions that favor the growth of specially adapted plants (hydrophytes) and promote the development of characteristic wetland (hydric) soils. Wetlands are valuable ecosystems that act like giant sponges or reservoirs, absorb excess water during heavy rains, limit the effects of flooding, protect coastal areas from storm surges, and absorb excess nutrients, sediments, and other pollutants before they reach rivers, lakes, and other water bodies.