Minnesota's original tallgrass prairie acted like a big sponge across a rolling landscape of prairie potholes, soaking up snowmelt and rain through deep-rooted grasses, burrowing animals, and fertile soil that stored water reserves for plants through summer heat and drought. When soils became saturated, water filled the potholes, then many dried as the season advanced, while the prairie continued to flourish. Unlike farm fields and urban lawns, where drainage systems and paving channel runoff quickly downstream and increase flooding and erosion, prairie landscapes allow precipitation to penetrate the soil, irrigate plants, and replenish groundwater. Landowners have applied lessons from the prairie by planting filter strips, buffer strips, and shallow vegetated swales to slow runoff, increase infiltration, and lessen erosion. Tallgrass prairie, named for grasses that can reach six feet by late summer, supports much of its life below ground, changes through the seasons, and benefits from fire, which helps maintain diversity and create space for new growth. Its deep roots control erosion, filter water, resist non-native plants, enrich topsoil, and help plants withstand drought. Once stretching from Saskatchewan to Mexico and from east of the Mississippi River west to the Central Great Plains, tallgrass prairie covered one-third of Minnesota before European settlement, but today only one percent of the state's original prairie remains. By 1980, 75 percent of Minnesota's prairie wetlands had been drained, intensifying the annual dry season. The Blanding's turtle, a state-listed threatened species of riparian areas and wetlands, nests in sandy upland soils, lays one clutch of 10 to 26 eggs a year, has a shell averaging 5.9 to 9.8 inches long, and is identified by a bright yellow chin and throat and a helmet-shaped shell; it is a shy but important member of the tallgrass prairie community and an indicator of aquatic ecological health.