Day County, located in the northeastern corner of South Dakota, sits within the Coteau des Prairies – a plateau created from deposits derived from repeated glaciation. Many small lakes occur in this region due to a perched water table. In the past 20 years, lake waters have been swallowing up land, roads, and homes in the region. The area around the town of Waubay, which is noted on these Landsat images acquired in 1991 and 2011, is particularly affected.
Bitter Lake, south of Waubay, is the southern boundary for the water flowing from Waubay, Blue Dog, and Rush Lakes from the north, and has no established outlet for the water to flow further south. As in many prairie pothole lakes, the main sources of water loss are evaporation and seepage into groundwater, instead of river drainage. During this regionally wet time, the groundwater levels rise, so evaporation is the only option for reduced lake levels. As Bitter Lake waters continue to rise, the entire area floods, consuming more land that was once farm fields, pasture ranges, and homesteads.
The 40-year archive of Landsat imagery is an effective resource for seeing the land change from space.