LANDSAT ANALYSIS OF TEMPORAL AND SPATIAL CHANGES IN PRAIRIE POTHOLE LAKES OF NORTH AND SOUTH DAKOTA

The Prairie Pothole Region of North and South Dakota contains thousands of seasonal, semi-permanent, or permanent lakes that typically range in size from 0.1 to 10 hectares. These unique prairie wetlands are a phenomenon of an ubiquitous glacial terrain and continental climatic conditions dominated by short, hot summers and long, cold winters where potential evaporation greatly exceeds precipitation. This notoriously extreme climate produces periods of severe drought and deluge. During the last decade of the twentieth century, a period of deluge has considerably expanded the areal extent of prairie pothole lakes in North and South Dakota. A series of Landsat 5 and 7 images from 1990 and 2003, respectively, were selected and processed to assess the temporal and spatial changes in the pothole lakes. Accuracy of the changes was calibrated by comparing Landsat results to the changes observed on Digital Orthophoto Quadrangles for corresponding years. Error in estimated area was typically 10 percent or less for lakes greater than 1 hectare in size. A statistical analysis of the size of the pothole lakes was performed to determine distribution and changes. Results showed that about 50 percent of the lakes were within 0.5 hectares in size; and as lake size expanded, the average area increased from 3.6 hectares to 7.2 hectares. An evaluation of Digital Elevation Models indicated that most of the prairie pothole lakes which experienced size changes (those on the order of several hundred square meters in area) were concentrated at lower elevations.