HISTORICAL SEDIMENT ACCUMULATION WITHIN HIGH PLAINS PLAYA WETLANDS AS A RESULT OF HUMAN MODIFICATION OF THE SHORT GRASS PRAIRIE

The High Plains of the central United States is underlain by thick, fertile soils, which has resulted in near total conversion of the prairie to cropland. Agricultural activities began in earnest during the late 1800s and peaked in the late 1920s and early 1930s. This, coupled with long-term drought, resulted in the Dust Bowl – one of the greatest environmental disasters in human history. Since then, a variety of soil conservation and landscape restoration techniques have been implemented. However, today little native grassland remains, and many watersheds are composed entirely of cropland.

We analyzed land cover trends and sediment accumulation for 20 playa wetlands on the High Plains of western Kansas. Playas were distributed among grassed playas with grassland dominated watersheds (GPGW), grassed playas with cropland dominated watersheds (GPCW), and cropped playas with cropland dominated water (CPCW). Land cover was confirmed using aerial imagery spanning 1991 to 2012. Sites were land surveyed and sediment depth was measured at several locations throughout playas by digging small pits and visually observing the sediment-soil boundary based on color and texture changes.

Results indicate that CPCW sites lost 13 – 48% (32% average) storage volume due to sediment accumulation, while GPCW sites lost 1 – 11% (5% average) and GPGW sites lost 2 – 9% (4% average). Converting native grassland to cropland can drastically reduce playa water storage volume, and, as a result, impair a host of other playa ecological functions. However, if grassland within and adjacent to playas is left intact, human impacts can be greatly reduced.