A team led by Dr. Zhenghong Tang with the University of Nebraska ? Lincoln recently completed a 2-year project for the Great Plains Landscape Conservation Cooperative (GP LCC) designed to improve understanding of the status and function of playas in the Rainwater Basin of south central Nebraska. The project compared predicted location of playas based on hydric soil maps, the National Wetlands Inventory (NWI) and LiDAR-derived digital elevation models with actual inundated areas in the spring from 2004 to 2012. Although each method has limitations, all three confirm that landscape scale hydrologic changes associated with conversion of prairie to croplands have adversely affected playas. Results will allow GP LCC partners to identify and prioritize areas for playa conservation and restoration more effectively.

Playas are shallow depressions in the Great Plains that form seasonal wetlands. Millions of waterfowl depend on playas for resting and recharging energy stores depleted as they migrate. Playas also provide critical habitat for numerous resident species and serve an important role in recharge of aquifers. Unfortunately, many playas have been adversely affected by western settlement. Some playas have been eliminated directly, while others are affected by altered drainage patterns due to road and ditch construction and sedimentation from surrounding uplands converted from prairie to plowed cropland. The ongoing loss of playas is a major concern of GP LCC partners, including the Rainwater Basin Joint Venture (RWBJV). Much of the RWBJV's effort is focused on conserving remaining playas and restoring the function of playas affected by development. To increase efficiency, the RWBJV needs to know where playas are ? or were ? and how well they are currently functioning.

Two historic data sets have been used to predict where playas may occur. These are the Soils Survey Geographic dataset, which maps hydric soils, and the NWI. More recently, Light Detection and Radar (LiDAR) technology has been used to make more accurate topographic maps in the Great Plains where differences of only a few inches are hydrologically significant. The GP LCC identified the need to assess the accuracy of these tools to predict the location and functionality of playas to improve the efficiency of conservation and restoration efforts in the Great Plains.

Dr. Tang's team compared actual spring inundation areas based on Annual Habitat Survey data collected in the Rainwater Basin of south-central Nebraska between 2004 and 2012 with the three datasets used to predict seasonal wetlands. Although a high percentage of actually inundated areas fell within predicted locations based on each method, each had limitations. For example, the soil survey database grossly overestimated wetlands. Only 13 percent of the hydric soil areas were actually inundated, reflecting the fact that many of these areas no longer function effectively as playas. Conversely, the NWI underestimated inundation due to missing many smaller wetlands. The NWI also identified some man-made features as wetlands, even though these do not function as playas. Due to improved accuracy, LiDAR-derived maps were better aligned with actual inundation, but LiDAR misidentified some features, such as culverts or bridges, as dams which affected interpretation of drainage patterns. Dr. Tang's team developed ways of addressing this problem with the LiDAR-derived maps by incorporating data on the location of culverts and bridges into the analysis. In spite of the limitations associated with these methods, all three reveal that landscape level changes in hydrology have greatly reduced the number and functionality of playas.

Andy Bishop, coordinator of the Rainwater Basin Joint Venture said, "Understanding contemporary playa distribution and function is a major step forward for the RWBJV. We have already begun using this dataset to prioritize marketing and outreach to private landowners with functioning playa wetlands. This is important since this region is 99 percent privately owned and we have limited conservation delivery capacity. Landowners with these functioning playas routinely experience crop loss and diminished profitability therefore providing economical alternatives for these acres can result in a "win-win" where net farm income is increased and reliable playa wetland habitat maintained."

Results of this project are available on the GP LCC website. (cs)