OutdoorNebraska

21 GUIDE TO NEBRASKA'S WETLANDS Playa Wetlands P laya wetlands are wind-formed depressions located in semi-arid areas. Many are nearly circular or oval, but others have more irregular boundaries. They have a clay layer in the soil under the wetland that when wet, ponds water on the surface and slows the movement of the water into the ground. This clay layer was formed by water movement over thousands of years. Most playas are not directly connected to groundwater. The major playa complexes in Nebraska include the Rainwater Basins, Central Table Playas, Southwest Playas, and the Todd Valley. RAINWATER BASIN Profi le The Rainwater Basin complex was named for the abundant natural wetlands that formed where clay- bottomed depressions catch and hold rain and runoff water. It covers a 6,150-square-mile area across all or parts of 21 counties in south-central Nebraska. The landscape of the complex is characterized by fl at to gently rolling plains formed by deep deposits of wind-blown silt-loam soil. The wetlands were formed by wind action and tend to have a northeast to southwest orientation. There frequently is a hill, or lunette, located immediately south or southeast of the wetland where the windblown loess was deposited. Natural surface water drainage in the region is poorly developed, resulting in numerous closed watersheds draining into these wetlands. Most of the wetlands in this region do not receive groundwater infl ow. Wetlands range in size from less than 1 to more than 1,000 acres. Loss and Threats Analysis of the historic soil surveys (1910-1917), National Wetland Inventory (1980-1982), and Soil Survey Geographic (SSURGO) data (1961-2004) indicated playa wetlands were once a prominent feature of this landscape. Combined, these datasets identifi ed approximately 11,000 individual playa wetlands comprising 204,000 acres that were historically part of the landscape (RWBJV 2013a). It has been estimated more than 1,000 semipermanent and seasonal wetlands covered over 70,000 acres, and more than 10,000 temporary wetlands accounted for an additional 134,000 acres. A Nebraska Game and Parks Commission breeding waterfowl habitat survey (McMurtrey et al. 1972) used the historic soil surveys as a reference to evaluate the distribution of remaining wetlands. McMurtrey et al. (1972) reported 82% of the major wetlands had been converted to agriculture, removing approximately 63% of the total wetland acres from the landscape. The fast- paced degradation continued, and by 1982, only 10% of the surveyed wetlands remained. The remaining wetlands represented only 22% of the original surveyed acres, and virtually all were hydrologically impaired (Schildman and Hurt 1984). This trend study did not attempt to estimate the quantity and quality of smaller wetlands that were not identifi ed on early soil surveys. However, because small wetlands are more vulnerable to destruction, it is likely that the proportion of loss documented by Schildman and Hurt for larger wetlands is even greater for the smaller wetlands. Using National Wetland Inventory digital data and contemporary soil survey maps, a multiagency wetland team in 1990 identifi ed 34,103 acres of Playa wetlands are wind-formed depressions that pond water over a clay layer in the soil. This Southwest Playa in Chase County is farmed in most years. ETHAN FREESE, PLATTE BASIN TIMELAPSE

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