PLAYAS IN COLORADO. 17 December 2010 Page 1

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1 PLAYAS IN COLORADO Background and Identification of Interaction with Wind Development 1 Playas are round, shallow, clay-lined wetlands found throughout the short- and mixed-grass prairie region. It is estimated that approximately 100,000 playas exist in the Great Plains region. Within Colorado, playas are located on the eastern plains with recent desktop estimates indicating approximately 7,200 potential playas. 2 Precipitation and associated runoff is the sole source of water for playas. 3 A study in Texas found that, on average, in January a playa has water in 1 out of 3 years. 4 Playas are not easily identified, often not captured by traditional wetland mapping methods and have an unpredictable hydroperiod. For example, in Nebraska, National Wetlands Inventory (NWI) maps identify playas with 91% accuracy 5, but in Colorado accuracy varies from 33 to 54% 6. Because of the high level of uncertainty around playas in Colorado, field verification is an important part of documentation. Once a playa is identified, whether a playa has water, how much water is in it from year to year, and how long that water will be retained is unpredictable. Placing wind turbines and transmission lines in and among playa complexes may increase the risk of collision mortality for waterfowl and other wetland dependent birds. Wet playas attract large numbers of wetland dependent birds and those that prey on them. Waterfowl (e.g. ducks and geese), shorebirds (e.g. plovers, rails, sandpipers) and waterbirds (e.g. cranes), as well as the birds that prey on them (e.g. raptors), use inundated playas during migration as stopover points for feeding and resting. Proximity of wind turbines to playas may affect avian mortality as birds traverse among playas. Wind development and associated infrastructure on or near playas may adversely affect wildlife habitat. 7 In some areas, where playas are the only source of nearby surface water, they can attract many species of wildlife, often in high concentrations. 3 Wet playas are known to be habitat for amphibians, a taxon which is experiencing world-wide declines, 5,6 and reptiles such as the yellow mud turtle. 3 Bats are known to feed on emerging insects at wet playas. 3 Placement of wind turbines in playas may reduce water-holding capacity and reduce or degrade habitat for wetland dependent species. Development of wind farms on playa wetlands (either directly within a playa or among a complex of playas 8 ) may limit the normal function of the playas. Playas recharge the High Plains Aquifer (Ogallala) by allowing percolation of surface water through the clay layer of soil in the basin. 9 Recharge through playa basins occurs at a rate 1 to 2 orders of magnitude greater than through inter-playa areas. 9 Damaging the clay layer 10 is documented to inhibit this recharge function and increase the influx of polluted water to the aquifer. State of the Science The number of documented playas is approximately 60,000 although some estimates range toward 100,000 playas. 1 Where studies are completed, high quality maps of the locations of playas are available. In Colorado, Rocky Mountain Bird Observatory and Playa Lakes Joint Venture can provide GIS data for the location of known playas at the state and county level as illustrated by the summary information provided in Table1 and Figure 1. Because of highly variable hydroperiods associated with each playa, bird and amphibian use is also highly variable from playa to playa. However, research in eastern Colorado has shown that larger playas in complexes displayed higher use by waterbirds and shorebirds than smaller, isolated playas for some species groups. 11 There is risk of declaring playa basins to be unused by birds or amphibians because of the long-term ephemeral nature of playa hydroperiod. For example, playas may be dry for many years and then fill with water during a rain event and subsequently host many bird and other wildlife species. There is a paucity of data regarding the risk of avian/turbine collisions in the vicinity of playas. Current conclusions in this BMP are based on the data from more thoroughly-studied birds that use playas, such as cranes, and that have a high collision risk with tall structures. Placing wind turbines in playas may negatively impact playa aquifer recharge and playa biodiversity function. Scientific studies have documented the recharge to the Ogallala aquifer through playas and the negative impacts of puncturing the clay layer in the playa basin. Modified playa basins lose their hydroperiod and cease to function properly, which could affect birds, amphibians, and other wildlife through habitat loss. 17 December 2010 Page 1

2 Best Management Practices Conduct surveys for playas in areas where playas are known to or may exist (see Table 1 and Figure 1). Detailed locations of documented playas can also be found by using the GIS data available from the Playa Lakes Joint Venture ( Note that as with any remotely gathered data, some playas are missed in the GIS mapping while other sites mapped as a possible playa may not be. Confirmation is best done on site using soils data and other playa characteristics (e.g. hydrology, soils, and plants). Wind developers should work with experts knowledgeable about playas to determine playa locations and appropriate conservation measures. Avoid Development of wind farms within confirmed playas or playa complexes should be avoided because of the important biodiversity and recharge functions of playas. Due to the seasonality of playas and the potential for large numbers of birds to use the playas when wet, playas should be avoided to reduce the risk of fatality events. Placing infrastructure within the playa floor can have a negative impact on habitat and hydrology. The playa basin is defined as the area of a playa that contains or potentially contains water, as confirmed by site surveys. Minimize If placement of wind farm infrastructure on a playa or complex of playas is unavoidable, then the following recommendations to reduce the likelihood of collision-related mortalities and impacts to the playa hydrologic cycles should be considered. Below are a number of possible minimization efforts. 1. The Federal Advisory Committee Draft Recommendations for wind energy development discuss avoidance of daily movements of bird and bat species: Locate turbines to avoid separating bird and bat species of concern from their daily roosting, feeding, or nesting sites if documented that the turbines presence poses a risk to species. (Chapter 3, page 45; Draft Recommendations 3/2010) 12 Pre-construction studies may reveal regularly used flight paths (i.e. to roosts, feeding areas, other playas, etc.). Avoidance of these flight paths (e.g. ingress and egress corridors, between playas and food sources such as agricultural fields) may decrease collision risk. 2. Although the incidence rate of bird collisions with wind turbines around playas is unknown, it is generally believed that this risk may be lowered by placing turbines at greater distances from playa floors. 3. The Federal Advisory Committee Draft Recommendations for wind energy development discuss burying power lines and APLIC Guidelines: To reduce avian collisions, place low and medium voltage connecting power lines associated with the wind energy development underground to the extent possible, unless burial of the lines is prohibitively expensive (e.g., where shallow bedrock exists) or where greater adverse impacts to biological resources would result: b. Overhead lines may be used when the lines parallel tree lines, employ bird flight diverters, or are otherwise screened so that collision risk is reduced. c. Above- ground low and medium voltage lines, transformers and conductors should follow the 2006 or most recent APLIC Suggested Practices for Avian Protection on Power Lines. (Chapter 3, page 44; Draft Recommendations 3/2010) 12 In areas with high densities of wetlands, consider burying electrical/collection lines where feasible to decrease risk of avian collisions during take-off and landing. However, steps will need to be taken to minimize impacts to the clay layer if lines are buried under a playa. Application of bird flight diverters and adherence to the Avian and Power Line Interaction Committee guidelines, 13 in situations where it is not possible or practicable to bury collection or transmission lines, may decrease likelihood of collision and electrocution. Conservation Offsets (Mitigation) True Offsets (actions that increase habitat quantity): 17 December 2010 Page 2

3 Playas cannot be created; therefore, conservation options are limited to conserving existing playas and restoring degraded playas. Mitigation and Other Offset Options: These mitigation and offset options are designed to improve the biological function of existing playas and may replace functional loss due to development on or near a playa. 1. Restoration of playa hydroperiod in previously impacted playas may be accomplished through removal of sediment from playa floor, filling pits, blocking surface drains, or removing other human modifications. If sediment is removed, care must be taken not to break through the clay layer. 2. Creation or maintenance of a properly-managed native-grass buffer zone around playas has been shown to protect playas from sedimentation. The preferable option is watershed enrollments or some mutually agreed upon (between state wildlife biologists and wind energy developers) ratio of buffer area to playa area. The recommended buffer width is 98 feet (30m) 3,14 3. Removal of large woody vegetation from in and around the playa will enhance habitat for many bird species. 4. Conservation easements on playas and surrounding land and/or playa complexes may be purchased and restored similar to 1, 2 and 3 above. 5. Water availability may be improved for a variety of wetland dependent birds by installing a well and employing moist-soil management techniques in previously impacted playas. Moist-soil management is the flooding and gradual drawdown of water in a wetland designed to increase habitat and promote vegetative growth for foraging for wetland dependent birds. 6. In some cases agricultural fields can be managed to lessen food availability, such as when waste grain is plowed under or non-preferred food sources are planted. Acknowledgments This BMP was originally drafted by Anne Bartuszevige, Conservation Science Director at the Playa Lakes Joint Venture. David Haukos, Bill Johnson, Ted LaGrange, and Loren Smith provided valuable scientific review of this document. The final draft of this BMP is a result of a collaborative review by CRCC participants. Additional Information and Resources Consulted: 1. For additional information go to The website lists Local Conservation Partnerships which can help facilitate conservation in specific areas. 2. Cariveau, A.B. and D. Pavlacky Assessment and conservation of playas in eastern Colorado: Final report to the Colorado Division of Wildlife, Playa Lakes Joint Venture, United States Environmental Protection Agency, and United States Fish and Wildlife Service. Rocky Mountain Bird Observatory, Brighton CO. 117 pp. 3. Smith, L.M Playas of the Great Plains. University of Texas Press, Austin, TX. 4. Johnson, W.P., M.B. Rice, D.A. Haukos, and P.P. Thorpe Midwinter occurrence of inundated playa wetlands in the Texas High Plains. Abstract to North American Duck Symposium, Toronto, Ontario, Canada. 5. Cariveau, A.B., L.A. Johnson, and R.A. Sparks Biological inventory and evaluation of conservation strategies in southwest playa wetlands: Final report to the Nebraska Game and Parks Commission and the Playa Lakes Joint Venture. Rocky Mountain Bird Observatory, Brighton, CO, 44pp. 6. Cariveau, A.B. and L. Johnson Assessment and conservation of playas in eastern Colorado: Neotropical Migratory Bird Conservation Act Final Report to the United States Fish and Wildlife Service, Rocky Mountain Bird Observatory, Brighton, CO, 42pp. 7. Daily movements of Northern Pintails are km ( miles). During the hunting season movements increase to km ( miles). (Moon, J.A Survival, Movements and Habitat Use of Female Northern Pintails in the Playa Lakes Region. M.S. Thesis, Texas Tech University. 216 p.) 17 December 2010 Page 3

4 8. A complex of playas is when playas are at a higher density in an area than the overall occurrence rate for that region. 9. Gurdak, J.J. and C.D. Roe Recharge rates and chemistry beneath playas of the high plains aquifer A literature review and synthesis. U.S. Geological Survey Circular 1333, 39 p. 10. Clay layer depth and thickness are highly variable and dependent upon on playa size, location, soil-type and other local conditions. Depth of Randall clay generally is from more than 14 feet in playa lake proper to less than 12 inches at rim (Smith, S.J., B.A. Stweart, A.N. Sharpley, J.W. Naney, T. McDonald, M.G. Hickey, and J.M. Sweeten Nitrate and other nutrients associated with playa storage of feedlot wastes. Report for Texas Agricultural Extension Service, College Station, TX. 21 pp. ) 11. Cariveau, A.B. and D. Pavlacky Floristic quality assessment and wildlife habitat assessment of playas in eastern Colorado: final report to the United States Environmental Protection Agency and the Colorado Division of Wildlife, Rocky Mountain Bird Observatory, Brighton, CO, 97 pp. 12. U.S. Fish and Wildlife Service Wind Turbine Recommendations Advisory Committee. March 4, APLIC (Avian Power Line Interaction Committee) R. Harness contributing author to: Suggested Practices for Avian Protection on Power Lines: State of the Art in Edison Electric Institute, APLIC, and the California Energy Commission. Washington, D.C. and Sacramento, CA. 14. Skagen, S.K., C.P. Melcher, and D.A. Haukos Reducing sedimentation of depressional wetlands in agricultural landscapes. Wetlands 28: December 2010 Page 4

5 Table 1 From Cariveau, A.B. and D. Pavlacky December 2010 Page 5

6 Figure 1: Map of playa complexes in eastern Colorado. The grey or blue shading is an indication of the complexes delineated by the desktop modeling process using biological data relevant to Northern Pintails, a waterfowl species that often uses playas during migration and winter. Playas and playa complexes are equally important for conservation. The boundaries of the playa complex polygons do not indicate a setback distance (buffer) for development activities nor do they indicate a go or no-go zone. The purpose of this map is to provide a visual representation of what is meant by playa complexes in the text above. 17 December 2010 Page 6