Recharge rates and chemistry beneath playas of the High Plains aquifer: A literature review and synthesis

Abstract

Playas are ephemeral, closed-basin wetlands that are important zones of recharge to the High Plains (or Ogallala) aquifer and critical habitat for birds and other wildlife in the otherwise semiarid, shortgrass prairie and agricultural landscape. The ephemeral nature of playas, low regional recharge rates, and a strong reliance on ground water from the High Plains aquifer has prompted many questions regarding the contribution of recharge from playas to the regional aquifer. Considerable scientific debate has led to more than 175 publications about the potential for water to infiltrate the relatively impermeable playa floors and subsequently recharge the High Plains aquifer. Since the early 1900s, many conceptual models about recharge beneath playas have been proposed. Some early conceptual models indicate that playas are evaporative pans that do not allow recharge beneath playas, whereas other more recent models indicate that playas are effective recharge basins. A variety of data supports various aspects of these competing conceptual models. The competing conceptual models have developed because of the sporadic nature of rainfall to the region, the large number of playas in the region (more than 66,000), a range of physical characteristics in playas, the relatively thick unsaturated zones (often greater than 100 feet) separating most playas from the regional water table, and the inherently uncertain nature of most methods used to estimate recharge. An accurate understanding of recharge rates beneath playas is important from the perspective of groundwater management and the sustainability of rural agricultural economies, particularly in light of the substantial water-level declines in the High Plains aquifer. Other environmental concerns, such as erosion and transport of sediment and contaminants from surrounding land and modification of playas to allow artificial recharge, also have made accurate understanding of recharge an important priority from the perspective of wetland function and habitat health, protecting groundwater quality, and the substantial costs associated with land and water management, conservation, and regulation. To address these questions and concerns, the U.S. Geological Survey, in cooperation with the Playa Lakes Joint Venture, present a review and synthesis of the more than

Late Quaternary environmental reconstructions of playa-lunette system evolution on the central High Plains of Kansas, United States

“…Dissolution was likely more important during initial playa development, though it is still occurring based on infi ltration rates one to two orders of magnitude greater within playas compared to interplayas (Gurdak and Roe, 2009). Dissolution is also likely more important during periods of higher effective precipitation, while defl ation dominates during arid periods.…”

“…These data provide new information on the geomorphic response of playa-lunette systems to past climate changes and improve our understanding of the ways in which playalunette systems may respond to climate change in the future. Understanding playa-lunette system response is essential because these systems provide a host of essential functions, such as groundwater recharge, surface-water storage, wetland habitat, nutrient cycling, particulate retention, and preservation of archaeological material (Campbell et al, 2007;Gurdak and Roe, 2009;Haukos and Smith, 1994;Luo et al, 1999;Smith, 2003).…”

Factors Influencing the Occurrence of Inundated Playa Wetlands During Winter on the Texas High Plains

“…Playas typically fill following intense, localized precipitation events and because of the lack of a direct hydrologic connection to groundwater, these dynamic wetlands dry between precipitation events; at times, being dry for several years between inundation events. Therefore, playas are the principal floodwater conveyance and storage system in the THP and only focused recharge points for the underlying Ogallala Aquifer (Osterkamp and Wood 1987;Gurdak and Roe 2009). Other ecological functions include refugia for native plants (Haukos and Smith 2004), providing natural wildlife habitat (Haukos and Smith 1994), and biomass production Smith 1993, 2006).…”

Vegetation and Land use Impact on Water Loss Rate in Playas of the Southern High Plains, USA

“…Alternatively, Zartman et al (1994) and Wood et al (1997) suggested that long-term infiltration, and thus recharge, may occur within the playa basin via macropores. While there is no consensus on infiltration location and process in playas, the sediment from upland watersheds further complicates the situation (Gurdak and Roe 2009). It is unclear whether the increased sediment loads in playas within cropland watersheds reduce water flow into the annular areas and macropores.…”