From the site: "This report describes new digital maps delineating areas of the United States, including Puerto Rico and the U.S. Virgin Islands, having karst or the potential for development of karst and pseudokarst. These maps show areas underlain by soluble rocks and also by volcanic rocks, sedimentary deposits, and permafrost that have potential for karst or pseudokarst development. All 50 States contain rocks with potential for karst development, and about 18 percent of their area is underlain by soluble rocks having karst or the potential for development of karst features. The areas of soluble rocks shown are based primarily on selection from State geologic maps of rock units containing significant amounts of carbonate or evaporite minerals. Areas underlain by soluble rocks are further classified by general climate setting, degree of induration, and degree of exposure. Areas having potential for volcanic pseudokarst are those underlain chiefly by basaltic-flow rocks no older than Miocene in age. Areas with potential for pseudokarst features in sedimentary rocks are in relatively unconsolidated rocks from which pseudokarst features, such as piping caves, have been reported. Areas having potential for development of thermokarst features, mapped exclusively in Alaska, contain permafrost in relatively thick surficial deposits containing ground ice. This report includes a GIS database with links from the map unit polygons to online geologic unit descriptions."

Several natural and anthropogenic tracers have been used to evaluate groundwater residence time within a karstic limestone aquifer in southeastern New Mexico, USA. Natural groundwater discharge occurs in the lower Pecos Valley from a region of karst springs, wetlands and sinkhole lakes at Bitter Lake National Wildlife Refuge,on the northeast margin of the Roswell Artesian Basin. The springs and sinkholes are formed in gypsum bedrock that serves as a leaky confining unit for an artesian aquifer in the underlying San Andres limestone. Because wetlands on the Refuge provide habitat for threatened and endangered species, there is concern about the potential for contamination by anthropogenic activity in the aquifer recharge area. Estimates of the time required for groundwater to travel through the artesian aquifer vary widely because of uncertainties regarding karst conduit flow. A better understanding of groundwater residence time is required to make informed decisions about management of water resources and wildlife habitat at Bitter Lake. Results indicate that the artesian aquifer contains a significant component of water recharged within the last 10 to 50 years, combined with pre-modern groundwater originating from deeper underlying aquifers, some of which may be indirectly sourced from the high Sacramento Mountains to the west.

In 2005, the New Mexico Bureau of Geology and Mineral Resources initiated a hydrogeology study in the southern Sacramento Mountains with funding from legislative appropriations through the Otero Soil and Water Conservation district. The project was initiated and research funding was continued because of concerns about future water resources for local communities in the southern Sacramento Mountains. Over the past decade, water managers and residents have observed decreasing spring discharge and streamflow in the area, and significant declines of water-levels in wells. Land and resource managers have expressed interest in the potential to increase water availability by thinning woodlands in the mountain watersheds. The focus of this investigation has been to characterize the hydrogeologic framework of the southern Sacramento Mountains and surrounding areas. The results of this study also provide a foundation to assess the impact of tree thinning on groundwater-levels, spring discharge and streamflow in an ongoing study of a small mountain watershed.

From the site: "Karst regions derived from 1968 geological map of West Virginia. In 1968 the West Virginia Geological and Economic Survey (WVGES) published a State Geologic Map. The topographic base was compiled from Army Map Service 1:250,000 scale map sheets. In 1998 the WV Division of Environmental Protection (WVDEP) scanned the hardcopy geologic maps at 300 dpi, 8-bit color, and then georeferenced them. Rock unit boundaries were digitized off the images and attributed by WVDEP. The USGS-Water Resources Division later revised the attributes of large water bodies and georeferenced the datum to NAD83. The WV Bureau of Public Health extracted the limestone and dolomite formations from the statewide geologic coverage to create a separate karst GIS coverage."