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More than 70 individual VOCs were identified in the leachate plume of a closed municipal landfill. Concentrations were low when compared with data published for other landfills, and total VOCs accounted for less than 0.1% of the total dissolved organic carbon. The VOC concentrations in the core of the anoxic leachate plume are variable, but in all cases they were found to be near or below detection limits within 200 m of the landfall. In contrast to the VOCs, the distributions of chloride ion, a conservative tracer, and nonvolatile dissolved organic carbon, indicate little dilution over the same distance. Thus, natural attentuation processes are effectively limiting migration of the VOC plume. The distribution of...
Categories: Publication; Types: Citation; Tags: Groundwater
What are current conditions for important park natural resources? What are the critical data and knowledge gaps? What are some of the factors that are influencing park resource conditions? Natural Resource Condition Assessments (NRCAs) evaluate and report on the above for a subset of important natural resources in national park units (hereafter, parks). Focal study resources and indicators are selected on a park-by-park basis, guided by use of structured resource assessment and reporting frameworks. Considerations include park resource setting and enabling legislation (what are this park's most important natural resources?) and presently available data and expertise (what can be evaluated at this time?). In addition...
Natural landscapes in the Southwestern United States are changing. In recent decades, rising temperatures and drought have led to drier conditions, contributed to large-scale ecological impacts, and affected many plant and animal species across the region. The current and future trajectory of climate change underscores the need for managers and conservation professionals to understand the impacts of these patterns on natural resources. In this regional assessment of the Southwest Climate Change Initiative, we evaluate changes in annual average temperatures from 1951–2006 across major habitats and large watersheds and compare these changes to the number of species of conservation concern that are found within these...
El Espacio Digital Geográfico (ESDIG) de la SEMARNAT, muestra en mapas información sobre las características ambientales y sociales del país en temas como vegetación, uso del suelo, cuerpos de agua, suelos, clima, población, entre otros, así como de los resultados de programas ambientales y sociales dedicados al aprovechamiento, conservación y recuperación de los ecosistemas naturales de México. Los mapas desplegados son extraídos de la base de datos geográfica del SNIARN. La información contenida en ésta base ha sido generada por diferentes áreas de la Semarnat, sus órganos desconcentrados y descentralizados, así como también por el INEGI y diversas dependencias del Gobierno Federal.
A two-dimensional finite element model was used to simulate the groundwater recovery process under various surface mining situations. The simulation results were used to predict the rate at which soil settlement takes place. It was found that the groundwater recovery process is very fast immediately after mine closure and cessation of dewatering programmes; a significant part of mine land settlement can be measured at such times. This paper presents a method for deriving the relationship between the re-establishment of the natural groundwater regime to its equilibrium position as existed prior to the commencement of mining operations and mine spoil settlement.
Summary A detailed local-scale monitoring network was used to assess CFC distribution in an unconfined sand aquifer in southwestern Ontario where the zone of 1–5-year-old groundwater was known with certainty because of prior use of a bromide tracer. Groundwater ⩽5 years old was confined to an aerobic zone at ⩽5 m depth and had CFC concentrations consistent with modern atmospheric mixing ratios at recharge temperatures of 7–11 °C, as was observed in the 3-m thick vadose zone at the site. At depths below 6 m, the groundwater became progressively more reducing, however, with a denitrifying horizon at 6–7 m depth, and a Mn and Fe reducing zone below 7 m depth. In the anaerobic zone, 3H/3He ratios indicated that groundwater-age...
We examined the chemical reactions influencing dissolved concentrations, speciation, and transport of naturally occurring arsenic (As) in a shallow, sand and gravel aquifer with distinct geochemical zones resulting from land disposal of dilute sewage effluent. The principal geochemical zones were: (1) the uncontaminated zone above the sewage plume [350 µM dissolved oxygen (DO), pH 5.9]; (2) the suboxic zone (5 µM DO, pH 6.2, elevated concentrations of sewage-derived phosphate and nitrate); and (3) the anoxic zone [dissolved iron(II) 100–300 µM, pH 6.5–6.9, elevated concentrations of sewage-derived phosphate]. Sediments are comprised of greater than 90% quartz but the surfaces of quartz and other mineral grains are...
This study proposes the use of several problems of unstable steady state convection with variable fluid density in a porous layer of infinite horizontal extent as two-dimensional (2-D) test cases for density-dependent groundwater flow and solute transport simulators. Unlike existing density-dependent model benchmarks, these problems have well-defined stability criteria that are determined analytically. These analytical stability indicators can be compared with numerical model results to test the ability of a code to accurately simulate buoyancy driven flow and diffusion. The basic analytical solution is for a horizontally infinite fluid-filled porous layer in which fluid density decreases with depth. The proposed...
This map layer contains the shallowest principal aquifers of the conterminous United States, Hawaii, Puerto Rico, and the U.S. Virgin Islands, portrayed as polygons. The map layer was developed as part of the effort to produce the maps published at 1:2,500,000 in the printed series "Ground Water Atlas of the United States". The published maps contain base and cultural features not included in these data. This is a replacement for the July 1998 map layer called Principal Aquifers of the 48 Conterminous United States.
In this paper, we present a flexible approach for simulating one- and two-dimensional routing of surface water using a numerical surface water routing (SWR) code implicitly coupled to the groundwater-flow process in MODFLOW. Surface water routing in SWR can be simulated using a diffusive-wave approximation of the Saint-Venant equations and/or a simplified level-pool approach. SWR can account for surface water flow controlled by backwater conditions caused by small water-surface gradients or surface water control structures. A number of typical surface water control structures, such as culverts, weirs, and gates, can be represented, and it is possible to implement operational rules to manage surface water stages...
Categories: Publication; Types: Citation; Tags: Groundwater
More than 10 billion gallons (38 × 106 m3) of acid industrial liquid waste has been injected in about 11 years under high pressure into a saline-water-filled part of a limestone aquifer of low transmissivity between 1,400 and 1,700 feet (430 and 520 m) below land surface near Pensacola, Florida. A similar waste disposal system is planned for the same zone at a site about 8.5 miles (13.7 km) to the east. The injection zone is the lower limestone of the Floridan aquifer. The lower limestone is overlain by a confining layer of plastic clay about 220 feet (67 m) thick at the active injection site and underlain by another confining layer of shale and clay. The upper confining layer is overlain by the upper limestone...
Categories: Publication; Types: Citation; Tags: Groundwater
This community serves to document data and analysis collected by researchers within the Upper Midwest Water Science Center whose mission is to collect high-quality hydrologic data and conduct unbiased, scientifically sound studies of water resources within the Great Lakes and Upper Mississippi Basins. We strive to meet the changing needs of those who use our information—from the distribution, availability, and quality of our water resources to topic-oriented research that addresses current hydrological issues.
The Conservation Reserve Program (CRP) is one of the largest programs of the U.S. Department of Agriculture (USDA) that encourages farmers and ranchers to establish resource-conserving vegetative covers to address soil, water and related resource issues on their lands. This research study examines the relationship between the CRP and the changes in the groundwater levels within Texas County in the Oklahoma Panhandle region. The region overlies the central portion of the High Plains Aquifer that has shown significant decline in groundwater levels, due largely to the development of irrigated agriculture. Using the calibrated SWAT (Soil and Water Assessment Tool) model and GIS-based analysis, a significant spatial...
Significant changes in nitrogen loads to Jamaica Bay have likely occurred with progressive improvements to Water Pollution Control Plants (WCWPs) that discharge into the Bay. Data available from the New York City Department of Environmental Protection and others will be used to determine loads from WPCPs, combined sewer overflows, and the atmosphere. Selected wells within the USGS water quality database, including those near the landfills that are immediately adjacent to Jamaica Bay, will be used to determine concentrations of nutrients in shallow ground water that enter the bay from ground water seepage. To facilitate evaluation of ground water loads, an existing USGS Finite element model that simulates sub...
This dataset contains field measurements of lakebed groundwater temperatures collected during three surveys in July 2008, August 2014, and August 2015, by using a handheld thermocouple probe and GPS at a permeable reactive barrier at Ashumet Pond, Falmouth, MA. The comma-separated file includes unique site identifiers, locations of measurement points, temperatures, dates, and types of measurement (groundwater, surface water, or control). Also included are ESRI raster datasets for each measurement date for (1) interpolated lakebed groundwater temperatures, and (2) interpolated lakebed groundwater temperatures normalized to the surface water temperature at the time of measurement. This data release is provided...

map background search result map search result map Principal Aquifers of the 48 Conterminous United States, Hawaii, Puerto Rico, and the U.S. Virgin Islands Natural Resource Condition Assessments Managing Changing Landscapes in the Southwestern United States Espacio Digital Geográfico (ESDIG) Assessment of Nutrient Loading to Jamaica Bay, Gateway National Recreation Area, New York 04_Field measurements of lakebed groundwater temperatures by using a thermocouple probe, July 2008, August 2014, and August 2015, Falmouth, MA Upper Midwest Water Science Center Assessment of Nutrient Loading to Jamaica Bay, Gateway National Recreation Area, New York Upper Midwest Water Science Center Managing Changing Landscapes in the Southwestern United States Espacio Digital Geográfico (ESDIG) Principal Aquifers of the 48 Conterminous United States, Hawaii, Puerto Rico, and the U.S. Virgin Islands Natural Resource Condition Assessments