SEARCH · Search USGS

Results for “Soil Systems”

Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 217 records · Page 12Linked to original sources

USGS2017

Isotopic Approach to Soil Carbonate Dynamics and Implications for Paleoclimatic Interpretations

The radiocarbon content and stable isotope composition of soil carbonate are best described by a dynamic system in which isotopic reequilibration occurs as a result of recurrent dissolution and reprecipitation. Depth of water penetration into the soil profile, as well as soil age, determines the degree of carbonate isotope reequilibration. We measured ??13C, ??18O and radiocarbon content of gravel rinds and fine (<2 mm) carbonate in soils of 3 .different ages (1000, 3800, and 6300 14 C yr B.P.) to assess the degree to which they record and preserve a climatic signal. In soils developing in deposits independently dated at 3800 and 6300 radiocarbon yr B.P., carbonate radiocarbon content above 40 cm depth suggests continual dissolution and reprecipitation, presumably due to frequent wetting events. Between 40 and 90 cm depth, fine carbonate is dissolved and precipitated as rinds that are not redissolved subsequently. Below 90 cm depth in these soils, radiocarbon content indicates that inherited, fine carbonate undergoes little dissolution and reprecipitation. In the 3800- and 6300-yr-old soils, ??13C in rind and fine carbonate follows a decreasing trend with depth, apparently in equilibrium with modern soil gas, as predicted by a diffusive model for soil CO2. ??18O also decreases with depth due to greater evaporative enrichment above 50 cm depth. In contrast, carbonate isotopes in a 1000-yr-old deposit do not reflect modern conditions even in surficial horizons; this soil has not undergone significant pedogenesis. There appears to be a lag of at least 1000 but less than 3800 yr before carbonate inherited with parent material is modified by ambient climatic conditions. Although small amounts of carbonate are inherited with the parent material, the rate of pedogenic carbonate accumulation indicates that Ca is derived primarily from eolian and rainfall sources. A model describing carbonate input and radiocarbon decay suggests that fine carbonate below 90 cm is mostly detrital (inherited) and that carbonate rinds have been forming pedogenically at a constant rate since alluvial fans were deposited.

Quaternary Research↗

USGS2020

A pan-African high-resolution drought index dataset

Droughts in Africa cause severe problems, such as crop failure, food shortages, famine, epidemics and even mass migration. To minimize the effects of drought on water and food security on Africa, a high-resolution drought dataset is essential to establish robust drought hazard probabilities and to assess drought vulnerability considering a multi- and cross-sectional perspective that includes crops, hydrological systems, rangeland and environmental systems. Such assessments are essential for policymakers, their advisors and other stakeholders to respond to the pressing humanitarian issues caused by these environmental hazards. In this study, a high spatial resolution Standardized Precipitation-Evapotranspiration Index (SPEI) drought dataset is presented to support these assessments. We compute historical SPEI data based on Climate Hazards group InfraRed Precipitation with Station data (CHIRPS) precipitation estimates and Global Land Evaporation Amsterdam Model (GLEAM) potential evaporation estimates. The high-resolution SPEI dataset (SPEI-HR) presented here spans from 1981 to 2016 (36 years) with 5 km spatial resolution over the whole of Africa. To facilitate the diagnosis of droughts of different durations, accumulation periods from 1 to 48 months are provided. The quality of the resulting dataset was compared with coarse-resolution SPEI based on Climatic Research Unit (CRU) Time Series (TS) datasets, Normalized Difference Vegetation Index (NDVI) calculated from the Global Inventory Monitoring and Modeling System (GIMMS) project and root zone soil moisture modelled by GLEAM. Agreement found between coarse-resolution SPEI from CRU TS (SPEI-CRU) and the developed SPEI-HR provides confidence in the estimation of temporal and spatial variability of droughts in Africa with SPEI-HR. In addition, agreement of SPEI-HR versus NDVI and root zone soil moisture – with an average correlation coefficient ( R ) of 0.54 and 0.77, respectively – further implies that SPEI-HR can provide valuable information for the study of drought-related processes and societal impacts at sub-basin and district scales in Africa. The dataset is archived in Centre for Environmental Data Analysis (CEDA) via the following link: https://doi.org/10.5285/bbdfd09a04304158b366777eba0d2aeb (Peng et al., 2019a).

Earth System Science Data↗

USGS1985

Mechanistic roles of soil humus and minerals in the sorption of nonionic organic compounds from aqueous and organic solutions

Mechanistic roles of soil humus and soil minerals and their contributions to soil sorption of nonionic organic compounds from aqueous and organic solutions are illustrated. Parathion and lindane are used as model solutes on two soils that differ greatly in their humic and mineral contents. In aqueous systems, observed sorptive characteristics suggest that solute partitioning into the soil-humic phase is the primary mechanism of soil uptake. By contrast, data obtained from organic solutions on dehydrated soil partitioning into humic phase and adsorption by soil minerals is influenced by the soil-moisture content and by the solvent medium from which the solute is sorbed.

Organic Geochemistry↗

USGS2011

Hydrologic assessment of three drainage basins in the Pinelands of southern New Jersey, 2004-06

The New Jersey Pinelands is an ecologically diverse area in the southern New Jersey Coastal Plain, most of which overlies the Kirkwood-Cohansey aquifer system. The demand for groundwater from this aquifer system is increasing as local development increases. Because any increase in groundwater withdrawals has the potential to affect streamflows and wetland water levels, and ultimately threaten the ecological health and diversity of the Pinelands ecosystem, the U.S. Geological Survey, in cooperation with the New Jersey Pinelands Commission, began a multi-phase hydrologic investigation in 2004 to characterize the hydrologic system supporting the aquatic and wetland communities of the New Jersey Pinelands area (Pinelands). The current investigation of the hydrology of three representative drainage basins in the Pinelands (Albertson Brook, McDonalds Branch, and Morses Mill Stream basins) included a compilation of existing data; collection of water-level and streamflow data; mapping of the water-table altitude and depth to the water table; and analyses of water-level and streamflow variability, subsurface gradients and flow patterns, and water budgets. During 2004-06, a hydrologic database of existing and new data from wells and stream sites was compiled. Methods of data collection and analysis were defined, and data networks consisting of 471 wells and 106 surface-water sites were established. Hydrographs from 26 water-level-monitoring wells and four streamflow-gaging stations were analyzed to show the response of water levels and streamflow to precipitation and recharge with respect to the locations of these wells and streams within each basin. Water-level hydrographs show varying hydraulic gradients and flow potentials, and indicate that responses to recharge events vary with well depth and proximity to recharge and discharge areas. Results of the investigation provide a detailed characterization of hydrologic conditions, processes, and relations among the components of the hydrologic cycle in the Pinelands. In the Pinelands, recharge replenishes the aquifer system and contributes to groundwater flow, most of which moves to wetlands and surface water where natural discharge occurs. Some groundwater flow is intercepted by supply wells. Recharge rates generally are highest during the non-growing season and are inversely related to evapotranspiration. Analysis of subsurface hydraulic gradients, water-table fluctuations, and streamflow variability indicates a strong linkage between groundwater and wetlands, lakes and streams. Gradient analysis indicates that most wetlands are in groundwater discharge areas, but some wetlands are in groundwater recharge areas. The depth to the water table ranges from zero at surface-water features up to about 10 meters in topographically high areas. Depth to water fluctuates seasonally, and the magnitude of these fluctuations generally increases with distance from surface water. Variations in the permeability of the soils and sediments of the aquifer system strongly affect patterns of water movement through the subsurface and the interaction of groundwater with wetlands, lakes and streams. Mean annual streamflow during 2004-06 ranged from 83 to 106 percent of the long-term mean annual discharge, indicating that the data-collection period can be considered representative of average conditions. Measurements of groundwater levels, stream stage, and stream discharge and locations of start-of-flow are illustrated in basin-wide maps of water-table altitude, depth to the water table, and stream base flow during the period. Water-level data collected along 15 hydrologic transects that span the range of environments from uplands through wetlands to surface water were used to determine hydraulic gradients, potential flow directions, and areas of recharge and discharge. These data provide information about the localized interactions of groundwater with wetlands and surface water. Wetlands were categorized with r

New Jersey↗

USGS2019

POLARIS properties: 30-meter probabilistic maps of soil properties over the contiguous United States

Soils play a critical role in the cycling of water, energy, and carbon in the Earth system. Until recently, due primarily to a lack of soil property maps of a sufficiently high‐quality and spatial detail, a minor emphasis has been placed on providing high‐resolution measured soil parameter estimates for land surface models and hydrologic models. This study introduces Probabilistic Remapping of SSURGO (POLARIS) soil properties—a database of 30‐m probabilistic soil property maps over the contiguous United States (CONUS). The mapped variables over CONUS include soil texture, organic matter, pH, saturated hydraulic conductivity, Brooks‐Corey and Van Genuchten water retention curve parameters, bulk density, and saturated water content. POLARIS soil properties was assembled by (1) depth harmonizing and aggregating the pedons in the National Cooperative Soil Survey Soil Characterization Database and the components in Soil Survey Geographic Database into a database of 21,481 different soil series, each soil series having its own vertical profiles of different soil properties, (2) pruning the original POLARIS soil series maps using conventional soil maps to improve soil series prediction accuracy, and (3) merging the assembled soil series databases with the pruned POLARIS soil series maps to construct the soil property maps over CONUS. POLARIS soil properties includes 100‐bin histograms for each layer and variable per grid cell and a series of summary statistics at 30‐, 300‐, and 3,000‐m spatial resolution. Evaluation of POLARIS soil properties using in situ measurements shows an average R2 of 0.41, normalized root‐mean‐square error of 12%, and a normalized mean absolute error of 8.8%.

Water Resources Research↗

USGS2014

Evaluating abiotic influences on soil salinity of inland managed wetlands and agricultural croplands in a semi-arid environment

Agriculture and moist-soil management are important management techniques used on wildlife refuges to provide adequate energy for migrant waterbirds. In semi-arid systems, the accumulation of soluble salts throughout the soil profile can limit total production of wetland plants and agronomic crops and thus jeopardize meeting waterbird energy needs. This study evaluates the effect of distinct hydrologic regimes associated with moist-soil management and agricultural production on salt accumulation in a semi-arid floodplain. We hypothesized that the frequency of flooding and quantity of floodwater in a moist-soil management hydroperiod results in a less saline soil profile compared to profiles under traditional agricultural management. Findings showed that agricultural croplands differed ( p -value < 0.001, df = 9) in quantities of total soluble salts (TSS) compared to moist-soil impoundments and contained greater concentrations (TSS range = 1,160-1,750 (mg kg-1)) at depth greater than 55 cm below the surface of the profile, while moist-soil impoundments contained lower concentrations (TSS range = 307-531 (mg kg-1)) at the same depths. Increased salts in agricultural may be attributed to the lack of leaching afforded by smaller summer irrigations while larger periodic flooding events in winter and summer flood irrigations in moist-soil impoundments may serve as leaching events.

Wetlands↗

USGS1996

Use of 2D and 3D GIS in well selection and interpretation of nitrate data, central Nebraska, USA

Nonpoint-source contamination of the principal aquifers in a 7800 km2 area of central Nebraska was evaluated utilizing aquifer condition, well depth, soil type, and physiographical and land use settings. A two-dimensional geographical information system linked with a three-dimensional geological visualization and analytical program was used in the random selection of acceptable wells for the monitoring of nitrate concentrations in groundwater. Locations of existing wells were super-imposed on the three-dimensional geological block diagram and more than 200 wells randomly were selected for monitoring. The three-dimensional system also was used to show three-dimensional contours of nitrate concentrations that can be used interactively to determine the volumetric percentage of an aquifer that contains nitrate concentrations exceeding a specified threshold. The two-dimensional geographical information system was used in comparing nitrate concentrations in differing physiographical, soil, and land use settings. Preliminary results suggest that approximately 6% (volumetric) of water in the High Plains aquifer has nitrate concentrations above the US Environmental Protection Agency Maximum Contaminant Level of 10 mg 1-1 as N.

IAHS-AISH Publication↗

USGS1990

Water movement through an experimental soil liner

A field-scale soil liner was constructed to test whether compacted soil barriers in cover and liner systems could be built to meet the U.S. EPA saturated hydraulic conductivity requirement (⩽ 1 × 10 −7 cm s −1 ). The 8 × 15 × 0.9 m liner was constructed in 15 cm compacted lifts using a 20,037 kg pad-foot compactor and standard engineering practices. Water infiltration into the liner has been monitored for one year. Monitoring will continue until water break through at the base of the liner occurs. Estimated saturated hydraulic conductivities were 2.5 × 10 −9 , 4.0 × 10 −8 , and 5.0 × 10 −8 cm s −1 based on measurements of water infiltration into the liner by large- and small-ring infiltrometers and a water balance analysis, respectively. Also investigated in this research was the variability of the liner's hydraulic properties and estimates of the transit times for water and tracers. Small variances exhibited by small-ring flux data suggested that the liner was homogeneous with respect to infiltration fluxes. The predictions of water and tracer breakthrough at the base of the liner ranged from 2.4–12.6 y, depending on the method of calculation and assumptions made. The liner appeared to be saturated to a depth between 18 and 33 cm at the end of the first year of monitoring. Transit time calculations cannot be verified yet, since breakthrough has not occurred. The work conducted so far indicates that compacted soil barriers can be constructed to meet the saturated hydraulic conductivity requirement established by the U.S. EPA.

Waste Management and Research↗

USGS2024

Season of grazing interacts with soil texture, selecting for associations of biocrust morphogroups

Livestock grazing, a widespread land use in semi-arid systems, is often placed in opposition to the perpetuation of biological soil crusts (“biocrusts”: lichens, mosses, and algal crusts including cyanobacteria) that live on the soil surface and provide ecosystem functions. The composition of biocrusts and vascular plants varies with climate, soils, and disturbance. In general, ruderal mosses and light algal crusts make up greater proportions of biocrusts in the presence of disturbance, although morphogroups of biocrusts respond differently to various disturbances. It is unknown if there are scenarios under which grazing can occur and ruderal components of biocrust could be maintained. We examine the hypothesis that soil surface texture-moisture interactions influence the ability of biocrusts to withstand trampling, reasoning that finer-textured soils are firmer (therefore serving as a better substrate for biocrusts) when dry and that coarser-textured are firmer when wet. We test these relationships within Birds of Prey, National Conservation Area (Boise, Idaho, USA). Results demonstrate two associations of biocrusts, dependent on season of grazing: one dominated by light algal crusts and lichens that frequently occurs with wet season grazing, and a second dominated by tall mosses and cup lichens that frequently occurs with dry season grazing. High cover of the invasive annual grass, Bromus tectorum (L.) was observed on sites with coarse-textured soils, and high sand content, that are grazed at relatively high intensities, creating unstable surfaces, and likely putting biocrusts at greater susceptibility to trampling. Results suggest that livestock management that accounts for soil texture and moisture could be used to maintain cover of ruderal biocrusts on fine-textured soils, that are grazed in the dry season, at low intensity. We discuss our findings in the context of managing for species of interest. Our findings are timely as varying the season of grazing is increasingly discussed as a means of favoring desirable native perennial grasses. Although ruderal morphogroups of biocrusts are not interpreted as having equivalent ecosystem functions compared to intact biocrusts, their contributions to soil stability, fertility, hydrology, and weed abatement could increase if they were more intentionally targeted by management.

Geoderma↗

USGS2024

Advanced quantitative precipitation information: Improving monitoring and forecasts of precipitation, streamflow, and coastal flooding in the San Francisco Bay area

Advanced Quantitative Precipitation Information (AQPI) is a synergistic project that combines observations and models to improve monitoring and forecasts of precipitation, streamflow, and coastal flooding in the San Francisco Bay Area. As an experimental system, AQPI leverages more than a decade of research, innovation, and implementation of a statewide, state-of-the-art network of observations, and development of the next generation of weather and coastal forecast models. AQPI was developed as a prototype in response to requests from the water management community for improved information on precipitation, riverine, and coastal conditions to inform their decision-making processes. Observation of precipitation in the complex Bay Area landscape of California’s coastal mountain ranges is known to be a challenging problem. But, with new advanced radar network techniques, AQPI is helping fill an important observational gap for this highly populated and vulnerable metropolitan area. The prototype AQPI system consists of improved weather radar data for precipitation estimation; additional surface measurements of precipitation, streamflow, and soil moisture; and a suite of integrated forecast modeling systems to improve situational awareness about current and future water conditions from sky to sea. Together these tools will help improve emergency preparedness and public response to prevent loss of life and destruction of property during extreme storms accompanied by heavy precipitation and high coastal water levels—especially high-moisture laden atmospheric rivers. The Bay Area AQPI system could potentially be replicated in other urban regions in California, the United States, and worldwide.

California↗

USGS1995

Surface disturbances: their role in accelerating desertification

Maintaining soil stability and normal water and nutrient cycles in desert systems is critical to avoiding desertification. These particular ecosystem processes are threatened by trampling of livestock and people, and by off-road vehicle use. Soil compaction and disruption of cryptobiotic soil surfaces (composed of cyanobacteria, lichens, and mosses) can result in decreased water availability to vascular plants through decreased water infiltration and increased albedo with possible decreased precipitation. Surface disturbance may also cause accelerated soil loss through wind and water erosion and decreased diversity and abundance of soil biota. In addition, nutrient cycles can be altered through lowered nitrogen and carbon inputs and slowed decomposition of soil organic matter, resulting in lower nutrient levels in associated vascular plants. Some cold desert systems may be especially susceptible to these disruptions due to the paucity of surface-rooting vascular plants for soil stabilization, fewer nitrogen-fixing higher plants, and lower soil temperatures, which slow nutrient cycles. Desert soils may recover slowly from surface disturbances, resulting in increased vulnerability to desertification. Recovery from compaction and decreased soil stability is estimated to take several hundred years. Re-establishment rates for soil bacterial and fungal populations are not known. The nitrogen fixation capability of soil requires at least 50 years to recover. Recovery of crusts can be hampered by large amounts of moving sediment, and re-establishment can be extremely difficult in some areas. Given the sensitivity of these resources and slow recovery times, desertification threatens million of hectares of semiarid lands in the United States.

Environmental Monitoring and Assessment↗

USGS2026

Carbon sequestration along a gradient of tidal marsh degradation in response to sea level rise

Tidal marshes are considered one of the world's most efficient ecosystems for belowground organic carbon sequestration and hence climate mitigation. Marsh systems are however also vulnerable to degradation due to climate-induced sea level rise, whereby marsh vegetation conversion to open water often follows distinct spatial patterns: levees (i.e. marsh zones < 10 m from tidal creeks) show lower vulnerability of vegetation conversion to open water than basins (i.e. interior marsh zones > 30 m from creeks). Here, we use sediment cores to investigate spatial variations in organic carbon accumulation rates (OCAR) in a microtidal system (Blackwater marshes, Maryland, USA): (1) across a gradient of marsh zones with increasing marsh degradation, assessed as increasing ratio of unvegetated versus vegetated marsh area and (2) by comparing levees versus basins. We show that OCAR is up to four times higher on marsh levees than in adjacent basins. The data suggest that this is caused by spatial variation in three processes: sediment accretion rate, vegetation productivity, and sediment compaction, which are all higher on levees. Additionally, OCAR was observed to increase with increasing degree of marsh degradation in response to sea level rise. We hypothesize this may be due to more soil waterlogging in more degraded marsh zones, which may decrease carbon decomposition. Our results highlight that tidal marsh levees, in a microtidal system, are among the fastest soil organic carbon sequestration systems on Earth, and that both levees and basins sustain their carbon accumulation rate along gradients of increasing marsh degradation in response to sea level rise.

Maryland↗

USGS1987

Integration of channel and floodplain suites. I. Developmental sequence and lateral relations of alluvial paleosols.

The lower Eocene Willwood Formation of the Bighorn Basin, northwest Wyoming, consists of about 770 m of alluvial rocks that exhibit extensive mechanical and geochemical modifications resulting from Eocene pedogenesis. Willwood paleosols vary considerably in their relative degrees of maturity; maturity is defined as stage of development as a function of the amount of time required to form. Five arbitrary stages are proposed to distinguish these soils of different maturities in the Willwood Formation. Stage 1 soils, the least mature, are entisols; stage 2 and stage 3 soils are intermediate in maturity and are probably alfisols; and stage 4 and stage 5 soils, the most mature, are spodosols. These stages are not only time-progressive elements of an in situ maturation sequence for Willwood soil formation, but, in the lateral dimension, they are also usually distributed sequentially. Study of Willwood paleosols indicates that an inverse relationship exists between soil maturity and short-term sediment accumulation rate. The least mature Willwood paleosols formed in areas of relatively high net rates of sediment accumulation on 1) channel, levee, and crevasse-splay sediments of the proximal alluvial ridge, and 2) deposits filling large and small paleovalleys formed by major episodes of gullying (lowered baselevels). In contrast, the fine-grained sediments of the distal floodplain, where net sediment accumulation rates were relatively low, experienced development of much more mature soils. Soils of intermediate maturities occur in the order of their stage on intervening proximal floodplain and distal alluvial ridge sediments. Adjacent bodies of sedimentary rock that differ in their ancient soil properties because of distance from areas of relatively high sediment accumulation are denoted by the new term pedofacies . The remarkable sequence of paleosols in the Willwood Formation clearly illustrates several important principles of soil-sediment interrelationships in aggrading alluvial systems that have broad application to other deposits. This is especially true in view of the widespread distribution of paleosols in nearly all ancient fluvial rocks. Further study of Willwood paleosols will not only enable precise lateral correlation of coeval alluvial sediments, and thereby fluvial sedimentary events, from the distal to the proximal realms of the floodplain but will also contribute to increasingly informative evaluations of the nature, tempo, and mode of alluvial succession.

Journal of Sedimentary Petrology↗

USGS2018

Concentrations of pharmaceuticals and other micropollutants in groundwater downgradient from large on-site wastewater discharges

Large subsurface treatment systems (LSTS) and rapid infiltration basins (RIB) are preferred onsite wastewater treatments compared to direct discharge of treated wastewater to streams and adjacent facilities. Discharge of these wastewater treatments may result in contaminant loading to aquifers that also serve as drinking water sources downgradient from the discharge site. Until recently, few studies have characterized the contribution of micropollutants (e.g. pharmaceuticals, fragrances, flame retardants, etc.) to receiving aquifers. We conducted a pilot project to characterize the occurrence of micropollutants in groundwater downgradient from 7 on-site treatment systems in Minnesota, USA: 5 community LSTS and 2 municipal RIB. One downgradient monitoring well was sampled three times at each facility over one year. Of 223 micropollutants analyzed, 35 were detected. Total sample concentrations ranged from 90 to 4,039 ng/L. Sulfamethoxazole (antibiotic) was detected in all samples at concentrations from 7 to 965 ng/L. Other pharmaceuticals (0.12–1,000 ng/L), organophosphorus flame retardants (10–500 ng/L), and other anthropogenic chemicals (4–775 ng/L) were also detected. The numbers and concentrations of micropollutants detected were inversely related to dissolved oxygen and depth to water. Ratios of pharmaceutical concentrations to human-health screening values were <0.10 for most samples. However, concentrations of carbamazepine and sulfamethoxazole exceeded screening values at two sites. Study results illustrate that large on-site wastewater systems designed to discharge to permeable soil or shallow groundwater effectively deliver pharmaceuticals and other micropollutants to groundwater aquifers and could contribute micropollutants to drinking water via water supply wells.

Minnesota↗

USGS2006

Creation of GIS compatible, historic detailed soil data sets for the Collier and Miami-Dade Counties, Florida

When soils data are in digital format compatible with geographic information systems (GIS), a wide variety of analyses and display capabilities are afforded. Detailed information on soils that may be important to Everglades ecosystem restoration has been created in hardcopy form using traditional soils mapping techniques. However, accurate conversion of these analogue geographic data to GIS compatible information is a complicated process. Because detailed digital soils data for Southern Florida were not yet available from the US Department of Agriculture, the U.S. Geological Survey (USGS) Eastern Geographic Science Center (EGSC) developed a means for digitizing and attributing historic soil survey data for GIS analysis. This report documents that process and the two soil survey datasets created through it, one for Collier and one for Miami-Dade Counties in Florida. First, the sources for the soils data are described. Then the approach used to determine how data would be collected and organized is provided, followed by details of the spatial data collection and attribute data encoding.

Florida↗

USGS1996

Trends in chloride, dissolved-solids, and nitrate concentrations in ground water, Carson Valley and Topaz Lake Areas, Douglas County, Nevada, 1959-88

Rapid population growth in Douglas County, an area of approximately 750 square miles in west-central Nevada, has led to concern about the present and future effects of development on ground water. This report describes the results of two nonparametric statistical procedures applied to detect trends in concentrations of chloride, dissolved solids, and nitrate in ground water. The water-quality data consist of analytical results from ground-water samples collected and analyzed by the U. S. Geological Survey and ground-water-quality data provided by the Nevada Bureau of Health Protection Services for the Carson Valley and Topaz Lake areas of Douglas County, Nevada. For purposes of this study, statistical significance, expressed as the p-value, was set at 0.1. The Mann-Whitney-Wilcoxan rank-sum test detected increasing step-trends for nitrate in one of seven residential areas and for dissolved-solids concentrations throughout the study area. Decreasing step-trends for chloride and dissolved-solids concentrations were detected in the west Carson Valley area. Kendall's Tau detected monotonic trends for increasing nitrate concentrations at four domestic wells and for increasing dissolved-solids concentrations at two domestic wells. No other statistically significant trends were indicated by either test. Land-use relations to areas where increasing trends were detected suggest that the density of individual wastewater-treatment systems may exceed the capacity of soils to treat wastewater leachate.

Nevada↗

USGS2008

Shear wave velocity investigation of soil liquefaction sites from the Tangshan, China M7.8 earthquake of 1976 using active and passive surface wave methods

An initial investigation of soil liquefaction sites from the July, 28 1976 Tangshan M7.8 earthquake was conducted between 1976 and 1978 by the National Ministry of Railways, China. These data are the basis of the ‘Chinese Method’ for assessment of liquefaction potential of silty-sand deposits, and are an important component of the worldwide data set for modern probabilistic methods for assessment of soil liquefaction using Bayesian updating and system reliability tools. We revisited 26 sites identified in the maps and published 198 report of the Ministry of Railways in order to investigate these locations with a suite of active- and passive-array surface wave methods. These sites are clustered along the north coast of the Bo Hai Sea in three areas: Lutai, Tianjin; Tangshan City and outlying village, Hebei; and Luannan county, Hebei. First, we gathered and evaluated the Rayleigh wave dispersion characteristics of the ground by comparing dispersion curves from the active source harmonic wave-spectral analysis of surface waves (SASW) method and the passive array Spatial Auto-Correlation method (SPAC). The dispersive properties of the liquefied ground as measured by these two methods were found to be almost identical. These tests were hybridized and the data sets merged in order to invert of shear wave velocities for analysis of liquefaction potential using a probabilistic framework. The data from high-values of seismic intensity near Tangshan city to low-intensities distant of the event in Luannan County segregate out into clusters of liquefied and non liquefied points clearly separated by liquefaction boundary curves developed from a large global data set of 310 sites

Tangshan↗

USGS1993

Options for water-level control in developed wetlands

Wetland habitats in the United States currently are lost at a rate of 260,000 acres/year (105,218 ha/year). Consequently, water birds concentrate in fewer and smaller areas. Such concentrations may deplete food supplies and influence behavior, physiology, and survival. Continued losses increase the importance of sound management of the remaining wetlands because water birds depend on them. Human activities modified the natural hydrology of most remaining wetlands in the conterminous United States, and such hydrologic alterations frequently reduce wetland productivity. The restoration of original wetland functions and productivity often requires the development of water distribution and discharge systems to emulate natural hydrologic regimes. Construction of levees and correct placement of control structures and water-delivery and water-discharge systems are necessary to (1) create soil and water conditions for the germination of desirable plants, (2) control nuisance vegetation, (3) promote the production of invertebrates, and (4) make foods available for wildlife that depends of wetlands (Leaflets 13.2.1 and 13.4.6). This paper provides basic guidelines for the design of wetlands that benefit wildlife. If biological considerations are not incorporated into such designs, the capability of managing wetlands for water birds is reduced and costs often are greater. Although we address the development of palustrine wetlands in migration and wintering areas, many of the discussed principles are applicable to the development of other wetland types and in other locations.

Book chapter↗