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USGS2010

Displaying seismic deaggregation: The importance of the various sources

Seismic hazard deaggregation has become a standard part of probabilistic seismic hazard assessment (PSHA). The first product of PSHA is calculation of the likely severity of ground motion at a given range of annual probability levels, and this is extremely important for seismic design of structures to be built at the site under examination. However, for full analysis of proposed structural designs, engineers also need to examine scenario events to produce detailed time histories. To select such scenarios, a deaggregation of the hazard is performed, whereby the details of sources that contribute to the annual frequency of exceeding specified levels of ground motion, or P exc , are identified. A common format for such a deaggregation is shown in Figure 1 . This relates to the 475-year peak ground acceleration (pga) at Wellington, New Zealand (41.28°S 174.77°E), and shows the distribution in magnitude and distance of sources that contribute to P exc . Return period is approximately the reciprocal of P exc . Stiff soil site conditions ( Standards New Zealand 2004 ) were assumed. The analysis in Figure 1 used the interim version of the updated seismic hazard model for New Zealand ( Stirling et al. 2007 ), with the attenuation function developed by McVerry et al. (2007). Based on a Poisson time dependence model, a return period of 475 years corresponds to a 10% probability of exceedance in 50 years. From Figure 1 , it is apparent that for this site the main contribution to ground motion of this severity is from earthquakes of magnitude about 7.6 less than 10 km from the site (blue), and there is another strong contribution from larger events in the distance range 10 to 20 km (red). These correspond to the Wellington and Wairarapa faults, respectively (see Table 1 ). There are other events less than 10 km from the site and small contributions from other sources. At this site the major contributions are from specific faults nearby, which are readily identified. At sites where there is significant background seismicity, however, the plot will be much more complicated and not so easy to interpret. Figure 1 deaggregates probabilistic pga at the site; other parameters are also commonly deaggregated in the same way, in particular response spectral acceleration at a variety of natural periods. But the figure has a major shortcoming in that it represents only one return period; to obtain a full appreciation of the various contributing sources it is necessary to perform a succession of analyses to cover the full range of return periods.

Seismological Research Letters↗

USGS2023

Analysis of aquifer framework and properties, North Magee Street well field, Southampton, New York

The U.S. Geological Survey, in cooperation with the Suffolk County Water Authority, evaluated the groundwater-flow characteristics and aquifer properties of the North Magee Street well field north of the village of Southampton, New York. Characteristics and properties included groundwater-flow direction, potential groundwater-contributing areas to the well field production wells, and aquifer transmissivity and storage. The groundwater flow and aquifer properties were also evaluated to allow Suffolk County Water Authority to better assess the potential source of dissolved halocarbons (refrigerants, such as chlorofluorocarbons). The well field production wells are screened in the upper glacial aquifer and an observation well is screened in the Magothy aquifer. Based on depth and available logs, groundwater from wells screened in the upper glacial aquifer was classified as under water-table (unconfined) conditions, and groundwater from wells screened in the Magothy aquifer was classified as being under semiconfined conditions. Groundwater flows radially to the well field during production and in a northwesterly direction under the effect of the regional flow regime. A previously published particle tracking analysis identified the following recharge contributing areas nearby the well field: (1) contributing areas to surface-water bodies of the Peconic Estuary, (2) contributing areas to surface-water bodies of the South Shore Estuary Reserve, (3) a contributing area to the Atlantic Ocean, and (4) a contributing area to another Suffolk County Water Authority well field. Five other pumping well contributing areas were identified within the study area, including those of various wells pumped for golf-course irrigation. Analysis of drawdown and recovery data collected during the multiple-well aquifer test, through the application of a Neuman analytical model, provided estimates of upper glacial aquifer characteristics and properties. Inclusion of lateral aquifer boundaries was not necessary for the analysis to result in satisfactory matches with the observed water-level responses. Aquifer transmissivity was estimated to be 170,000 feet squared per day. Storativity was estimated to be 0.02 (dimensionless), and specific yield was estimated to be 0.08 (dimensionless), consistent with the inferred degree of confinement and well field characteristics.

New York↗

USGS2005

Hydrogeology and simulation of source areas of water to production wells in a colluvium-mantled carbonate-bedrock aquifer near Shippensburg, Cumberland and Franklin Counties, Pennsylvania

This report presents the results of a study by the U.S. Geological Survey in cooperation with the Shippensburg Borough Authority to evaluate the source areas of water to production wells in a colluvium-mantled carbonate-bedrock aquifer in Cumberland and Franklin Counties, Pa. The areal extent of the zone of contribution was simulated for three production wells near Shippensburg, Pa. by use of a ground-water-flow model. A 111-square-mile area was selected as the model area and includes areas of the South Mountain Section and the Great Valley Section of the Valley and Ridge Physiographic Province. Within the model area, the geologic units in the South Mountain area are predominantly metamorphic rocks and the geologic units in the Great Valley are predominantly carbonate rocks. Hydrologic and geologic information were compiled to establish a conceptual model of ground-water flow. Characteristics of aquifer materials were determined, and streamflow and water levels were measured. Streamflow measurements in November 2003 showed all streams lost water as they flowed from South Mountain over the colluvium-mantled carbonate aquifer into the Great Valley. Some streams lost more than 1 cubic foot per second to the aquifer in this area. The Shippensburg Borough Authority owns three production wells in the model area. Two wells, Cu 969 and Fr 823, are currently (2004) used as production wells and produce 500,000 and 800,000 gallons per day, respectively. Well Cu 970 is intended to be brought on line as a production well in the future. Water levels were measured in 43 wells to use for model calibration. Water-level fluctuations and geophysical logs indicated confined conditions in well Cu 970. Ground-water flow was simulated with a model that consisted of two vertical layers, with five zones in each layer. The units were hydrostratigraphic units that initially were based on geologic formations, but boundaries were adjusted during model calibration. Model calibration resulted in a root mean square error of 9.8 feet. A parameter-estimation package was used during model calibration to estimate three parameters. The parameter estimation resulted in a value of 233 feet per day for horizontal hydraulic conductivity of the highly fractured carbonate rocks and sandy colluvium in layer 1; 3.97 feet per day for horizontal hydraulic conductivity of the ridge-forming unit in layer 1; and a value of 1.73 for horizontal anisotropy in both layers. The calibrated model was used to delineate the areal extent of the zone of contribution for wells Cu 969 and Fr 823. Although well Cu 970 is not currently (2004) being used, the areal extent of its zone of contribution also was simulated without additional model calibration. The shape of the areal extent of the zone of contribution was similar for each well and included an area that extended from the well southwest along the Tomstown Formation, and then extended southeast into the metamorphic rocks of South Mountain. The contributing areas from the watersheds of losing streams were also delineated because losing stream reaches bisect the areal extent of the zones of contribution. Spatial uncertainty of the areal extent of the zone of contribution was illustrated using a Monte-Carlo analysis. The model was run 1,000 times using randomly generated parameter sets that were normally distributed within the confidence interval around the optimal values for the three estimated parameters. The model converged and had a reasonable water budget for 980 of the model runs. For each of those 980 model runs, the recharge area was determined, and the results for all runs were compiled and contoured. The results of the Monte-Carlo analysis were compared to the results of the deterministic model, illustrating that the deterministic model has the greatest certainty in the area closest to each well in the Tomstown Formation. The areas farther from the well, upgradient, and in the metamorphic rocks have a higher degree

Pennsylvania↗

USGS2010

Characterization of suspended solids and total phosphorus loadings from small watersheds in Wisconsin

Knowledge of the daily, monthly, and yearly distribution of contaminant loadings and streamflow can be critical for the successful implementation and evaluation of water-quality management practices. Loading data for solids (suspended sediment and total suspended solids) and total phosphorus and streamflow data for 23 watersheds were summarized for four ecoregions of Wisconsin: the Driftless Area Ecoregion, the Northern Lakes and Forests Ecoregion, the North Central Hardwoods Ecoregion, and the Southeastern Wisconsin Till Plains Ecoregion. The Northern Lakes and Forests and the North Central Hardwoods Ecoregions were combined into one region for analysis due to a lack of sufficient data in each region. Urban watersheds, all located in the Southeastern Wisconsin Till Plains, were analyzed separately from rural watersheds as the Rural Southeastern Wisconsin Till Plains region and the Urban Southeastern Wisconsin Till Plains region. Results provide information on the distribution of loadings and streamflow between base flow and stormflow, the timing of loadings and streamflow throughout the year, and information regarding the number of days in which the majority of the annual loading is transported. The average contribution to annual solids loading from stormflow periods for the Driftless Area Ecoregion was 84 percent, the Northern Lakes and Forests/North Central Hardwoods region was 71 percent, the Rural Southeastern Wisconsin Till Plains region was 70 percent, and the Urban Southeastern Wisconsin Till Plains region was 90 percent. The average contributions to annual total phosphorus loading from stormflow periods were 72, 49, 61, and 76 percent for each of the respective regions. The average contributions to annual streamflow from stormflow periods are 20, 23, 31, and 50 percent for each of the respective regions. In all regions, the most substantial loading contributions for solids were in the late winter (February through March), spring (April through May), and early summer (June through July), with fall (October through November) and early winter (December through January) contributing the smallest loadings. The Northern Lakes and Forests/North Central Hardwoods region had some substantial loading in September. There was a similar pattern for total phosphorus loading in all regions, with the pattern somewhat less pronounced in urban watersheds. As with the loading results, average monthly streamflow values were greatest in late winter, spring, and early summer, with the lowest values typically in fall and early winter. Loading contributions were greater from stormflow than from base flow in all instances, except total phosphorus in the Northern Lakes and Forests/North Central Hardwoods region, which had equal or greater base-flow contribution for several months. Base flow constituted a greater percentage of the total streamflow than stormflow in all rural watersheds for all regions. Only a few storms each year dominated the annual loading totals for solids and total phosphorus. When daily loading values were ranked for the year, all regions reached 50 percent of the annual solids loading in the 5 highest loading days and nearly 50 percent of the annual total phosphorus loading in the 14 highest loading days.

Scientific Investigations Report↗

USGS2012

Groundwater monitoring plan for the Missouri River alluvial aquifer in the vicinity of the City of Independence, Missouri, well field

Source contributions to monitoring and supply wells, contributing recharge areas, groundwater travel times, and current (2012) understanding of alluvial water quality were used to develop a groundwater monitoring plan for the Missouri River alluvial aquifer in the vicinity of the City of Independence, Missouri well field. The plan was designed to evaluate long-term alluvial water quality and assess potential changes in, and threats to, well-field water quality. Source contributions were determined from an existing groundwater flow model in conjunction with particle-tracking analysis and verified with water-quality data collected from 1997 through 2010 from a network of 68 monitoring wells. Three conjunctive factors - well-field pumpage, Missouri River discharge, and aquifer recharge - largely determined groundwater flow and, therefore, source contributions. The predominant source of groundwater to most monitoring wells and supply wells is the Missouri River, and this was reflected, to some extent, in alluvial water quality. To provide an estimate of the maximum potential lead time available for remedial action, monitoring wells where groundwater travel times from the contributing recharge areas are less than 2 years and predominately singular sources (such as the Missouri River or the land surface) were selected for annual sampling. The sample interval of the remaining wells, which have varying travel times and intermediate mixtures of river and land-surface contributions, were staggered on a 2-, 3-, or 4-year rotation. This was done to provide data from similar contributing areas and account for inherent aquifer variability yet minimize sample redundancy.

Missouri↗

USGS2014

Water-quality variability and constituent transport and processes in streams of Johnson County, Kansas, using continuous monitoring and regression models, 2003-11

The population of Johnson County, Kansas increased by about 24 percent between 2000 and 2012, making it one of the most rapidly developing areas of Kansas. The U.S. Geological Survey, in cooperation with the Johnson County Stormwater Management Program, began a comprehensive study of Johnson County streams in 2002 to evaluate and monitor changes in stream quality. The purpose of this report is to describe water-quality variability and constituent transport for streams representing the five largest watersheds in Johnson County, Kansas during 2003 through 2011. The watersheds ranged in urban development from 98.3 percent urban (Indian Creek) to 16.7 percent urban (Kill Creek). Water-quality conditions are quantified among the watersheds of similar size (50.1 square miles to 65.7 square miles) using continuous, in-stream measurements, and using regression models developed from continuous and discrete data. These data are used to quantify variability in concentrations and loads during changing streamflow and seasonal conditions, describe differences among sites, and assess water quality relative to water-quality standards and stream management goals. Water quality varied relative to streamflow conditions, urbanization in the upstream watershed, and contributions from wastewater treatment facilities and storm runoff. Generally, as percent impervious surface (a measure of urbanization) increased, streamflow yield increased. Water temperature of Indian Creek, the most urban site which is also downstream from wastewater facility discharges, was higher than the other sites about 50 percent of the time, particularly during winter months. Dissolved oxygen concentrations were less than the Kansas Department of Health and Environment minimum criterion of 5 milligrams per liter about 15 percent of the time at the Indian Creek site. Dissolved oxygen concentrations were less than the criterion about 10 percent of the time at the rural Blue River and Kill Creek sites, and less than 5 percent of the time at the other sites. Low dissolved oxygen at all sites generally coincided with lowest streamflow and warmer water temperatures. Hourly dissolved oxygen concentrations less than 5 milligrams per liter were measured at all sites every year, indicating that even under normal climate conditions in non-urban watersheds such as Kill Creek, dissolved oxygen concentrations may not meet State aquatic-life criterion. Specific conductance was nearly always highest in Indian and Mill Creeks, which were the most urban streams with the largest upstream discharges from wastewater treatment facilities. The largest chloride concentrations and variability were recorded at urban sites and during winter. Each winter during the study period, chloride concentrations in the most urban site, Indian Creek, exceeded the U.S. Environmental Protection Agency-recommended criterion of 230 milligrams per liter for at least 10 consecutive days. The U.S. Environmental Protection Agency-recommended ecoregion criterion for turbidity was exceeded 30 (Indian Creek) to 50 (Blue River) percent of the time. The highest average annual streamflow-weighted suspendedsediment concentration during the study period was in Mill Creek, which has undergone rapid development that likely contributed to higher sediment concentrations. One of the largest suspended-sediment load events in Indian Creek was recorded in early May 2007 when about 25 percent of the total annual sediment load was transported during a period of about 2.25 days. A simultaneous load event was recorded in Kill Creek, when about 75 percent of the total annual sediment load was transported. Sediment yields generally increased as percent impervious surface increased. Computed hourly total nitrogen and total phosphorus concentrations and yields and streamflow-weighted concentrations generally were largest in Indian and Mill Creeks. Annual percent contribution of total nitrogen in the Blue River from wastewater treatment facility discharges ranged from 19 percent in 2010 to 60 percent in 2006. Annual percent contribution of total nitrogen in Indian Creek from wastewater treatment facility discharges ranged from 35 percent in 2010 to 93 percent in 2006. The largest percent nutrient contributions from wastewater discharges coincided with the smallest annual precipitation and streamflow volume, resulting in less contribution originating from runoff. Fecal indicator bacteria Escherichia coli density at the urban Indian Creek site was usually the largest of the five monitoring sites, with an annual median density that consistently exceeded the State primary contact criterion value but was less than the secondary contact criterion. Less than 1 percent of the total annual bacteria load in the Blue River and Indian Creek originated from wastewater discharges, except during 2006 when about 6 percent of the Indian Creek load originated from wastewater. Continuous water-quality monitoring provides a foundation for comprehensive evaluation and understanding of variability and loading characteristics in streams in Johnson County. Because several directly measured parameters are strongly correlated with particular constituents of interest, regression models provide a valuable tool for evaluating variability and loading on the basis of computed continuous data. Continuous data are particularly useful for characterizing nonpoint-source contributions from stormwater runoff. Transmission of continuous data in real-time makes it possible to rapidly detect and respond to potential environmental concerns. As monitoring technologies continue to improve, so does the ability to monitor additional constituents of interest, with smaller measurement error, and at lower operational cost. Continuous water-quality data including model information and computed concentrations and loads during the study period are available at http://nrtwq.usgs.gov/ks/ .

Kansas↗

USGS2002

Sources of metal loads to the Alamosa River and estimation of seasonal and annual metal loads for the Alamosa River basin, Colorado, 1995-97

Metal contamination in the upper Alamosa River Basin has occurred for decades from the Summitville Mine site, from other smaller mines, and from natural, metal-enriched acidic drainage in the basin. In 1995, the need to quantify contamination from various source areas in the basin and to quantify the spatial, seasonal, and annual metal loads in the basin was identified. Data collection occurred from 1995 through 1997 at numerous sites to address data gaps. Metal loads were calculated and the percentages of metal load contributions from tributaries to three risk exposure areas were determined. Additionally, a modified time-interval method was used to estimate seasonal and annual metal loads in the Alamosa River and Wightman Fork. Sources of dissolved and total-recoverable aluminum, copper, iron, and zinc loads were determined for Exposure Areas 3a, 3b, and 3c. Alum Creek is the predominant contributor of aluminum, copper, iron, and zinc loads to Exposure Area 3a. In general, Wightman Fork was the predominant source of metals to Exposure Area 3b, particularly during the snowmelt and summer-flow periods. During the base-flow period, however, aluminum and iron loads from Exposure Area 3a were the dominant source of these metals to Exposure Area 3b. Jasper and Burnt Creeks generally contributed less than 10 percent of the metal loads to Exposure Area 3b. On a few occasions, however, Jasper and Burnt Creeks contributed a substantial percentage of the loads to the Alamosa River. The metal loads calculated for Exposure Area 3c result from upstream sources; the primary upstream sources are Wightman Fork, Alum Creek, and Iron Creek. Tributaries in Exposure Area 3c did not contribute substantially to the metal load in the Alamosa River. In many instances, the percentage of dissolved and/or total-recoverable metal load contribution from a tributary or the combined percentage of metal load contribution was greater than 100 percent of the metal load at the nearest downstream site on the Alamosa River. These data indicate that metal partitioning and metal deposition from the water column to the streambed may be occurring in Exposure Areas 3a, 3b, and 3c. Metals that are deposited to the streambed probably are resuspended and transported downstream during high streamflow periods such as during snowmelt runoff and rainfall runoff. Seasonal and annual dissolved and totalrecoverable aluminum, copper, iron, and zinc loads> for 1995?97 were estimated for Exposure Areas 1, 2, 3a, 3b, and 3c. During 1995?97, many tons of metals were transported annually through each exposure area. Generally, the largest estimated annual totalrecoverable metal mass for most metals was in 1995. The smallest estimated annual total-recoverable metal mass was in 1996, which also had the smallest annual streamflow. In 1995 and 1997, more than 60 percent of the annual total-recoverable metal loads generally was transported through each exposure area during the snowmelt period. A comparison of the estimated storm load at each site to the corresponding annual load indicated that storms contribute less than 2 percent of the annual load at any site and about 5 to 20 percent of the load during the summer-flow period.

Colorado↗

USGS1992

Nonpoint-source pollutant discharges of the three major tributaries to Reelfoot Lake, west Tennessee, October 1987-September 1989

An investigation of the concentration and loads of nitrogen, phosphorus, and suspended sediment in storm runoff to Reelfoot Lake, in western Tennessee, was conducted from October 1987 through September 1989. Concentrations of selected herbicides also were defined. Reelfoot Lake, with a surface area of about 15,500 acres, is the largest natural lake in Tennessee and an important recreation and fisheries resource. Previous studies showed that the lake is hypereutrophic, a condition caused by high concentrations of nutrients in water and sediments discharged from the three principal tributaries (South Reelfoot Creek, North Reelfoot Creek, and Running Slough) to the lake. Pesticides, including herbicides, have been detected in the lake's bottom sediments. Storm runoff contributed about 87percent of the total water discharge of the three main tributaries to Reelfoot Lake. South Reelfoot Creek contributed about 4.7 tons per acre per year of suspended sediment, while North Reelfoot Creek contributed about 1.9 tons per acre per year. Running Slough contributed only about 0.31 ton per acre per year of suspended sediment. Most of the suspended sediment was transported by storm runoff between October and March. About 80 percent of the annual streamflow of the three tributaries occurs during these months. The North Reelfoot Creek basin contributed 8.2 pounds per acre per year of total nitrogen and 2.4 pounds per acre per year of total phosphorus. South Reelfoot Creek basin contributed about 6.5 and 1.3 pounds per acre per year of total nitrogen and phosphorus, respectively, while Running Slough basin contributions were 3.4 and 0.86 pounds per acre per year, respectively. The differences in nutrient yields appear to result from more row-crop agriculture and the relatively steeply sloping agricultural land in the North Reelfoot Creek basin. Ninety-one percent of the total nitrogen load and 95 percent of the total phosphorus load in the three streams was transported by storm runoff. Significant differences in the mean concentrations of nutrients in runoff were defined between the active agricultural months (April through September) and the inactive months (October through March). Storm-runoff samples were analyzed for II selected triazine herbicides. Alachlor and atrazine were the most commonly detected herbicides. Thirty-two percent of the samples contained detectable levels of alachlor and 93 percent of the samples contained detectable levels of atrazine. Ninety percent of the samples collected during the active agricultural months contained detectable leveki of alachlor and all 29 samples contained detectable levels of atrazine. Sixteen samples exceeded lifetime health-advisory levels for atrazine in drinking water (3 micrograms per liter); two samples collected from the April IS, 1988, storm at North Reelfoot Creek and South Reelfoot Creek contained 42 and 57 micrograms per liter of atrazine, respectively. Concentrations of the other nine triazine herbicides were generally less than the level of detection (0.1 microgram per liter).

Tennessee↗

USGS2000

Sources, instream transport, and trends of nitrogen, phosphorus, and sediment in the lower Tennessee River basin, 1980-96

In 1997, the U.S. Geological Survey (USGS) began an assessment of the lower Tennessee River Basin as part of the National Water-Quality Assessment Program. Existing nutrient and sediment data from 1980 to 1996 were compiled, screened, and interpreted to estimate watershed inputs from nutrient sources, provide a general description of the distribution and transport of nutrients and sediments in surface water, and evaluate trends in nutrient and sediment concentrations in the lower Tennessee (LTEN) River Basin. Nitrogen inputs from major sources varied widely among tributary basins in the LTEN River Basin. Point source wastewater discharges contributed between 0 and 0.61 tons per square mile per year [(tons/mi 2 )/yr]. Of the nonpoint sources of nitrogen for which inputs were estimated (atmospheric deposition, nitrogen fixation, fertilizer application, and livestock waste) livestock waste contributed the largest input in about two-thirds (7 out of 11) of the tributary basins, and fertilizer application contributed the largest input in the remaining 4 basins. Nitrogen input from fertilizer application was the most variable spatially among the nonpoint sources of nitrogen, ranging from 1.5 to 23 (tons/mi 2 )/yr. Atmospheric deposition estimates varied the least from basin to basin, ranging from 1.6 to 2.0 (tons/mi 2 )/yr. Estimates of nitrogen input from livestock waste ranged between 2.0 to 13 (tons/mi 2 )/yr. The percentage of the input from each of these nonpoint sources that entered the surface-water system is not known. Wastewater discharge contributed between 0 and 0.14 (ton/mi 2 )/yr of phosphorus to tributary basins. Livestock waste contributed most of the input in 8 out of the 11 basins, and fertilizer application contributed the most in the remaining 3 basins. Estimates of phosphorus input for fertilizer application ranged from 0.35 to 5.1 (tons/mi 2 )/yr and from 0.62 to 4.3 (tons/mi 2 )/yr from livestock waste. Reservoirs on the main stem of the Tennessee River and on the Duck and Elk Rivers affect nutrient transport because hydrodynamic conditions in the reservoirs promote assimilation by aquatic plants and deposition of particulate matter. Observed decreases in total nitrite plus nitrate and dissolved-orthophosphorus concentrations in reservoirs or at sites downstream of reservoirs during summer months were probably related to seasonality of plant growth. Nutrient and sediment data used to estimate annual instream loads and yields were compiled from various water-quality monitoring programs and represent the best available data in the LTEN River Basin, but these data have several characteristics that limit accuracy of load estimates. Many of the monitoring programs were not designed with the objective of annual load estimation, and data representing storm transport are, therefore, sparse; sampling and analytical methods varied through time and among the monitoring programs, hampering spatial and temporal comparisons. The load estimates computed from these data are useful for evaluating broad spatial patterns of instream load, and comparisons of instream load to inputs, but may not be sufficiently accurate for local-scale evaluations of water quality. Estimates of the mean annual instream load of total nitrogen entering (Chattanooga, Tenn.) and leaving (Paducah, Ky.) the LTEN River Basin were 29,000 and 60,000 tons per year (tons/yr), respectively. These estimates represent a gain of 31,000 tons/yr, on average, across the area (18,930 mi 2 ) between these inlet and outlet sites. The sum of the mean annual instream load from gaged tributaries to the main stem within the study unit was 14,000 tons/yr; however, this number cannot be directly compared with the gain between the inlet and outlet sites because (1) the gaged area represents only 30 percent of the total area and (2) the period of record at many tributary sites did not correspond with the period of record at the inlet or outlet sites. Estimates of mean annual instream load of total phosphorus at the inlet and outlet sites of the LTEN River Basin were 1,300 and 5,000 tons/yr, respectively, representing a gain of 3,700 tons/yr, on average, across the study unit. The sum of the gaged tributary load, representing only 28 percent of the area contributing to the main stem, was 4,300 tons/yr. Although this number cannot be closely compared with the gain throughout the study unit, for the same reasons given for total nitrogen, a general comparison suggests that the main stem of the Tennessee River and the tributary embayments along the main stem function as a sink for total phosphorus, removing a substantial amount from the water column through deposition or assimilation. The estimates of inputs can be compared and correlated with yields (area-normalized instream loads); significant correlations between estimates of inputs and yields might be useful as predictive tools for instream water quality where monitoring data are not available. Yields of nitrogen correlated moderately well with inputs from nonpoint sources, based on 1992 estimates. Nitrogen yield was highest [3.5 (tons/mi 2 )/yr] for Town Creek, for which the balance of nonpoint-source inputs to agricultural lands (fertilizer application plus nitrogen fixation plus livestock waste minus harvest) was also the highest [15 (tons/mi 2 )/yr]. Nitrogen yield was low [1.0 (tons/mi 2 )/yr] for the Buffalo River, for which the balance of agricultural nonpoint-source input was correspondingly low [3.2 (tons/mi 2 )/yr, the second lowest]. Correlation of wastewater discharge with yield was poor, and contrasted with the significant correlation between wastewater discharge and median nitrogen concentration during low streamflow. The poor correlation between wastewater discharge and annual yield was expected, however, as wastewater discharge is a small fraction compared with annual yield. In contrast with nitrogen, phosphorus yield did not correlate well with any estimated inputs or land-use types for the tributary basins. Phosphorus yield was highest [1.1 and 0.93 (tons/mi 2 )/yr] at two sites along the Duck River and at Elk River near Prospect [0.89 (ton/mi 2 )/yr]; however, estimates of inputs at these sites were in the middle of their respective ranges. The influence of the outcrop of phosphatic limestone formations of the brown-phosphate districts in the lower Duck and lower Elk River Basins might be responsible for the poor correlation between estimated inputs and yields of phosphorus. The outcrop pattern of these phosphatic limestones are an important factor to consider as regional boundaries are established for attainable, region-specific water-quality criteria for total phosphorus. Estimates of sediment input from cropland soil erosion in 1992 ranged from 51 to 540 (tons/mi 2 )/yr among the major hydrologic units in the LTEN River Basin. Information was not available to estimate this input for individual tributaries. Sediment yield estimates ranged from 65 to 263 (tons/mi 2 )/yr for the three tributary monitoring basins for which instream data were available, and from 17 to 26 (tons/mi 2 )/yr for the Tennessee River at South Pittsburg and at Pickwick Landing Dam, respectively. Lower sediment yields for the main stem sites compared with the tributary sites is probably due to sediment deposition in the main stem of the Tennessee River and tributary embayments along the main stem. Most of the significant trends in nutrient concentrations from about 1985 to about 1995 were decreasing trends, except for total nitrite plus nitrate, which increased at one site on the Elk River. The spatial distribution of decreasing trends of total nitrogen and total ammonia corresponds with the spatial variation among basins in wastewater loading rate. The time period of observed trends corresponds to the period of improvements in municipal treatment, thus decreases in wastewater effluent concentrations of nitrogen might be responsible for the decreasing trend in instream concentrations at these sites. Concentrations of total phosphorus did not decrease during this period at these sites, as might have been expected considering the reductions in wastewater input of phosphorus during this period.

Alabama, Georgia, Kentucky, Mississippi, Tennessee↗

USGS2024

Stream water sourcing from high-elevation snowpack inferred from stable isotopes of water: A novel application of d-excess values

About 80 % of the precipitation at the Colorado River's headwaters is snow, and the resulting snowmelt-driven hydrograph is a crucial water source for about 40 million people. Snowmelt from alpine and subalpine snowpack contributes substantially to groundwater recharge and river flow. However, the dynamics of snowmelt progression are not well understood because observations of the high-elevation snowpack are difficult due to challenging access in complex mountainous terrain as well as the cost and labor intensity of currently available methods. We present a novel approach to infer the processes and dynamics of high-elevation snowmelt contributions predicated upon stable hydrogen and oxygen isotope ratios observed in streamflow. We show that deuterium-excess (d-excess) values of stream water could serve as a comparatively cost-effective proxy for a catchment-integrated signal of high-elevation snowmelt contributions to catchment runoff. We sampled stable hydrogen and oxygen isotope ratios of the precipitation, snowpack, and stream water in the East River, a headwater catchment of the Colorado River, and the stream water of larger catchments at sites on the Gunnison River and Colorado River. The d-excess of snowpack increased with elevation; the upper subalpine and alpine snowpack ( > 3200 m) had substantially higher d-excess compared to lower elevations ( < 3200 m) in the study area. The d-excess values of stream water reflected this because d-excess values increased as the higher-elevation snowpack contributed more to stream water generation later in the snowmelt/runoff season. End-member mixing analyses based on the d-excess data showed that the share of high-elevation snowmelt contributions within the snowmelt hydrograph was on average 44 % and generally increased during melt period progression, up to 70 %. The observed pattern was consistent during 6 years for the East River, and a similar relation was found for the larger catchments on the Gunnison and Colorado rivers. High-elevation snowpack contributions were found to be higher for years with lower snowpack and warmer spring temperatures. Thus, we conclude that the d-excess of stream water is a viable proxy to observe changes in high-elevation snowmelt contributions in catchments at various scales. Inter-catchment comparisons and temporal trends of the d-excess of stream water could therefore serve as a catchment-integrated measure to monitor if mountain systems rely on high-elevation water inputs more during snow drought compared to years of average snowpack depths.

EUGsphere↗

USGS1994

Relationships between 222Rn dissolved in ground water supplies and indoor 222Rn concentrations in some Colorado front range houses

Indoor 222Rn concentrations were measured in 37 houses with alpha track detectors placed in water-use rooms near water sources (bathrooms, laundry rooms, and kitchens) and in non-water-use living rooms, dining rooms, and bedrooms away from water sources. Results show that relative contributions of 222Rn to indoor air from water use are insignificant when soil-gas concentrations are high but become increasingly important as the ratio of 222Rn-in-water:222Rn-in-soil gas increases. High soil-gas 222Rn concentrations may mask 222Rn contributions from water even when waterborne 222Rn concentrations are as high as 750 kBq m-3. Ground water in Precambrian Pikes Peak granite averages 340 kBq m-3222Rn, vs. 170 kBq m-3 in Precambrian migmatite, but average 222Rn concentrations in soil gas are also lower in migmatite. Because the ratio of 222Rn-in- water:222Rn-in-soil gas may be consistently higher for houses in migmatite than in Pikes Peak granite, indoor air in houses built on migmatite may have a greater relative contribution from water use even though average 222Rn concentrations in the water are lower. Continuous monitoring of 222Rn concentrations in air on 15-min intervals also indicates that additions to indoor concentrations from water use are significant and measurable only when soil-gas concentrations are low and concentrations in water are high. When soil-gas concentrations were mitigated to less than 150 Bq m-3 in one house, water contributes 20-40% of the annual indoor 222Rn concentration in the laundry room (222Rn concentration in water of 670 kBq m-3). Conversely, when the mitigation system is inactive, diurnal fluctuations and other variations in the soil-gas 222Rn contribution swamp the variability due to water use in the house. Measurable variations in indoor concentrations from water use were not detected in one house despite a low soil-gas contribution of approximately 150 Bq m-3 because waterborne 222Rn concentrations also are low (80 kBq m-3). This result suggests that 222Rn concentrations in water near the recommended EPA limit in drinking water of 11 kBq m-3 may not contribute measurable amounts of 222Rn to indoor air in most houses.

Health Physics↗

USGS1995

Gross-beta activity in ground water: natural sources and artifacts of sampling and laboratory analysis

Gross-beta activity has been used as an indicator of beta-emitting isotopes in water since at least the early 1950s. Originally designed for detection of radioactive releases from nuclear facilities and weapons tests, analysis of gross-beta activity is widely used in studies of naturally occurring radioactivity in ground water. Analyses of about 800 samples from 5 ground-water regions of the United States provide a basis for evaluating the utility of this measurement. The data suggest that measured gross-beta activities are due to (1) long-lived radionuclides in ground water, and (2) ingrowth of beta-emitting radionuclides during holding times between collection of samples and laboratory measurements. Although 40 K and 228 Ra appear to be the primary sources of beta activity in ground water, the sum of 40 K plus 228 Ra appears to be less than the measured gross-beta activity in most ground-water samples. The difference between the contribution from these radionuclides and gross-beta activity is most pronounced in ground water with gross-beta activities > 10 pCi/L, where these 2 radionuclides account for less than one-half the measured ross-beta activity. One exception is groundwater from the Coastal Plain of New Jersey, where 40 K plus 228 Ra generally contribute most of the gross-beta activity. In contrast, 40 K and 228 Ra generally contribute most of beta activity in ground water with gross-beta activities < 1 pCi/L. The gross-beta technique does not measure all beta activity in ground water. Although 3 H contributes beta activity to some ground water, it is driven from the sample before counting and therefore is not detected by gross-beta measurements. Beta-emitting radionuclides with half-lives shorter than a few days can decay to low values between sampling and counting. Although little is known about concentrations of most short-lived beta-emitting radionuclides in environmental ground water (water unaffected by direct releases from nuclear facilities and weapons tests), their activities are expected to be low. Ingrowth of beta-emitting radionuclides during sample holding times can contribute to gross-beta activity, particularly in ground water with gross-beta activities > 10 pCi/L. Ingrowth of beta-emitting progeny of 238 U, specifically 234 Pa and 234 Th, contributes much of the measured gross-beta activity in ground water from 4 of the 5 areas studied. Consequently, gross-beta activity measurements commonly overestimate the abundance of beta-emitting radionuclides actually present in ground water. Differing sample holding times before analysis lead to differing amounts of ingrowth of the two progeny. Therefore, holding times can affect observed gross-beta measurements, particularly in ground water with 238 U activities that are moderate to high compared with the activity of 40 K plus 228 Ra. Uncertainties associated with counting efficiencies for beta particles with different energies further complicate the interpretation of gross-beta measurements.

Applied Geochemistry↗

USGS2023

Nitrogen isotopes indicate vehicle emissions and biomass burning dominate ambient ammonia across Colorado's Front Range urban corridor

Urban ammonia (NH 3 ) emissions contribute to poor local air quality and can be transported to rural landscapes, impacting sensitive ecosystems. The Colorado Front Range urban corridor encompasses the Denver Metropolitan Area, rural farmland/rangeland and montane forest between the city and the Rocky Mountains. Reactive nitrogen emissions from the corridor are partly responsible for increased N deposition to the wildland-urban interface (WUI) in this region. To determine the significance of individual NH 3 sources to WUI ecosystems, we measured the concentration and isotopic composition (δ 15 N–NH 3 ) of ambient NH 3(g) from April to October 2018 across a five-site urban to rural gradient in the corridor. The urban sites had higher NH 3 concentrations and δ 15 N–NH 3 values than the rural/suburban sites. Based on isotope mixing models, NH 3 emission source contributions for all sites were fertilizer (12 ± 5.7%), livestock waste (18 ± 12%), vehicles (37 ± 23%), and biomass burning (34 ± 20%). Vehicle contributions were consistent across all months with an average of 35% and summer months showed a peak in biomass burning contributions (40%). As wildfires are projected to increase due to climate change, we stress a need for constraints on the isotopic signature of NH 3 emitted from wildfires. Vehicle emissions contributed the greatest amount of NH 3 (40%) at the urban sites while rural/suburban sites had higher agricultural contributions (41%). Had 2018 not had an anomalously high wildfire season, 46% and 60% of the NH 3 would have been attributed to vehicle emissions at the WUI site and urban sites, respectively. NH 3 emissions have historically been ascribed to agricultural activities but these findings illustrate the universal significance of vehicle emissions and the potential for sustained wildfire activity to be a primary contributor to NH 3 . Air quality (e.g., particulate matter) and nitrogen deposition reduction plans may benefit by including management practices that address vehicle NH 3 emissions.

Colorado↗

USGS2020

Monthly suspended-sediment apportionment for a western Lake Erie agricultural tributary

Black Creek, a headwater to the Maumee River and western Lake Erie, is an agricultural basin with a mix of cropland (66%), pasture (19%), and forest (7%) linked by a road network to the rural community. Suspended sediment was collected monthly during the 2018 water year for the main stem and two sub-basins using in-situ, passive samplers that integrated a range of streamflow conditions. Sediment fingerprinting used 44 indicators to apportion samples among five sources: cropland, pasture, forest, road dirt, and streambanks. Cropland, pasture, and streambanks had similar ranges in sediment-bound phosphorus (679-1670 ppm). Cropland contributed 21 ± 15% (monthly mean ± standard deviation; 0-46% among individual months) of suspended sediment during the year. Fall and spring peaks in cropland contribution highlight the ongoing importance of on-field management, but this small contribution of suspended sediment relative to the expanse of cropland may reflect implementation of best-management practices. Pasture contributed 0-66% (16±19%) of suspended-sediment and roads 0-26% (6±6%). Streambanks contributed 12-100% (55±25%) and was the only source identified in all sediment samples. In this basin, most cropland-adjacent streambanks are protected by a riparian setback. However, streams traversing other land-use types are not as consistently protected, and these setbacks do not protect the stream channel from discharge of water from sump pumps, road culverts, or tile drains. The contribution of sediment from other land uses combined with that from the agricultural drainage network (as streambank material) underscores the need to consider water movement in the basin as a whole.

Indiana↗

USGS2006

Precipitation induced stream flow: An event based chemical and isotopic study of a small stream in the Great Plains region of the USA

A small stream in the Great Plains of USA was sampled to understand the streamflow components following intense precipitation and the influence of water storage structures in the drainage basin. Precipitation, stream, ponds, ground-water and soil moisture were sampled for determination of isotopic (D, 18O) and chemical (Cl, SO4) composition before and after two intense rain events. Following the first storm event, flow at the downstream locations was generated primarily through shallow subsurface flow and runoff whereas in the headwaters region - where a pond is located in the stream channel - shallow ground-water and pond outflow contributed to the flow. The distinct isotopic signatures of precipitation and the evaporated pond water allowed separation of the event water from the other sources that contributed to the flow. Similarly, variations in the Cl and SO4 concentrations helped identify the relative contributions of ground-water and soil moisture to the streamflow. The relationship between deuterium excess and Cl or SO4 content reveals that the early contributions from a rain event to streamflow depend upon the antecedent climatic conditions and the position along the stream channel within the watershed. The design of this study, in which data from several locations within a watershed were collected, shows that in small streams changes in relative contributions from ground water and soil moisture complicate hydrograph separation, with surface-water bodies providing additional complexity. It also demonstrates the usefulness of combined chemical and isotopic methods in hydrologic investigations, especially the utility of the deuterium excess parameter in quantifying the relative contributions of various source components to the stream flow. ?? 2006 Elsevier B.V. All rights reserved.

Journal of Hydrology↗

USGS2011

Hydrogeologic settings and groundwater-flow simulations for regional investigations of the transport of anthropogenic and natural contaminants to public-supply wells—Investigations begun in 2004

A study of the Transport of Anthropogenic and Natural Contaminants to public-supply wells (TANC study) was begun in 2001 as part of the U.S. Geological Survey National Water-Quality Assessment (NAWQA) Program. The study was designed to shed light on factors that affect the vulnerability of groundwater and, more specifically, water from public-supply wells to contamination to provide a context for the NAWQA Program's earlier finding of mixtures of contaminants at low concentrations in groundwater near the water table in urban areas across the Nation. The TANC study has included investigations at both the regional (tens to thousands of square kilometers) and local (generally less than 25 square kilometers) scales. At the regional scale, the approach to investigation involves refining conceptual models of groundwater flow in hydrologically distinct settings and then constructing or updating a groundwater-flow model with particle tracking for each setting to help quantify regional water budgets, public-supply well contributing areas (areas contributing recharge to wells and zones of contribution for wells), and traveltimes from recharge areas to selected wells. A great deal of information about each contributing area is captured from the model output, including values for 170 variables that describe physical and (or) geochemical characteristics of the contributing areas. The information is subsequently stored in a relational database. Retrospective water-quality data from monitoring, domestic, and many of the public-supply wells, as well as data from newly collected samples at selected public-supply wells, also are stored in the database and are used with the model output to help discern the more important factors affecting vulnerability in many, if not most, settings. The study began with investigations in seven regional areas, and it benefits from being conducted as part of the NAWQA Program, in which consistent methods are used so that meaningful comparisons can be made. The hydrogeologic settings and regional-scale groundwater-flow models from the initial seven regional areas are documented in Chapter A of this U.S. Geological Survey Professional Paper. Also documented in Chapter A are the methods used to collect and compile the water-quality data, determine contributing areas of the public-supply wells, and characterize the oxidation-reduction (redox) conditions in each setting. A data dictionary for the database that was designed to enable joint storage and access to water-quality data and groundwater-flow model particle-tracking output is included as Appendix 1 of Chapter A. This chapter, Chapter B, documents modifications to the study methods and presents descriptions of two regional areas that were added to the TANC study in 2004.

Professional Paper↗

USGS2004

Determining sources of water and contaminants to wells in a carbonate aquifer near Martinsburg, Blair County, Pennsylvania, by use of geochemical indicators, analysis of anthropogenic contaminants, and simulation of ground-water flow

Water supply for the Borough of Martinsburg, Pa., is from two well fields (Wineland and Hershberger) completed in carbonate-bedrock aquifers in the Morrison Cove Valley. Water supply is plentiful; however, waters with high concentrations of nitrate are a concern. This report describes the sources of water and contaminants to the supply wells. A review of previous investigations was used to establish the aquifer framework and estimate aquifer hydraulic properties. Aquifer framework and simulation of ground-water flow in a 25-square-mile area using the MODFLOW model helped to further constrain aquifer hydraulic properties and identify water-source areas in the zone of contribution of ground water to the well fields. Flow simulation identified potential contaminant-source areas. Data on contaminants and geochemical characteristics of ground water at the well fields were compared to the results of flow simulation. The Woodbury Anticline controls the aquifer framework near the well fields and four carbonate-bedrock formations contain the primary aquifers. Three carbonate-bedrock aquifers of Ordovician age overlie the Gatesburg aquifer of Cambrian age on the flanks of the anticline. Fracture, not conduit, permeability was determined to be the dominant water-bearing characteristic of the bedrock. The horizontal hydraulic conductivity of the Gatesburg aquifer is about 36 feet per day. The other carbonate aquifers (Nittany/Stonehenge, Bellefonte/Axemann, and Coburn through Loysburg aquifers) overlying and flanking the Gatesburg aquifer have horizontal hydraulic conductivities of about 1 foot per day. Regional directions of ground-water flow are toward the major streams with Clover Creek as the major discharge point for ground water in the east. Ground-water flow to the well fields is anisotropic with a 5:1 preferential horizontal direction along strike of the axial fold of the anticline. Thus, the zone of contribution of ground water to the well fields is elongate in a north-south direction along the anticline axis, with the majority of the flow to the well fields originating from the south. Human activity in the areal extent of the zone of contribution to the well fields was the source of contaminants. The areal extent of the zone of contribution included both urban areas in the Borough and a large amount of agricultural land. By relating results of flow simulation, natural geochemistry, and analyses of anthropogenic (human-made) contaminants, the source areas for water and contaminants were determined with more confidence than by using only flow simulation. Analysis of natural geochemistry identified water sources from both limestone and dolomite aquifers. Geochemistry results also indicated fractures, not conduits, were the dominant source of water from aquifers; however, quantitative source identification was not possible. Chemical ratios of chloride and bromide were useful to show that all samples of ground water had sources with chemical contributions from land surface. Nitrogen isotope ratio analysis indicated animal manure as the possible primary source of nitrate in most ground water. Some of the nitrate in ground water had chemical fertilizer as a source. At the Wineland well field, chemical fertilizer was likely the source of nitrate. The nitrate in water from the Hershberger well field was from a mixture of fertilizer and animal-manure sources. Human sewage was ruled out as a major source of nitrate in water from the municipal wells by results showing 1) wastewater compounds in sewage were rarely detected and 2) a mass-balance calculation indicating the small contribution of nitrogen that could be attributed to septic systems.

Scientific Investigations Report↗

USGS2006

Occurrence of organic wastewater compounds in drinking water, wastewater effluent, and the Big Sioux River in or near Sioux Falls, South Dakota, 2001-2004

The U.S. Geological Survey (USGS) in cooperation with the city of Sioux Falls conducted several rounds of sampling to determine the occurrence of organic wastewater compounds (OWCs) in the city of Sioux Falls drinking water and waste-water effluent, and the Big Sioux River in or near Sioux Falls during August 2001 through May 2004. Water samples were collected during both base-flow and storm-runoff conditions. Water samples were collected at 8 sites, which included 4 sites upstream from the wastewater treatment plant (WWTP) discharge, 2 sites downstream from the WWTP discharge, 1 finished drinking-water site, and 1 WWTP effluent (WWE) site. A total of 125 different OWCs were analyzed for in this study using five different analytical methods. Analyses for OWCs were performed at USGS laboratories that are developing and/or refining small-concentration (less than 1 microgram per liter (ug/L)) analytical methods. The OWCs were classified into six compound classes: human pharmaceutical compounds (HPCs); human and veterinary antibiotic compounds (HVACs); major agricultural herbicides (MAHs); household, industrial,and minor agricultural compounds (HIACs); polyaromatic hydrocarbons (PAHs); and sterol compounds (SCs). Some of the compounds in the HPC, MAH, HIAC, and PAH classes are suspected of being endocrine-disrupting compounds (EDCs). Of the 125 different OWCs analyzed for in this study, 81 OWCs had one or more detections in environmental samples reported by the laboratories, and of those 81 OWCs, 63 had acceptable analytical method performance, were detected at concentrations greater than the study reporting levels, and were included in analyses and discussion related to occurrence of OWCs in drinking water, wastewater effluent, and the Big Sioux River. OWCs in all compound classes were detected in water samples from sampling sites in the Sioux Falls area. For the five sampling periods when samples were collected from the Sioux Falls finished drinking water, only one OWC was detected at a concentration greater than the study reporting level (metolachlor; 0.0040 ug/L). During base-flow conditions, Big Sioux River sites upstream from the WWTP discharge had OWC contributions that primarily were from nonpoint animal or crop agriculture sources or had OWC concentrations that were minimal. The influence of the WWTP discharge on OWCs at downstream river sites during base-flow conditions ranged from minimal influence to substantial influence depending on the sampling period. During runoff conditions, OWCs at sites upstream from the WWTP discharge probably were primarily contributed by nonpoint animal and/or crop agriculture sources and possibly by stormwater runoff from nearby roads. OWCs at sites downstream from the WWTP discharge probably were contributed by sources other than the WWTP effluent discharge, such as stormwater runoff from urban and/or agriculture areas and/or resuspension of OWCs adsorbed to sediment deposited in the Big Sioux River. OWC loads generally were substantially smaller for upstream sites than downstream sites during both base-flow and runoff conditions.discharge had OWC contributions that primarily were from nonpoint animal or crop agriculture sources or had OWC concentrations that were minimal. The influence of the WWTP discharge on OWCs at downstream river sites during base-flow conditions ranged from minimal influence to substantial influence depending on the sampling period. During runoff conditions, OWCs at sites upstream from the WWTP discharge probably were primarily contributed by nonpoint animal and/or crop agriculture sources and possibly by stormwater runoff from nearby roads. OWCs at sites downstream from the WWTP discharge probably were contributed by sources other than the WWTP effluent discharge, such as stormwater runoff from urban and/or agriculture areas and/or resuspension of OWCs adsorbed to sediment deposited in the Big Sioux River. OWC loads generally were substantially smaller for

South Dakota↗