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At least 1,117 records · Page 62Linked to original sources
USGS2026

Estimating aftershock risk for entry into earthquake-damaged buildings

We present a simple method to estimate the risk of experiencing strong shaking from aftershocks during entry into earthquake-damaged buildings. We compute wait times until the probability of strong ground shaking from aftershocks reaches a predefined risk threshold; for example, a 0.4 percent probability of experiencing Modified Mercalli Intensity 7 or greater shaking during the planned building entry. We also develop a relation between aftershock probability and the probability of strong shaking, so that users can reference the U.S. Geological Survey aftershock forecast during an ongoing aftershock sequence to determine if the risk threshold has been met. We apply our method to active continental regions (for example, the Western United States), stable continental regions (for example, the Central and Eastern United States), and subduction zones (for example, Cascadia or Alaska).

Open-File Report↗
USGS1978

A computer program for simulating salinity loads in streams

A FORTRAN IV program that simulates salinity loads in streams is described. Daily values of stream-discharge in cubic feet per second, or stream-discharge and specific conductance in micromhos, are used to estimate daily loads in tons by one of five available methods. The loads are then summarized by computing either total and mean monthly loads or various statistics for each calendar day. Results are output in tabular and, if requested, punch card format. Under selection of appropriate methods for estimating and summarizing daily loads is provided through the coding of program control cards. The program is designed to interface directly with data retrieved from the U.S. Geological Survey WATSTORE Daily Values File. (Woodard-USGS)

Open-File Report↗
USGS1996

Determination of roughness coefficients for streams in west-central Florida

Physical and hydraulic characteristics are presented for 10 west-central Florida stream reaches. These may be used as reference reaches for estimating Manning's roughness coefficient, n, in similar rivers and channels. Discharge in these reaches ranged from 1.8 to 3,010 cubic feet per second and water-surface slope ranged from 0.00002 to 0.00476 foot per foot. Sites were selected at or near U.S. Geological Survey streamflow gaging stations at which the stage-discharge relations were relatively stable. Crest-stage gages were installed at appropriate locations in each study reach in order to obtain water-surface elevations. Water-surface profiles were collected over a range of discharges at each of the 10 sites and the roughness coefficient was computed for each discharge. For the 104 recorded streamflow events used in this report, the computed roughness coefficients ranged from 0.021 to 0.218 and the mean was 0.072 . The median n value was 0.060; 70 percent of the time the n value was greater than 0.047 and 80 percent of the time the computed n was greater than 0.043. Bed material is so uniform at sites throughout west-central Florida that there is negligible variation in roughness as a result of variation in bed material. Streambank vegetation appears to be the major contributor to variations in roughness values for streams in west-central Florida. Channel roughness can be estimated quantitatively by evaluating the interaction of all roughness factors. Photographs of sites where n values have been computed can be used for comparison to estimate values at similar sites. Using a base n value of 0.040 and increasing n for factors of vegetation, channel obstructions, and other factors provides the best determination of n values for streams in west-central Florida.

Open-File Report↗
USGS1972

Mars chart, MC-10 (uncontrolled photomosaic)

This mosaic was made with unrectified Mariner 9 computer enhanced pictures (vertical automatic gain control version) scaled for a "best fit" based on spacecraft tracking data. Discrepancies between image positions are as large as one degree in latitude and one degree in longitude.

Open-File Report↗
USGS2024

Water-quality constituent concentrations and loads computed using real-time water-quality data for the Republican River, Clay Center, Kansas, August 2018 through July 2023

Milford Lake, the largest reservoir by surface area in Kansas, has had confirmed harmful algal blooms every summer since reporting began in 2011, except 2018–19. Milford Lake has been listed as impaired and designated hypereutrophic under section 303(d) of the 1972 Clean Water Act. In 2014, the Kansas Department of Health and Environment established a total maximum daily load for eutrophication and dissolved oxygen impairments. In 2018, the Natural Resources Conservation Service funded the Regional Conservation Partnership Program for the Milford Lake Watershed to focus on best management practices in the Lower Republican River Basin. The U.S. Geological Survey, in cooperation with the Kansas Water Office, completed this study to assess and quantify water-quality constituent concentrations and loads for total nitrogen (TN), total phosphorus (TP), and suspended sediment (SS) using previously published models for the Republican River near Clay Center, Kansas (U.S. Geological Survey station 06856600), about 15 miles upstream from Milford Lake, during August 1, 2018, through July 31, 2023. TN, TP, and SS concentrations and loads were monitored because of their relation to water supply and water-quality issues in Milford Lake, including nutrient and sediment transport, taste-and-odor events, potentially toxic cyano-harmful algal bloom events, and subsequent downstream transport of contaminants. Data from this report can be used to evaluate changing conditions, provide science-based information for decision making, and help meet regulatory requirements. The study mean annual loads for TN and TP were greater than the reported mean annual total maximum daily load and exceeded the watershed reduction goals as well as Kansas nonpoint source reduction goals defined by the Watershed Restoration and Protection Strategy for the Lower Republican watershed. TN and TP annual loads during 2019–20 were greater than the defined mean annual total maximum daily load. During 2022, TN and TP annual loads were less than the Kansas nonpoint source reduction goal and during 2023 were less than the watershed reduction goal. SS loads were less than the mean annual sedimentation rate computed from the total maximum daily load for the entirety of the study period, and the study mean annual load was 72 percent less than the designed annual reservoir sedimentation rate for Milford Lake. Data collected during the study period represented a wide range of streamflow and water-quality conditions at the Clay Center site, ranging from low-flow with less frequent runoff during 2023 to high-flow with frequent runoff during 2018. Nutrient reduction goals were only met in the final 2 years of the study period when annual mean flow conditions were lower than normal, indicating that goals may be unattainable during average or high-flow conditions. In all years except 2019, the annual mean SS load was less than the 20-year sediment load reduction target. Although annual SS loads at the Clay Center site generally decreased over time, corresponding reductions in annual streamflow indicated that these reductions may primarily be related to less frequent runoff from the upstream basin. Continued water-quality monitoring and tracking of best management practices are necessary to understand the success of Regional Conservation Partnership Program efforts to reduce nutrient transport in the Milford Lake Watershed.

Kansas↗
USGS2020

Modified GIC estimation using 3-D Earth conductivity

Geomagnetically induced currents (GICs) are quasi-direct current (DC) electric currents that flow in technological conductors during geomagnetic storms. Extreme GICs are hazardous to man-made infrastructure. GICs enter and exit the technological systems, such as the electric power grid, at grounding points, and their magnitudes depend on the currents that flow underground. They are, therefore, a function of the Earth's electrical conductivity, represented at ground level as Earth impedances, as well as the resistance parameters of the power network. Traditional GIC estimation practices are based on Earth impedances obtained from laterally homogeneous or piecewise layered-Earth models. We refer to these methods, collectively, as the 1-D approximation. However, GIC hazard mitigation can be improved with more accurate GIC modeling that takes the spatially heterogeneous Earth's conductivity into account. Here, we propose a modified approximation for GIC estimation that is very similar to the 1-D approximation but is instead derived from empirical 3-D Earth impedances. Our formulation sets up the computation of static, frequency-dependent power line telluric response functions, which, once computed, may be considered part of the power grid system model. These response functions may then be used for historical scenario analysis of GIC hazards and for simplified real-time, albeit approximate, GIC estimation in a power grid. This modest modification to the simpler local field formulation approach avoids real-time integration of geoelectric fields along power lines while taking the realistic 3-D Earth into account in a rigorous manner. Once implemented, the method provides a power grid operator with the benefits of convenience and computational speed for a first look real-time operational GIC hazard assessment. We estimate that the proposed modified 3-D GIC modeling approach produces GIC values that are well within 50% of those obtained with the full-scale power line integration of spatially variable geoelectric fields, for storms comparable in scale to the 2003 Halloween storm, all geological structures, and power lines located in the contiguous United States and other low- to middle-latitude regions.

Space Weather↗
USGS2021

Evaporation from Lake Mead and Lake Mohave, Nevada and Arizona, 2010–2019

Evaporation-rate estimates at Lake Mead and Lake Mohave, Nevada and Arizona, were based on eddy covariance and available energy measurements from March 2010 through April 2019 at Lake Mead and May 2013 through April 2019 at Lake Mohave. The continuous data needed to compute monthly evaporation were collected from floating-platform and land-based measurement stations located at each reservoir. Collected data include latent- and sensible-heat fluxes, net radiation, air temperature, wind speed, humidity, and water-temperature profiles. Data collection, analysis methods, and monthly evaporation results for Lake Mead through February 2012 were documented in a U.S. Geological Survey (USGS) Scientific-Investigations Report, 2013–5229. Monthly evaporation and associated datasets for both reservoirs through April 2015 were published in a USGS Data Release (https://doi.org/10.5066/F79C6VG3). Average annual evaporation at Lake Mead was 1,896 millimeters (mm), which is a 10 percent difference from the 1,718 mm average annual evaporation at Lake Mohave; this was primarily due to differences in available energy. Average annual available energy at Lake Mead was 139 watts per square meter (W/m 2 ), which is an 18 percent difference from the 116 W/m 2 average annual available energy at Lake Mohave. Differences in available energy are driven by differences in advected heat between Lake Mead and Lake Mohave; advected heat at Lake Mohave is lower due to colder inflows and warmer outflows. Lake Mead monthly evaporation estimates for this study compare reasonably well to the Bureau of Reclamation’s 24-Month Study (24MS) evaporation coefficients, which are based on pioneering studies from the 1950s. Temporal trends in this study indicate that the effects of heat storage at Lake Mead were underestimated in the 24MS, particularly during the fall months when energy was released from the lake. Mean monthly evaporation rates at Lake Mead were greater than Lake Mohave from June through November during the study period. The seasonal pattern of evaporation at Lake Mohave in this study indicates that the effects of available energy were underestimated in the 24MS coefficients for this reservoir, and that evaporation was substantially overestimated from spring through summer during the study period of 2013 through 2019.

Arizona, Nevada↗
USGS2009

Hydrogeology and Simulation of Groundwater Flow in the Plymouth-Carver-Kingston-Duxbury Aquifer System, Southeastern Massachusetts

The glacial sediments that underlie the Plymouth-Carver-Kingston-Duxbury area of southeastern Massachusetts compose an important aquifer system that is the primary source of water for a region undergoing rapid development. Population increases and land-use changes in this area has led to two primary environmental effects that relate directly to groundwater resources: (1) increases in pumping that can adversely affect environmentally sensitive groundwater-fed surface waters, such as ponds, streams, and wetlands; and (2) adverse effects of land use on the quality of water in the aquifer. In response to these concerns, the U.S. Geological Survey, in cooperation with the Massachusetts Department of Environmental Protection, began an investigation in 2005 to improve the understanding of the hydrogeology in the area and to assess the effects of changing pumping and recharge conditions on groundwater flow in the Plymouth-Carver-Kingston-Duxbury aquifer system. A numerical flow model was developed based on the USGS computer program MODFLOW-2000 to assist in the analysis of groundwater flow. Model simulations were used to determine water budgets, flow directions, and the sources of water to pumping wells, ponds, streams, and coastal areas. Model-calculated water budgets indicate that approximately 298 million gallons per day (Mgal/d) of water recharges the Plymouth-Carver-Kingston-Duxbury aquifer system. Most of this water (about 70 percent) moves through the aquifer, discharges to streams, and then reaches the coast as surface-water discharge. Of the remaining 30 percent of flow, about 25 percent of the water that enters the aquifer as recharge discharges directly to coastal areas and 5 percent discharges to pumping wells. Groundwater withdrawals are anticipated to increase from the current (2005) rate of about 14 Mgal/d to about 21 Mgal/d by 2030. Pumping from large-capacity production wells decreases water levels and increases the potential for effects on surface-water bodies, which are affected by pumping and wastewater disposal locations and rates. Pumping wells that are upgradient of surface-water bodies potentially capture water that would otherwise discharge to these surface-water bodies, thereby reducing streamflow and pond levels. The areas most affected by proposed increases in groundwater withdrawals are in the Towns of Plymouth and Wareham where more than half of the proposed increase in pumping will occur. In response to an increase of about 7 Mgal/d of pumping, groundwater discharge to streams is reduced by about 6 cubic feet per second (ft3/s) (about 4 Mgal/d) from a total of about 325 ft3/s. Reduction in streamflow is moderated by an increase of artificial recharge from wastewater returned to the aquifer by onsite domestic septic systems and centralized wastewater treatment facilities. It is anticipated that about 3 Mgal/d of the 7 Mgal/d of increase in pumped water will be returned to the aquifer as wastewater by 2030. Currently (2005) about 3 percent of groundwater discharge to streams is from wastewater return flow to the aquifer during average conditions. During drought conditions, the component of streamflow augmented by wastewater return flow doubles as wastewater recharge remains constant and aquifer recharge rates decrease. Wastewater return flow, whether as direct groundwater discharge to streams or as an additional source of aquifer recharge, increases the height of the water table near streams, thereby moderating the effects of increased groundwater withdrawals on streamflow. An analysis of a simulated drought similar to the 1960s drought of record indicates that the presence of streams moderates the effects on water levels of reduced aquifer recharge. The area where water-table altitudes were least affected by drought was in the Weweantic River watershed in the Town of Carver. Water levels decreased by less than 2 feet from current average conditions compared to decreases of greater than 5

Scientific Investigations Report↗
USGS2000

Digital orthophoto quadrangles

A digital orthophoto quadrangle (DOQ) is a computer-generated image of an aerial photograph in which image displacement caused by terrain relief and camera tilts has been removed. It combines the image characteristics of a photograph with the geometric qualities of a map.

Fact Sheet↗
USGS2012

GloVis

The Global Visualization Viewer (GloVis) trifold provides basic information for online access to a subset of satellite and aerial photography collections from the U.S. Geological Survey Earth Resources Observation and Science (EROS) Center archive. The GloVis (http://glovis.usgs.gov/) browser-based utility allows users to search and download National Aerial Photography Program (NAPP), National High Altitude Photography (NHAP), Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), Earth Observing-1 (EO-1), Global Land Survey, Moderate Resolution Imaging Spectroradiometer (MODIS), and TerraLook data. Minimum computer system requirements and customer service contact information also are included in the brochure.

General Information Product↗
USGS2006

Hydraulic and geomorphic monitoring of experimental bridge scour mitigation at selected bridges in Utah, 2003-05

Unique bridge scour mitigation designs using concrete A-Jacks were developed by the Utah Department of Transportation and installed at the Colorado River Bridge at State Road 191 and the Green River Bridge at State Road 19. The U.S. Geological Survey monitored stream reaches at these sites by collecting streambed-topography and water-velocity data from 2003 through 2005. These data were acquired annually from a moving boat with an acoustic Doppler current profiler and a differential global positioning system. Raw unordered data were processed and readied for interpolation into organized datasets with DopplerMacros, a set of computer programs. Processed streambed topography data were geostatistically interpolated by using Ordinary Kriging, and inverse distance weighting interpolation was used in the development of the two-dimensional velocity datasets. These organized datasets of topography and velocity were developed for each survey of the two bridge sites. A comparison of the riverbed topography data for each survey was done. An increase in bed elevation related to the installation of the A-Jacks scour countermeasures is evident at the Colorado River Bridge at State Road 191. The three topographic datasets acquired after the installation at the Green River Bridge at State Road 19 show few changes.

Utah↗
USGS2015

Simulation of the regional groundwater-flow system of the Menominee Indian Reservation, Wisconsin

A regional, two-dimensional, steady-state groundwater-flow model was developed to simulate the groundwater-flow system and groundwater/surface-water interactions within the Menominee Indian Reservation. The model was developed by the U.S. Geological Survey (USGS), in cooperation with the Menominee Indian Tribe of Wisconsin, to contribute to the fundamental understanding of the region’s hydrogeology. The objectives of the regional model were to improve understanding of the groundwater-flow system, including groundwater/surface-water interactions, and to develop a tool suitable for evaluating the effects of potential regional water-management programs. The computer code GFLOW was used because of the ease with which the model can simulate groundwater/surface-water interactions, provide a framework for simulating regional groundwater-flow systems, and be refined in a stepwise fashion to incorporate new data and simulate groundwater-flow patterns at multiple scales. Simulations made with the regional model reproduce groundwater levels and stream base flows representative of recent conditions (1970–2013) and illustrate groundwater-flow patterns with maps of (1) the simulated water table and groundwater-flow directions, (2) probabilistic areas contributing recharge to high-capacity pumped wells, and (3) estimation of the extent of infiltrated wastewater from treatment lagoons. The groundwater-flow model described in this report simulates the major hydrogeologic features of the modeled area, including surficial unconsolidated aquifers, groundwater/surface-water interactions, and groundwater withdrawals from existing high-capacity production wells. Areas contributing recharge to pumped high-capacity wells on the Menominee Indian Reservation were delineated by tracking simulated water particles from the water table to wells in combination with Monte Carlo techniques, and maps of the probability of capture for each well nest were produced. Groundwater-agebased areas contributing recharge to wells were simulated by using the calibrated set of parameters and porosity values adjusted to account for bias in simulated saturated thickness. Simulations were performed for current (2013) pumping rates. The simulations show a range in sensitivity of the simulated areas contributing recharge to wells given the parameters evaluated through the Monte Carlo analysis. The areas contributing recharge to supply wells for the villages of Zoar and Neopit are long and narrow, with a sharp gradation from high to low probability of capture. The areas contributing recharge to supply wells for Middle Village and the village of Keshena exhibit a sharp gradation from high to low probability over a relatively small area between the well and a local groundwater mound. The highest probability areas contributing recharge to the supply wells for the Villages of Onekewat and Redwing are in the immediate vicinity of the wells. These wells also have an extensive area with low probability for capturing water that is likely due to a locally low hydraulic gradient and the large degree of uncertainty associated with the lakebed resistance parameters that control interaction between groundwater and local lakes. Additional field investigations and associated local model refinements would facilitate further reductions in uncertainty associated with simulated areas contributing recharge to the wells. The likely extent of the Neopit wastewater plume was simulated by using the groundwater-flow model and Monte Carlo techniques to evaluate the sensitivity of predictive simulations to a range of model parameter values. Wastewater infiltrated from the currently operating lagoons flows predominantly south toward Tourtillotte Creek. Some of the infiltrated wastewater is simulated as having a low probability of flowing beneath Tourtillotte Creek to the nearby West Branch Wolf River. Results for the probable extent of the wastewater plume are considered to be qualitative because the method only considers advective flow and does not account for processes affecting contaminant transport in porous media. Therefore, results for the probable extent of the wastewater plume are sensitive to the number of particles used to represent flow from the lagoon and the resolution of a synthetic grid used for the analysis. Nonetheless, it is expected that the qualitative results may be of use for identifying potential downgradient areas of concern that can then be evaluated using the quantitative “area contributing recharge to wells” method or traditional contaminant-transport simulations.

Wisconsin↗
USGS2015

Water quality of the Little Arkansas River and Equus Beds Aquifer before and concurrent with large-scale artificial recharge, south-central Kansas, 1995-2012

The city of Wichita artificially recharged about 1 billion gallons of water into the Equus Beds aquifer during 2007–2012 as part of Phase I recharge of the Artificial Storage and Recovery project. This report, prepared in cooperation by the U.S. Geological Survey and the city of Wichita, Kansas, summarizes Little Arkansas River (source-water for artificial recharge) and Equus Beds aquifer water quality before (1995–2006) and during (2007–2012) Artificial Storage and Recovery Phase I recharge. Additionally, aquifer water-quality distribution maps are presented and water-quality changes associated with Phase I recharge timing are described. Computed chloride concentrations in the Little Arkansas River exceeded the Federal secondary maximum contaminant level (SMCL) about 20 percent of the time during 1999 through 2012, primarily during low-flow conditions. Groundwater chloride concentrations during 2001 through 2012 exceeded the SMCL in about 6 percent of shallow wells and 7 percent of deep wells, primarily near Burrton, Kansas and along the Arkansas River. Nearly all surface water nitrate plus nitrite concentrations during 1995 through 2012 were less than the Federal maximum contaminant level (MCL); groundwater nitrate plus nitrite concentrations exceeded the MCL in about 16 percent of shallow groundwater samples and were minimal in the deeper parts of the aquifer. Several trace elements frequently exceeded drinking water criteria, including arsenic, iron, and manganese. Recharge activities at Phase I recharge wells have not resulted in substantial effects on groundwater quality in the area, likely because the total amount of water recharged is relatively small (1 billion gallons) compared to aquifer storage volume (greater than 990 billion gallons in winter 2012). The eastward movement of the Burrton chloride plume is likely being slowed by a line of recharge locations associated with Phase I; however, chloride concentrations in deep groundwater still advanced to less than one half mile from the central part of the study area. Water-quality constituents of concern (major ions, nutrients, trace elements, triazine herbicides, and fecal indicator bacteria) have not increased substantially and are likely more affected by climatological (natural recharge by precipitation) and natural (geochemical oxidation/reduction, metabolic and decay rates) processes than artificial recharge. Arsenic remains a water-quality constituent of concern because of natural and continued persistence of concentrations exceeding the Federal maximum contaminant level of 10 micrograms per liter, especially in the deeper parts of the Equus Beds aquifer.

Kansas↗
USGS1976

Hydrologic evaluation of salinity control and reclamation projects in the Indus Plain, Pakistan--A summary

This report summarizes the observations and findings of a team of four specialists from the U.S. Geological Survey assigned to Pakistan under the auspices of the U.S. Agency for International Development during May to August 1972 for a hydrologic evaluation of Salinity Control and Reclamation Projects in the Indus Plain Individual members of the team undertook comprehensive studies related to climatology, surface-water hydrology, and the canal system; streamflow and sediment yields of the rivers; computer applications to hydrologic data; aquifer characteristics; hydrologic evaluation of Salinity Control and Reclamation Projects (SCARPs); tubewell performance; hydrology of shallow versus deep tubewells; well and well-screen design in the Indus Plain; evaluation of observed and anticipated trends in both private and public tubewell development; evaluation of water-quality programs, data analysis, and records, and computer coding of special water-quality data; and evaluation of water-level data, well discharge and specific-capacity tests and aquifer tests. The reclamation program, by pumping from tubewells, has been notably successful in lowering the water table, in providing supplemental water for irrigation and for leaching of salinized soils, and in improving crop production. Some changes in water quality have been observed in SCARP-I and the Mona Scheme of SCARP-II, but these have not as yet (1972) significantly affected the utility of the water for irrigation. Problems associated with reclamation include control of deterioration in performance of tubewells and their rehabilitation, local brackish or saline-water encroachment, and maintenance of a favorable salt balance in the ground-water system. Rapid and as yet (1972) unregulated growth of shallow private tubewell development in the past decade has introduced complicating factors to the reclamation planning of the early 1960's which had emphasized public tubewell development through the SCARP program. In comparing shallow (0-200 feet) with deep (200-400 feet} tubewell development, it is concluded that long-term response of the water table is the same, whether many shallow wells of small capacity or fewer deeper wells of large capacity pump the same total volume of water in the same area. Moreover, it is concluded that there is no definite advantage for either type of pumping regime with respect to water quality. Utilization of the Punjab aquifer could be greatly enhanced by recharge of high-quality water diverted from the Chenab and Jhelum Rivers to the Ravi and Sutlej Rivers by way of the link and irrigation canals during periods of surplus flow. Recharge to the aquifer could also be improved by diversion of high-quality water from the Chenab and the Jhelum to natural nalas and other surface drainageways during periods of surplus flow. Such recharge would be of much better quality than water leaching downward from irrigated fields. Continued monitoring of the hydrologic system and research on problems engendered by reclamation are essential to the viability of the SCARP program and related water-resources development in the Indus River Basin.

Water Supply Paper↗
USGS2015

Particle tracking for selected groundwater wells in the lower Yakima River Basin, Washington

The Yakima River Basin in south-central Washington has a long history of irrigated agriculture and a more recent history of large-scale livestock operations, both of which may contribute nutrients to the groundwater system. Nitrate concentrations in water samples from shallow groundwater wells in the lower Yakima River Basin exceeded the U.S. Environmental Protection Agency drinking-water standard, generating concerns that current applications of fertilizer and animal waste may be exceeding the rate at which plants can uptake nutrients, and thus contributing to groundwater contamination. The U.S. Geological Survey (USGS) recently completed a regional scale transient three-dimensional groundwater-flow model of the Yakima River Basin using MODFLOW-2000. The model was used with the USGS particle-tracking code MODPATH to generate advective flowpaths and associated travel times. Analyses used particle backtracking in time from September 2001 through 504 monthly stress periods to October 1959 or until pathlines terminated at a model boundary. The particle starting locations were assigned to 1,000 foot square computational model cells containing one or more of the 121 sampling locations with measured nitrate concentrations greater than the U.S. Environmental Protection Agency drinking-water standard for nitrate (10 milligrams per liter [mg/L]). Of the 2,403 particles, the simulated pathlines for 2,080 reached the water table within the 42-year simulation period, thus identifying the predicted recharge areas for those particles. The median horizontal straight-line distance was 13,194 feet between starting and ending locations for these particles and the median time-of-travel for particles that intersected the water table was 984 days. Well to water-table travel times for 75.4 percent of the particles were less than the average travel time of 3,749 days. Predicted recharge locations for all particles, including those that did not reach the water table in 42 years, were between 50 feet and 34 miles horizontal distance from their starting locations, with a median distance of less than 3 miles away. Generalized groundwater-flow directions in unconsolidated basin-fill deposits were towards the Yakima River, which acts as a local sink for shallow groundwater, and roughly parallel to topographic gradients. Particles backtracked from more shallow aquifer locations traveled shorter distances before reaching the water table than particles from deeper locations. Flowpaths for particles starting at wells completed in the basalt units underlying the basin-fill deposits sometimes were different than for wells with similar lateral locations but more shallow depths. In cases where backtracking particles reached geologic structures simulated as flow barriers, abrupt changes in direction in some particle pathlines suggest significant changes in simulated hydraulic gradients that may not accurately reflect actual conditions. Most groundwater wells sampled had associated zones of contribution within the Toppenish/Benton subbasin between the well and the nearest subbasin margin, but interpretation of these results for any specific well is likely to be complicated by the assumptions and simplifications inherent in the model construction process. Delineated zones of contribution for individual wells are sensitive to the depths assigned to the screened interval of the well, resulting in simulated areal extents of the zones of contribution to a discharging well that are elongated in the direction of groundwater flow.

Washington↗
USGS1997

Trends in nutrient concentration and load for streams in the Mississippi River Basin, 1974-94

Trends in nutrient concentration and load are computed for 40 stations on 24 streams in the Mississippi River Basin. The drainage area of the Mississippi Basin covers about 42 percent of the conterminous United States, and the Mississippi River discharges about 420 billion gallons per day of freshwater to the Gulf of Mexico. The period for which trends are analyzed varies for each station but generally comprises water years 1974–94. Stations included in this analysis are part of the National Stream Quality Accounting Network operated by the U.S. Geological Survey. LOWESS (LOcally WEighted Scatterplot Smoothing) smooth lines superimposed on graphs of flow-adjusted residuals of concentration versus time and load versus time indicate short-term trends for each station. Kendall-Theil robust lines superimposed on the same graphs indicate long-term trends. Long-term trends were evaluated using the slope of the Kendall-Theil robust line and Kendall’s tau. Annual loads are estimated with regression analysis and corrected for log-transformation bias with the MVUE (Minimum Variance Unbiased Estimator). Trends in annual streamflow are presented to aid in the interpretation of nutrient trends. Statistically significant long-term increases in flow-adjusted residual concentrations of total nitrogen were detected at 14 stations, decreases were detected at 6 stations, and no significant trends were detected at 20 stations. Statistically significant long-term increases in total nitrogen load were detected at 5 stations, decreases were detected at 4 stations, and no significant trends were detected at 31 stations. Statistically significant long-term increases in flow-adjusted residual concentrations of total phosphorus were detected at 2 stations, decreases were detected at 25 stations, and no significant trends were detected at 13 stations. Statistically significant long-term increases in total phosphorus load were detected at 1 station, decreases were detected at 13 stations, and no significant trends were detected at 26 stations. The mean annual yields were computed from the estimated mean annual loads. Mean annual nitrogen yields are largest for three watersheds in the upper Mississippi Basin; estimated yield of each is greater than 5.0 tons per square mile. Nine stations in the Ohio River Basin have estimated mean annual nitrogen yields greater than 2.0 tons per square mile. Estimated mean annual phosphorus yield is greater than 0.250 ton per square mile at 7 stations, 5 in the Ohio Basin and 2 in the upper Mississippi Basin. Statistically significant trends in annual streamflow were detected at seven stations. Annual streamflow influences trends in load, even when the streamflow trends are not statistically significant.

Mississippi River Basin↗
USGS2013

Time-lapse analysis of methane quantity in Mary Lee group of coal seams using filter-based multiple-point geostatistical simulation

Coal seam degasification and its success are important for controlling methane, and thus for the health and safety of coal miners. During the course of degasification, properties of coal seams change. Thus, the changes in coal reservoir conditions and in-place gas content as well as methane emission potential into mines should be evaluated by examining time-dependent changes and the presence of major heterogeneities and geological discontinuities in the field. In this work, time-lapsed reservoir and fluid storage properties of the New Castle coal seam, Mary Lee/Blue Creek seam, and Jagger seam of Black Warrior Basin, Alabama, were determined from gas and water production history matching and production forecasting of vertical degasification wellbores. These properties were combined with isotherm and other important data to compute gas-in-place (GIP) and its change with time at borehole locations. Time-lapsed training images (TIs) of GIP and GIP difference corresponding to each coal and date were generated by using these point-wise data and Voronoi decomposition on the TI grid, which included faults as discontinuities for expansion of Voronoi regions. Filter-based multiple-point geostatistical simulations, which were preferred in this study due to anisotropies and discontinuities in the area, were used to predict time-lapsed GIP distributions within the study area. Performed simulations were used for mapping spatial time-lapsed methane quantities as well as their uncertainties within the study area. The systematic approach presented in this paper is the first time in literature that history matching, TIs of GIPs and filter simulations are used for degasification performance evaluation and for assessing GIP for mining safety. Results from this study showed that using production history matching of coalbed methane wells to determine time-lapsed reservoir data could be used to compute spatial GIP and representative GIP TIs generated through Voronoi decomposition. Furthermore, performing filter simulations using point-wise data and TIs could be used to predict methane quantity in coal seams subjected to degasification. During the course of the study, it was shown that the material balance of gas produced by wellbores and the GIP reductions in coal seams predicted using filter simulations compared very well, showing the success of filter simulations for continuous variables in this case study. Quantitative results from filter simulations of GIP within the studied area briefly showed that GIP was reduced from an initial ∼73 Bcf (median) to ∼46 Bcf (2011), representing a 37 % decrease and varying spatially through degasification. It is forecasted that there will be an additional ∼2 Bcf reduction in methane quantity between 2011 and 2015. This study and presented results showed that the applied methodology and utilized techniques can be used to map GIP and its change within coal seams after degasification, which can further be used for ventilation design for methane control in coal mines.

Alabama↗
USGS2010

Three-dimensional long-period groundmotion simulations in the upper Mississippi embayment

We employed a 3D velocity model and 3D wave propagation code to simulate long-period ground motions in the upper Mississippi embayment. This region is at risk from large earthquakes in the New Madrid seismic zone (NMSZ) and observational data are sparse, making simulation a valuable tool for predicting the effects of large events. We undertook these simulations to estimate the magnitude of shaking likely to occur and to investigate the influence of the 3D embayment structure and finite-fault mechanics on ground motions. There exist three primary fault zones in the NMSZ, each of which was likely associated with one of the main shocks of the 1811-12 earthquake triplet. For this study, three simulations have been conducted on each major segment, exploring the impact of different epicentral locations and rupture directions on ground motions. The full wave field up to a frequency of 0.5 Hz is computed on a 200 ?? 200 ?? 50-km 3 volume using a staggered-grid finite-difference code. Peak horizontal velocity and bracketed durations were calculated at the free surface. The NMSZ simulations indicate that for the considered bandwidth, finite-fault mechanics such as fault proximity, directivity effect, and slip distribution exert the most control on ground motions. The 3D geologic structure of the upper Mississippi embayment also influences ground motion with indications that amplification is induced by the sharp velocity contrast at the basin edge.

Seismological Research Letters↗